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-rw-r--r--absl/LTS.md13
-rw-r--r--absl/base/BUILD.bazel5
-rw-r--r--absl/base/internal/spinlock_wait.h2
-rw-r--r--absl/strings/BUILD.bazel74
-rw-r--r--absl/strings/CMakeLists.txt44
-rw-r--r--absl/strings/charconv.cc982
-rw-r--r--absl/strings/charconv.h115
-rw-r--r--absl/strings/charconv_benchmark.cc204
-rw-r--r--absl/strings/charconv_test.cc766
-rw-r--r--absl/strings/internal/charconv_bigint.cc357
-rw-r--r--absl/strings/internal/charconv_bigint.h426
-rw-r--r--absl/strings/internal/charconv_bigint_test.cc203
-rw-r--r--absl/strings/internal/charconv_parse.cc496
-rw-r--r--absl/strings/internal/charconv_parse.h96
-rw-r--r--absl/strings/internal/charconv_parse_test.cc357
-rw-r--r--absl/strings/numbers.cc86
-rw-r--r--absl/synchronization/BUILD.bazel6
-rw-r--r--absl/time/BUILD.bazel4
-rw-r--r--absl/time/CMakeLists.txt2
-rw-r--r--absl/time/duration.cc3
-rw-r--r--absl/time/format.cc1
-rw-r--r--absl/time/time.h6
-rw-r--r--absl/types/optional.h2
23 files changed, 4168 insertions, 82 deletions
diff --git a/absl/LTS.md b/absl/LTS.md
new file mode 100644
index 00000000..f7be0997
--- /dev/null
+++ b/absl/LTS.md
@@ -0,0 +1,13 @@
+# Long Term Support (LTS) Branches
+
+This repository contains periodic snapshots of the Abseil codebase that are
+Long Term Support (LTS) branches. An LTS branch allows you to use a known
+version of Abseil without interfering with other projects which may also, in
+turn, use Abseil. (For more information about our releases, see the
+[Abseil Release Management](https://abseil.io/about/releases) guide.
+
+## LTS Branches
+
+The following lists LTS branches and the date they have been released:
+
+* [LTS Branch June 18, 2018](https://github.com/abseil/abseil-cpp/tree/lts_2018_06_18/)
diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index 1e93d97e..d117a4fe 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -371,11 +371,6 @@ cc_test(
size = "small",
srcs = ["internal/sysinfo_test.cc"],
copts = ABSL_TEST_COPTS,
- tags = [
- "no_test_android_arm",
- "no_test_android_arm64",
- "no_test_android_x86",
- ],
deps = [
":base",
"//absl/synchronization",
diff --git a/absl/base/internal/spinlock_wait.h b/absl/base/internal/spinlock_wait.h
index 5f658211..5c6cc7fd 100644
--- a/absl/base/internal/spinlock_wait.h
+++ b/absl/base/internal/spinlock_wait.h
@@ -84,7 +84,7 @@ inline void absl::base_internal::SpinLockWake(std::atomic<uint32_t> *w,
inline void absl::base_internal::SpinLockDelay(
std::atomic<uint32_t> *w, uint32_t value, int loop,
- base_internal::SchedulingMode scheduling_mode) {
+ absl::base_internal::SchedulingMode scheduling_mode) {
AbslInternalSpinLockDelay(w, value, loop, scheduling_mode);
}
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index f06bdc0d..328f52f3 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -32,7 +32,12 @@ cc_library(
name = "strings",
srcs = [
"ascii.cc",
+ "charconv.cc",
"escaping.cc",
+ "internal/charconv_bigint.cc",
+ "internal/charconv_bigint.h",
+ "internal/charconv_parse.cc",
+ "internal/charconv_parse.h",
"internal/memutil.cc",
"internal/memutil.h",
"internal/stl_type_traits.h",
@@ -48,6 +53,7 @@ cc_library(
],
hdrs = [
"ascii.h",
+ "charconv.h",
"escaping.h",
"match.h",
"numbers.h",
@@ -144,11 +150,6 @@ cc_test(
size = "small",
srcs = ["ascii_test.cc"],
copts = ABSL_TEST_COPTS,
- tags = [
- "no_test_android_arm",
- "no_test_android_arm64",
- "no_test_android_x86",
- ],
visibility = ["//visibility:private"],
deps = [
":strings",
@@ -398,12 +399,6 @@ cc_test(
"numbers_test.cc",
],
copts = ABSL_TEST_COPTS,
- tags = [
- "no_test_android_arm",
- "no_test_android_arm64",
- "no_test_android_x86",
- "no_test_loonix",
- ],
visibility = ["//visibility:private"],
deps = [
":strings",
@@ -429,11 +424,6 @@ cc_test(
name = "char_map_test",
srcs = ["internal/char_map_test.cc"],
copts = ABSL_TEST_COPTS,
- tags = [
- "no_test_android_arm",
- "no_test_android_arm64",
- "no_test_android_x86",
- ],
deps = [
":internal",
"@com_google_googletest//:gtest_main",
@@ -450,3 +440,55 @@ cc_test(
"@com_github_google_benchmark//:benchmark_main",
],
)
+
+cc_test(
+ name = "charconv_test",
+ srcs = ["charconv_test.cc"],
+ copts = ABSL_TEST_COPTS,
+ deps = [
+ ":strings",
+ "//absl/base",
+ "@com_google_googletest//:gtest_main",
+ ],
+)
+
+cc_test(
+ name = "charconv_parse_test",
+ srcs = [
+ "internal/charconv_parse.h",
+ "internal/charconv_parse_test.cc",
+ ],
+ copts = ABSL_TEST_COPTS,
+ deps = [
+ ":strings",
+ "//absl/base",
+ "@com_google_googletest//:gtest_main",
+ ],
+)
+
+cc_test(
+ name = "charconv_bigint_test",
+ srcs = [
+ "internal/charconv_bigint.h",
+ "internal/charconv_bigint_test.cc",
+ "internal/charconv_parse.h",
+ ],
+ copts = ABSL_TEST_COPTS,
+ deps = [
+ ":strings",
+ "//absl/base",
+ "@com_google_googletest//:gtest_main",
+ ],
+)
+
+cc_test(
+ name = "charconv_benchmark",
+ srcs = [
+ "charconv_benchmark.cc",
+ ],
+ deps = [
+ ":strings",
+ "//absl/base",
+ "@com_github_google_benchmark//:benchmark_main",
+ ],
+)
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index 9dc47328..cab2c456 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -17,6 +17,7 @@
list(APPEND STRINGS_PUBLIC_HEADERS
"ascii.h"
+ "charconv.h"
"escaping.h"
"match.h"
"numbers.h"
@@ -33,6 +34,8 @@ list(APPEND STRINGS_PUBLIC_HEADERS
list(APPEND STRINGS_INTERNAL_HEADERS
"internal/bits.h"
"internal/char_map.h"
+ "internal/charconv_bigint.h"
+ "internal/charconv_parse.h"
"internal/memutil.h"
"internal/ostringstream.h"
"internal/resize_uninitialized.h"
@@ -47,7 +50,10 @@ list(APPEND STRINGS_INTERNAL_HEADERS
# add string library
list(APPEND STRINGS_SRC
"ascii.cc"
+ "charconv.cc"
"escaping.cc"
+ "internal/charconv_bigint.cc"
+ "internal/charconv_parse.cc"
"internal/memutil.cc"
"internal/memutil.h"
"internal/utf8.cc"
@@ -301,5 +307,43 @@ absl_test(
)
+# test charconv_test
+set(CHARCONV_TEST_SRC "charconv_test.cc")
+set(CHARCONV_TEST_PUBLIC_LIBRARIES absl::strings)
+absl_test(
+ TARGET
+ charconv_test
+ SOURCES
+ ${CHARCONV_TEST_SRC}
+ PUBLIC_LIBRARIES
+ ${CHARCONV_TEST_PUBLIC_LIBRARIES}
+)
+
+
+# test charconv_parse_test
+set(CHARCONV_PARSE_TEST_SRC "internal/charconv_parse_test.cc")
+set(CHARCONV_PARSE_TEST_PUBLIC_LIBRARIES absl::strings)
+
+absl_test(
+ TARGET
+ charconv_parse_test
+ SOURCES
+ ${CHARCONV_PARSE_TEST_SRC}
+ PUBLIC_LIBRARIES
+ ${CHARCONV_PARSE_TEST_PUBLIC_LIBRARIES}
+)
+
+
+# test charconv_bigint_test
+set(CHARCONV_BIGINT_TEST_SRC "internal/charconv_bigint_test.cc")
+set(CHARCONV_BIGINT_TEST_PUBLIC_LIBRARIES absl::strings)
+absl_test(
+ TARGET
+ charconv_bigint_test
+ SOURCES
+ ${CHARCONV_BIGINT_TEST_SRC}
+ PUBLIC_LIBRARIES
+ ${CHARCONV_BIGINT_TEST_PUBLIC_LIBRARIES}
+)
diff --git a/absl/strings/charconv.cc b/absl/strings/charconv.cc
new file mode 100644
index 00000000..08c3947e
--- /dev/null
+++ b/absl/strings/charconv.cc
@@ -0,0 +1,982 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/charconv.h"
+
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstring>
+
+#include "absl/base/casts.h"
+#include "absl/numeric/int128.h"
+#include "absl/strings/internal/bits.h"
+#include "absl/strings/internal/charconv_bigint.h"
+#include "absl/strings/internal/charconv_parse.h"
+
+// The macro ABSL_BIT_PACK_FLOATS is defined on x86-64, where IEEE floating
+// point numbers have the same endianness in memory as a bitfield struct
+// containing the corresponding parts.
+//
+// When set, we replace calls to ldexp() with manual bit packing, which is
+// faster and is unaffected by floating point environment.
+#ifdef ABSL_BIT_PACK_FLOATS
+#error ABSL_BIT_PACK_FLOATS cannot be directly set
+#elif defined(__x86_64__) || defined(_M_X64)
+#define ABSL_BIT_PACK_FLOATS 1
+#endif
+
+// A note about subnormals:
+//
+// The code below talks about "normals" and "subnormals". A normal IEEE float
+// has a fixed-width mantissa and power of two exponent. For example, a normal
+// `double` has a 53-bit mantissa. Because the high bit is always 1, it is not
+// stored in the representation. The implicit bit buys an extra bit of
+// resolution in the datatype.
+//
+// The downside of this scheme is that there is a large gap between DBL_MIN and
+// zero. (Large, at least, relative to the different between DBL_MIN and the
+// next representable number). This gap is softened by the "subnormal" numbers,
+// which have the same power-of-two exponent as DBL_MIN, but no implicit 53rd
+// bit. An all-bits-zero exponent in the encoding represents subnormals. (Zero
+// is represented as a subnormal with an all-bits-zero mantissa.)
+//
+// The code below, in calculations, represents the mantissa as a uint64_t. The
+// end result normally has the 53rd bit set. It represents subnormals by using
+// narrower mantissas.
+
+namespace absl {
+namespace {
+
+template <typename FloatType>
+struct FloatTraits;
+
+template <>
+struct FloatTraits<double> {
+ // The number of mantissa bits in the given float type. This includes the
+ // implied high bit.
+ static constexpr int kTargetMantissaBits = 53;
+
+ // The largest supported IEEE exponent, in our integral mantissa
+ // representation.
+ //
+ // If `m` is the largest possible int kTargetMantissaBits bits wide, then
+ // m * 2**kMaxExponent is exactly equal to DBL_MAX.
+ static constexpr int kMaxExponent = 971;
+
+ // The smallest supported IEEE normal exponent, in our integral mantissa
+ // representation.
+ //
+ // If `m` is the smallest possible int kTargetMantissaBits bits wide, then
+ // m * 2**kMinNormalExponent is exactly equal to DBL_MIN.
+ static constexpr int kMinNormalExponent = -1074;
+
+ static double MakeNan(const char* tagp) {
+ // Support nan no matter which namespace it's in. Some platforms
+ // incorrectly don't put it in namespace std.
+ using namespace std; // NOLINT
+ return nan(tagp);
+ }
+
+ // Builds a nonzero floating point number out of the provided parts.
+ //
+ // This is intended to do the same operation as ldexp(mantissa, exponent),
+ // but using purely integer math, to avoid -ffastmath and floating
+ // point environment issues. Using type punning is also faster. We fall back
+ // to ldexp on a per-platform basis for portability.
+ //
+ // `exponent` must be between kMinNormalExponent and kMaxExponent.
+ //
+ // `mantissa` must either be exactly kTargetMantissaBits wide, in which case
+ // a normal value is made, or it must be less narrow than that, in which case
+ // `exponent` must be exactly kMinNormalExponent, and a subnormal value is
+ // made.
+ static double Make(uint64_t mantissa, int exponent, bool sign) {
+#ifndef ABSL_BIT_PACK_FLOATS
+ // Support ldexp no matter which namespace it's in. Some platforms
+ // incorrectly don't put it in namespace std.
+ using namespace std; // NOLINT
+ return sign ? -ldexp(mantissa, exponent) : ldexp(mantissa, exponent);
+#else
+ constexpr uint64_t kMantissaMask =
+ (uint64_t(1) << (kTargetMantissaBits - 1)) - 1;
+ uint64_t dbl = static_cast<uint64_t>(sign) << 63;
+ if (mantissa > kMantissaMask) {
+ // Normal value.
+ // Adjust by 1023 for the exponent representation bias, and an additional
+ // 52 due to the implied decimal point in the IEEE mantissa represenation.
+ dbl += uint64_t{exponent + 1023u + kTargetMantissaBits - 1} << 52;
+ mantissa &= kMantissaMask;
+ } else {
+ // subnormal value
+ assert(exponent == kMinNormalExponent);
+ }
+ dbl += mantissa;
+ return absl::bit_cast<double>(dbl);
+#endif // ABSL_BIT_PACK_FLOATS
+ }
+};
+
+// Specialization of floating point traits for the `float` type. See the
+// FloatTraits<double> specialization above for meaning of each of the following
+// members and methods.
+template <>
+struct FloatTraits<float> {
+ static constexpr int kTargetMantissaBits = 24;
+ static constexpr int kMaxExponent = 104;
+ static constexpr int kMinNormalExponent = -149;
+ static float MakeNan(const char* tagp) {
+ // Support nanf no matter which namespace it's in. Some platforms
+ // incorrectly don't put it in namespace std.
+ using namespace std; // NOLINT
+ return nanf(tagp);
+ }
+ static float Make(uint32_t mantissa, int exponent, bool sign) {
+#ifndef ABSL_BIT_PACK_FLOATS
+ // Support ldexpf no matter which namespace it's in. Some platforms
+ // incorrectly don't put it in namespace std.
+ using namespace std; // NOLINT
+ return sign ? -ldexpf(mantissa, exponent) : ldexpf(mantissa, exponent);
+#else
+ constexpr uint32_t kMantissaMask =
+ (uint32_t(1) << (kTargetMantissaBits - 1)) - 1;
+ uint32_t flt = static_cast<uint32_t>(sign) << 31;
+ if (mantissa > kMantissaMask) {
+ // Normal value.
+ // Adjust by 127 for the exponent representation bias, and an additional
+ // 23 due to the implied decimal point in the IEEE mantissa represenation.
+ flt += uint32_t{exponent + 127u + kTargetMantissaBits - 1} << 23;
+ mantissa &= kMantissaMask;
+ } else {
+ // subnormal value
+ assert(exponent == kMinNormalExponent);
+ }
+ flt += mantissa;
+ return absl::bit_cast<float>(flt);
+#endif // ABSL_BIT_PACK_FLOATS
+ }
+};
+
+// Decimal-to-binary conversions require coercing powers of 10 into a mantissa
+// and a power of 2. The two helper functions Power10Mantissa(n) and
+// Power10Exponent(n) perform this task. Together, these represent a hand-
+// rolled floating point value which is equal to or just less than 10**n.
+//
+// The return values satisfy two range guarantees:
+//
+// Power10Mantissa(n) * 2**Power10Exponent(n) <= 10**n
+// < (Power10Mantissa(n) + 1) * 2**Power10Exponent(n)
+//
+// 2**63 <= Power10Mantissa(n) < 2**64.
+//
+// Lookups into the power-of-10 table must first check the Power10Overflow() and
+// Power10Underflow() functions, to avoid out-of-bounds table access.
+//
+// Indexes into these tables are biased by -kPower10TableMin, and the table has
+// values in the range [kPower10TableMin, kPower10TableMax].
+extern const uint64_t kPower10MantissaTable[];
+extern const int16_t kPower10ExponentTable[];
+
+// The smallest allowed value for use with the Power10Mantissa() and
+// Power10Exponent() functions below. (If a smaller exponent is needed in
+// calculations, the end result is guaranteed to underflow.)
+constexpr int kPower10TableMin = -342;
+
+// The largest allowed value for use with the Power10Mantissa() and
+// Power10Exponent() functions below. (If a smaller exponent is needed in
+// calculations, the end result is guaranteed to overflow.)
+constexpr int kPower10TableMax = 308;
+
+uint64_t Power10Mantissa(int n) {
+ return kPower10MantissaTable[n - kPower10TableMin];
+}
+
+int Power10Exponent(int n) {
+ return kPower10ExponentTable[n - kPower10TableMin];
+}
+
+// Returns true if n is large enough that 10**n always results in an IEEE
+// overflow.
+bool Power10Overflow(int n) { return n > kPower10TableMax; }
+
+// Returns true if n is small enough that 10**n times a ParsedFloat mantissa
+// always results in an IEEE underflow.
+bool Power10Underflow(int n) { return n < kPower10TableMin; }
+
+// Returns true if Power10Mantissa(n) * 2**Power10Exponent(n) is exactly equal
+// to 10**n numerically. Put another way, this returns true if there is no
+// truncation error in Power10Mantissa(n).
+bool Power10Exact(int n) { return n >= 0 && n <= 27; }
+
+// Sentinel exponent values for representing numbers too large or too close to
+// zero to represent in a double.
+constexpr int kOverflow = 99999;
+constexpr int kUnderflow = -99999;
+
+// Struct representing the calculated conversion result of a positive (nonzero)
+// floating point number.
+//
+// The calculated number is mantissa * 2**exponent (mantissa is treated as an
+// integer.) `mantissa` is chosen to be the correct width for the IEEE float
+// representation being calculated. (`mantissa` will always have the same bit
+// width for normal values, and narrower bit widths for subnormals.)
+//
+// If the result of conversion was an underflow or overflow, exponent is set
+// to kUnderflow or kOverflow.
+struct CalculatedFloat {
+ uint64_t mantissa = 0;
+ int exponent = 0;
+};
+
+// Returns the bit width of the given uint128. (Equivalently, returns 128
+// minus the number of leading zero bits.)
+int BitWidth(uint128 value) {
+ if (Uint128High64(value) == 0) {
+ return 64 - strings_internal::CountLeadingZeros64(Uint128Low64(value));
+ }
+ return 128 - strings_internal::CountLeadingZeros64(Uint128High64(value));
+}
+
+// Calculates how far to the right a mantissa needs to be shifted to create a
+// properly adjusted mantissa for an IEEE floating point number.
+//
+// `mantissa_width` is the bit width of the mantissa to be shifted, and
+// `binary_exponent` is the exponent of the number before the shift.
+//
+// This accounts for subnormal values, and will return a larger-than-normal
+// shift if binary_exponent would otherwise be too low.
+template <typename FloatType>
+int NormalizedShiftSize(int mantissa_width, int binary_exponent) {
+ const int normal_shift =
+ mantissa_width - FloatTraits<FloatType>::kTargetMantissaBits;
+ const int minimum_shift =
+ FloatTraits<FloatType>::kMinNormalExponent - binary_exponent;
+ return std::max(normal_shift, minimum_shift);
+}
+
+// Right shifts a uint128 so that it has the requested bit width. (The
+// resulting value will have 128 - bit_width leading zeroes.) The initial
+// `value` must be wider than the requested bit width.
+//
+// Returns the number of bits shifted.
+int TruncateToBitWidth(int bit_width, uint128* value) {
+ const int current_bit_width = BitWidth(*value);
+ const int shift = current_bit_width - bit_width;
+ *value >>= shift;
+ return shift;
+}
+
+// Checks if the given ParsedFloat represents one of the edge cases that are
+// not dependent on number base: zero, infinity, or NaN. If so, sets *value
+// the appropriate double, and returns true.
+template <typename FloatType>
+bool HandleEdgeCase(const strings_internal::ParsedFloat& input, bool negative,
+ FloatType* value) {
+ if (input.type == strings_internal::FloatType::kNan) {
+ // A bug in both clang and gcc would cause the compiler to optimize away the
+ // buffer we are building below. Declaring the buffer volatile avoids the
+ // issue, and has no measurable performance impact in microbenchmarks.
+ //
+ // https://bugs.llvm.org/show_bug.cgi?id=37778
+ // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86113
+ constexpr ptrdiff_t kNanBufferSize = 128;
+ volatile char n_char_sequence[kNanBufferSize];
+ if (input.subrange_begin == nullptr) {
+ n_char_sequence[0] = '\0';
+ } else {
+ ptrdiff_t nan_size = input.subrange_end - input.subrange_begin;
+ nan_size = std::min(nan_size, kNanBufferSize - 1);
+ std::copy_n(input.subrange_begin, nan_size, n_char_sequence);
+ n_char_sequence[nan_size] = '\0';
+ }
+ char* nan_argument = const_cast<char*>(n_char_sequence);
+ *value = negative ? -FloatTraits<FloatType>::MakeNan(nan_argument)
+ : FloatTraits<FloatType>::MakeNan(nan_argument);
+ return true;
+ }
+ if (input.type == strings_internal::FloatType::kInfinity) {
+ *value = negative ? -std::numeric_limits<FloatType>::infinity()
+ : std::numeric_limits<FloatType>::infinity();
+ return true;
+ }
+ if (input.mantissa == 0) {
+ *value = negative ? -0.0 : 0.0;
+ return true;
+ }
+ return false;
+}
+
+// Given a CalculatedFloat result of a from_chars conversion, generate the
+// correct output values.
+//
+// CalculatedFloat can represent an underflow or overflow, in which case the
+// error code in *result is set. Otherwise, the calculated floating point
+// number is stored in *value.
+template <typename FloatType>
+void EncodeResult(const CalculatedFloat& calculated, bool negative,
+ absl::from_chars_result* result, FloatType* value) {
+ if (calculated.exponent == kOverflow) {
+ result->ec = std::errc::result_out_of_range;
+ *value = negative ? -std::numeric_limits<FloatType>::max()
+ : std::numeric_limits<FloatType>::max();
+ return;
+ } else if (calculated.mantissa == 0 || calculated.exponent == kUnderflow) {
+ result->ec = std::errc::result_out_of_range;
+ *value = negative ? -0.0 : 0.0;
+ return;
+ }
+ *value = FloatTraits<FloatType>::Make(calculated.mantissa,
+ calculated.exponent, negative);
+}
+
+// Returns the given uint128 shifted to the right by `shift` bits, and rounds
+// the remaining bits using round_to_nearest logic. The value is returned as a
+// uint64_t, since this is the type used by this library for storing calculated
+// floating point mantissas.
+//
+// It is expected that the width of the input value shifted by `shift` will
+// be the correct bit-width for the target mantissa, which is strictly narrower
+// than a uint64_t.
+//
+// If `input_exact` is false, then a nonzero error epsilon is assumed. For
+// rounding purposes, the true value being rounded is strictly greater than the
+// input value. The error may represent a single lost carry bit.
+//
+// When input_exact, shifted bits of the form 1000000... represent a tie, which
+// is broken by rounding to even -- the rounding direction is chosen so the low
+// bit of the returned value is 0.
+//
+// When !input_exact, shifted bits of the form 10000000... represent a value
+// strictly greater than one half (due to the error epsilon), and so ties are
+// always broken by rounding up.
+//
+// When !input_exact, shifted bits of the form 01111111... are uncertain;
+// the true value may or may not be greater than 10000000..., due to the
+// possible lost carry bit. The correct rounding direction is unknown. In this
+// case, the result is rounded down, and `output_exact` is set to false.
+//
+// Zero and negative values of `shift` are accepted, in which case the word is
+// shifted left, as necessary.
+uint64_t ShiftRightAndRound(uint128 value, int shift, bool input_exact,
+ bool* output_exact) {
+ if (shift <= 0) {
+ *output_exact = input_exact;
+ return static_cast<uint64_t>(value << -shift);
+ }
+ if (shift >= 128) {
+ // Exponent is so small that we are shifting away all significant bits.
+ // Answer will not be representable, even as a subnormal, so return a zero
+ // mantissa (which represents underflow).
+ *output_exact = true;
+ return 0;
+ }
+
+ *output_exact = true;
+ const uint128 shift_mask = (uint128(1) << shift) - 1;
+ const uint128 halfway_point = uint128(1) << (shift - 1);
+
+ const uint128 shifted_bits = value & shift_mask;
+ value >>= shift;
+ if (shifted_bits > halfway_point) {
+ // Shifted bits greater than 10000... require rounding up.
+ return static_cast<uint64_t>(value + 1);
+ }
+ if (shifted_bits == halfway_point) {
+ // In exact mode, shifted bits of 10000... mean we're exactly halfway
+ // between two numbers, and we must round to even. So only round up if
+ // the low bit of `value` is set.
+ //
+ // In inexact mode, the nonzero error means the actual value is greater
+ // than the halfway point and we must alway round up.
+ if ((value & 1) == 1 || !input_exact) {
+ ++value;
+ }
+ return static_cast<uint64_t>(value);
+ }
+ if (!input_exact && shifted_bits == halfway_point - 1) {
+ // Rounding direction is unclear, due to error.
+ *output_exact = false;
+ }
+ // Otherwise, round down.
+ return static_cast<uint64_t>(value);
+}
+
+// Checks if a floating point guess needs to be rounded up, using high precision
+// math.
+//
+// `guess_mantissa` and `guess_exponent` represent a candidate guess for the
+// number represented by `parsed_decimal`.
+//
+// The exact number represented by `parsed_decimal` must lie between the two
+// numbers:
+// A = `guess_mantissa * 2**guess_exponent`
+// B = `(guess_mantissa + 1) * 2**guess_exponent`
+//
+// This function returns false if `A` is the better guess, and true if `B` is
+// the better guess, with rounding ties broken by rounding to even.
+bool MustRoundUp(uint64_t guess_mantissa, int guess_exponent,
+ const strings_internal::ParsedFloat& parsed_decimal) {
+ // 768 is the number of digits needed in the worst case. We could determine a
+ // better limit dynamically based on the value of parsed_decimal.exponent.
+ // This would optimize pathological input cases only. (Sane inputs won't have
+ // hundreds of digits of mantissa.)
+ absl::strings_internal::BigUnsigned<84> exact_mantissa;
+ int exact_exponent = exact_mantissa.ReadFloatMantissa(parsed_decimal, 768);
+
+ // Adjust the `guess` arguments to be halfway between A and B.
+ guess_mantissa = guess_mantissa * 2 + 1;
+ guess_exponent -= 1;
+
+ // In our comparison:
+ // lhs = exact = exact_mantissa * 10**exact_exponent
+ // = exact_mantissa * 5**exact_exponent * 2**exact_exponent
+ // rhs = guess = guess_mantissa * 2**guess_exponent
+ //
+ // Because we are doing integer math, we can't directly deal with negative
+ // exponents. We instead move these to the other side of the inequality.
+ absl::strings_internal::BigUnsigned<84>& lhs = exact_mantissa;
+ int comparison;
+ if (exact_exponent >= 0) {
+ lhs.MultiplyByFiveToTheNth(exact_exponent);
+ absl::strings_internal::BigUnsigned<84> rhs(guess_mantissa);
+ // There are powers of 2 on both sides of the inequality; reduce this to
+ // a single bit-shift.
+ if (exact_exponent > guess_exponent) {
+ lhs.ShiftLeft(exact_exponent - guess_exponent);
+ } else {
+ rhs.ShiftLeft(guess_exponent - exact_exponent);
+ }
+ comparison = Compare(lhs, rhs);
+ } else {
+ // Move the power of 5 to the other side of the equation, giving us:
+ // lhs = exact_mantissa * 2**exact_exponent
+ // rhs = guess_mantissa * 5**(-exact_exponent) * 2**guess_exponent
+ absl::strings_internal::BigUnsigned<84> rhs =
+ absl::strings_internal::BigUnsigned<84>::FiveToTheNth(-exact_exponent);
+ rhs.MultiplyBy(guess_mantissa);
+ if (exact_exponent > guess_exponent) {
+ lhs.ShiftLeft(exact_exponent - guess_exponent);
+ } else {
+ rhs.ShiftLeft(guess_exponent - exact_exponent);
+ }
+ comparison = Compare(lhs, rhs);
+ }
+ if (comparison < 0) {
+ return false;
+ } else if (comparison > 0) {
+ return true;
+ } else {
+ // When lhs == rhs, the decimal input is exactly between A and B.
+ // Round towards even -- round up only if the low bit of the initial
+ // `guess_mantissa` was a 1. We shifted guess_mantissa left 1 bit at
+ // the beginning of this function, so test the 2nd bit here.
+ return (guess_mantissa & 2) == 2;
+ }
+}
+
+// Constructs a CalculatedFloat from a given mantissa and exponent, but
+// with the following normalizations applied:
+//
+// If rounding has caused mantissa to increase just past the allowed bit
+// width, shift and adjust exponent.
+//
+// If exponent is too high, sets kOverflow.
+//
+// If mantissa is zero (representing a non-zero value not representable, even
+// as a subnormal), sets kUnderflow.
+template <typename FloatType>
+CalculatedFloat CalculatedFloatFromRawValues(uint64_t mantissa, int exponent) {
+ CalculatedFloat result;
+ if (mantissa == uint64_t(1) << FloatTraits<FloatType>::kTargetMantissaBits) {
+ mantissa >>= 1;
+ exponent += 1;
+ }
+ if (exponent > FloatTraits<FloatType>::kMaxExponent) {
+ result.exponent = kOverflow;
+ } else if (mantissa == 0) {
+ result.exponent = kUnderflow;
+ } else {
+ result.exponent = exponent;
+ result.mantissa = mantissa;
+ }
+ return result;
+}
+
+template <typename FloatType>
+CalculatedFloat CalculateFromParsedHexadecimal(
+ const strings_internal::ParsedFloat& parsed_hex) {
+ uint64_t mantissa = parsed_hex.mantissa;
+ int exponent = parsed_hex.exponent;
+ int mantissa_width = 64 - strings_internal::CountLeadingZeros64(mantissa);
+ const int shift = NormalizedShiftSize<FloatType>(mantissa_width, exponent);
+ bool result_exact;
+ exponent += shift;
+ mantissa = ShiftRightAndRound(mantissa, shift,
+ /* input exact= */ true, &result_exact);
+ // ParseFloat handles rounding in the hexadecimal case, so we don't have to
+ // check `result_exact` here.
+ return CalculatedFloatFromRawValues<FloatType>(mantissa, exponent);
+}
+
+template <typename FloatType>
+CalculatedFloat CalculateFromParsedDecimal(
+ const strings_internal::ParsedFloat& parsed_decimal) {
+ CalculatedFloat result;
+
+ // Large or small enough decimal exponents will always result in overflow
+ // or underflow.
+ if (Power10Underflow(parsed_decimal.exponent)) {
+ result.exponent = kUnderflow;
+ return result;
+ } else if (Power10Overflow(parsed_decimal.exponent)) {
+ result.exponent = kOverflow;
+ return result;
+ }
+
+ // Otherwise convert our power of 10 into a power of 2 times an integer
+ // mantissa, and multiply this by our parsed decimal mantissa.
+ uint128 wide_binary_mantissa = parsed_decimal.mantissa;
+ wide_binary_mantissa *= Power10Mantissa(parsed_decimal.exponent);
+ int binary_exponent = Power10Exponent(parsed_decimal.exponent);
+
+ // Discard bits that are inaccurate due to truncation error. The magic
+ // `mantissa_width` constants below are justified in charconv_algorithm.md.
+ // They represent the number of bits in `wide_binary_mantissa` that are
+ // guaranteed to be unaffected by error propagation.
+ bool mantissa_exact;
+ int mantissa_width;
+ if (parsed_decimal.subrange_begin) {
+ // Truncated mantissa
+ mantissa_width = 58;
+ mantissa_exact = false;
+ binary_exponent +=
+ TruncateToBitWidth(mantissa_width, &wide_binary_mantissa);
+ } else if (!Power10Exact(parsed_decimal.exponent)) {
+ // Exact mantissa, truncated power of ten
+ mantissa_width = 63;
+ mantissa_exact = false;
+ binary_exponent +=
+ TruncateToBitWidth(mantissa_width, &wide_binary_mantissa);
+ } else {
+ // Product is exact
+ mantissa_width = BitWidth(wide_binary_mantissa);
+ mantissa_exact = true;
+ }
+
+ // Shift into an FloatType-sized mantissa, and round to nearest.
+ const int shift =
+ NormalizedShiftSize<FloatType>(mantissa_width, binary_exponent);
+ bool result_exact;
+ binary_exponent += shift;
+ uint64_t binary_mantissa = ShiftRightAndRound(wide_binary_mantissa, shift,
+ mantissa_exact, &result_exact);
+ if (!result_exact) {
+ // We could not determine the rounding direction using int128 math. Use
+ // full resolution math instead.
+ if (MustRoundUp(binary_mantissa, binary_exponent, parsed_decimal)) {
+ binary_mantissa += 1;
+ }
+ }
+
+ return CalculatedFloatFromRawValues<FloatType>(binary_mantissa,
+ binary_exponent);
+}
+
+template <typename FloatType>
+from_chars_result FromCharsImpl(const char* first, const char* last,
+ FloatType& value, chars_format fmt_flags) {
+ from_chars_result result;
+ result.ptr = first; // overwritten on successful parse
+ result.ec = std::errc();
+
+ bool negative = false;
+ if (first != last && *first == '-') {
+ ++first;
+ negative = true;
+ }
+ // If the `hex` flag is *not* set, then we will accept a 0x prefix and try
+ // to parse a hexadecimal float.
+ if ((fmt_flags & chars_format::hex) == chars_format{} && last - first >= 2 &&
+ *first == '0' && (first[1] == 'x' || first[1] == 'X')) {
+ const char* hex_first = first + 2;
+ strings_internal::ParsedFloat hex_parse =
+ strings_internal::ParseFloat<16>(hex_first, last, fmt_flags);
+ if (hex_parse.end == nullptr ||
+ hex_parse.type != strings_internal::FloatType::kNumber) {
+ // Either we failed to parse a hex float after the "0x", or we read
+ // "0xinf" or "0xnan" which we don't want to match.
+ //
+ // However, a std::string that begins with "0x" also begins with "0", which
+ // is normally a valid match for the number zero. So we want these
+ // strings to match zero unless fmt_flags is `scientific`. (This flag
+ // means an exponent is required, which the std::string "0" does not have.)
+ if (fmt_flags == chars_format::scientific) {
+ result.ec = std::errc::invalid_argument;
+ } else {
+ result.ptr = first + 1;
+ value = negative ? -0.0 : 0.0;
+ }
+ return result;
+ }
+ // We matched a value.
+ result.ptr = hex_parse.end;
+ if (HandleEdgeCase(hex_parse, negative, &value)) {
+ return result;
+ }
+ CalculatedFloat calculated =
+ CalculateFromParsedHexadecimal<FloatType>(hex_parse);
+ EncodeResult(calculated, negative, &result, &value);
+ return result;
+ }
+ // Otherwise, we choose the number base based on the flags.
+ if ((fmt_flags & chars_format::hex) == chars_format::hex) {
+ strings_internal::ParsedFloat hex_parse =
+ strings_internal::ParseFloat<16>(first, last, fmt_flags);
+ if (hex_parse.end == nullptr) {
+ result.ec = std::errc::invalid_argument;
+ return result;
+ }
+ result.ptr = hex_parse.end;
+ if (HandleEdgeCase(hex_parse, negative, &value)) {
+ return result;
+ }
+ CalculatedFloat calculated =
+ CalculateFromParsedHexadecimal<FloatType>(hex_parse);
+ EncodeResult(calculated, negative, &result, &value);
+ return result;
+ } else {
+ strings_internal::ParsedFloat decimal_parse =
+ strings_internal::ParseFloat<10>(first, last, fmt_flags);
+ if (decimal_parse.end == nullptr) {
+ result.ec = std::errc::invalid_argument;
+ return result;
+ }
+ result.ptr = decimal_parse.end;
+ if (HandleEdgeCase(decimal_parse, negative, &value)) {
+ return result;
+ }
+ CalculatedFloat calculated =
+ CalculateFromParsedDecimal<FloatType>(decimal_parse);
+ EncodeResult(calculated, negative, &result, &value);
+ return result;
+ }
+ return result;
+}
+} // namespace
+
+from_chars_result from_chars(const char* first, const char* last, double& value,
+ chars_format fmt) {
+ return FromCharsImpl(first, last, value, fmt);
+}
+
+from_chars_result from_chars(const char* first, const char* last, float& value,
+ chars_format fmt) {
+ return FromCharsImpl(first, last, value, fmt);
+}
+
+namespace {
+
+// Table of powers of 10, from kPower10TableMin to kPower10TableMax.
+//
+// kPower10MantissaTable[i - kPower10TableMin] stores the 64-bit mantissa (high
+// bit always on), and kPower10ExponentTable[i - kPower10TableMin] stores the
+// power-of-two exponent. For a given number i, this gives the unique mantissa
+// and exponent such that mantissa * 2**exponent <= 10**i < (mantissa + 1) *
+// 2**exponent.
+
+const uint64_t kPower10MantissaTable[] = {
+ 0xeef453d6923bd65aU, 0x9558b4661b6565f8U, 0xbaaee17fa23ebf76U,
+ 0xe95a99df8ace6f53U, 0x91d8a02bb6c10594U, 0xb64ec836a47146f9U,
+ 0xe3e27a444d8d98b7U, 0x8e6d8c6ab0787f72U, 0xb208ef855c969f4fU,
+ 0xde8b2b66b3bc4723U, 0x8b16fb203055ac76U, 0xaddcb9e83c6b1793U,
+ 0xd953e8624b85dd78U, 0x87d4713d6f33aa6bU, 0xa9c98d8ccb009506U,
+ 0xd43bf0effdc0ba48U, 0x84a57695fe98746dU, 0xa5ced43b7e3e9188U,
+ 0xcf42894a5dce35eaU, 0x818995ce7aa0e1b2U, 0xa1ebfb4219491a1fU,
+ 0xca66fa129f9b60a6U, 0xfd00b897478238d0U, 0x9e20735e8cb16382U,
+ 0xc5a890362fddbc62U, 0xf712b443bbd52b7bU, 0x9a6bb0aa55653b2dU,
+ 0xc1069cd4eabe89f8U, 0xf148440a256e2c76U, 0x96cd2a865764dbcaU,
+ 0xbc807527ed3e12bcU, 0xeba09271e88d976bU, 0x93445b8731587ea3U,
+ 0xb8157268fdae9e4cU, 0xe61acf033d1a45dfU, 0x8fd0c16206306babU,
+ 0xb3c4f1ba87bc8696U, 0xe0b62e2929aba83cU, 0x8c71dcd9ba0b4925U,
+ 0xaf8e5410288e1b6fU, 0xdb71e91432b1a24aU, 0x892731ac9faf056eU,
+ 0xab70fe17c79ac6caU, 0xd64d3d9db981787dU, 0x85f0468293f0eb4eU,
+ 0xa76c582338ed2621U, 0xd1476e2c07286faaU, 0x82cca4db847945caU,
+ 0xa37fce126597973cU, 0xcc5fc196fefd7d0cU, 0xff77b1fcbebcdc4fU,
+ 0x9faacf3df73609b1U, 0xc795830d75038c1dU, 0xf97ae3d0d2446f25U,
+ 0x9becce62836ac577U, 0xc2e801fb244576d5U, 0xf3a20279ed56d48aU,
+ 0x9845418c345644d6U, 0xbe5691ef416bd60cU, 0xedec366b11c6cb8fU,
+ 0x94b3a202eb1c3f39U, 0xb9e08a83a5e34f07U, 0xe858ad248f5c22c9U,
+ 0x91376c36d99995beU, 0xb58547448ffffb2dU, 0xe2e69915b3fff9f9U,
+ 0x8dd01fad907ffc3bU, 0xb1442798f49ffb4aU, 0xdd95317f31c7fa1dU,
+ 0x8a7d3eef7f1cfc52U, 0xad1c8eab5ee43b66U, 0xd863b256369d4a40U,
+ 0x873e4f75e2224e68U, 0xa90de3535aaae202U, 0xd3515c2831559a83U,
+ 0x8412d9991ed58091U, 0xa5178fff668ae0b6U, 0xce5d73ff402d98e3U,
+ 0x80fa687f881c7f8eU, 0xa139029f6a239f72U, 0xc987434744ac874eU,
+ 0xfbe9141915d7a922U, 0x9d71ac8fada6c9b5U, 0xc4ce17b399107c22U,
+ 0xf6019da07f549b2bU, 0x99c102844f94e0fbU, 0xc0314325637a1939U,
+ 0xf03d93eebc589f88U, 0x96267c7535b763b5U, 0xbbb01b9283253ca2U,
+ 0xea9c227723ee8bcbU, 0x92a1958a7675175fU, 0xb749faed14125d36U,
+ 0xe51c79a85916f484U, 0x8f31cc0937ae58d2U, 0xb2fe3f0b8599ef07U,
+ 0xdfbdcece67006ac9U, 0x8bd6a141006042bdU, 0xaecc49914078536dU,
+ 0xda7f5bf590966848U, 0x888f99797a5e012dU, 0xaab37fd7d8f58178U,
+ 0xd5605fcdcf32e1d6U, 0x855c3be0a17fcd26U, 0xa6b34ad8c9dfc06fU,
+ 0xd0601d8efc57b08bU, 0x823c12795db6ce57U, 0xa2cb1717b52481edU,
+ 0xcb7ddcdda26da268U, 0xfe5d54150b090b02U, 0x9efa548d26e5a6e1U,
+ 0xc6b8e9b0709f109aU, 0xf867241c8cc6d4c0U, 0x9b407691d7fc44f8U,
+ 0xc21094364dfb5636U, 0xf294b943e17a2bc4U, 0x979cf3ca6cec5b5aU,
+ 0xbd8430bd08277231U, 0xece53cec4a314ebdU, 0x940f4613ae5ed136U,
+ 0xb913179899f68584U, 0xe757dd7ec07426e5U, 0x9096ea6f3848984fU,
+ 0xb4bca50b065abe63U, 0xe1ebce4dc7f16dfbU, 0x8d3360f09cf6e4bdU,
+ 0xb080392cc4349decU, 0xdca04777f541c567U, 0x89e42caaf9491b60U,
+ 0xac5d37d5b79b6239U, 0xd77485cb25823ac7U, 0x86a8d39ef77164bcU,
+ 0xa8530886b54dbdebU, 0xd267caa862a12d66U, 0x8380dea93da4bc60U,
+ 0xa46116538d0deb78U, 0xcd795be870516656U, 0x806bd9714632dff6U,
+ 0xa086cfcd97bf97f3U, 0xc8a883c0fdaf7df0U, 0xfad2a4b13d1b5d6cU,
+ 0x9cc3a6eec6311a63U, 0xc3f490aa77bd60fcU, 0xf4f1b4d515acb93bU,
+ 0x991711052d8bf3c5U, 0xbf5cd54678eef0b6U, 0xef340a98172aace4U,
+ 0x9580869f0e7aac0eU, 0xbae0a846d2195712U, 0xe998d258869facd7U,
+ 0x91ff83775423cc06U, 0xb67f6455292cbf08U, 0xe41f3d6a7377eecaU,
+ 0x8e938662882af53eU, 0xb23867fb2a35b28dU, 0xdec681f9f4c31f31U,
+ 0x8b3c113c38f9f37eU, 0xae0b158b4738705eU, 0xd98ddaee19068c76U,
+ 0x87f8a8d4cfa417c9U, 0xa9f6d30a038d1dbcU, 0xd47487cc8470652bU,
+ 0x84c8d4dfd2c63f3bU, 0xa5fb0a17c777cf09U, 0xcf79cc9db955c2ccU,
+ 0x81ac1fe293d599bfU, 0xa21727db38cb002fU, 0xca9cf1d206fdc03bU,
+ 0xfd442e4688bd304aU, 0x9e4a9cec15763e2eU, 0xc5dd44271ad3cdbaU,
+ 0xf7549530e188c128U, 0x9a94dd3e8cf578b9U, 0xc13a148e3032d6e7U,
+ 0xf18899b1bc3f8ca1U, 0x96f5600f15a7b7e5U, 0xbcb2b812db11a5deU,
+ 0xebdf661791d60f56U, 0x936b9fcebb25c995U, 0xb84687c269ef3bfbU,
+ 0xe65829b3046b0afaU, 0x8ff71a0fe2c2e6dcU, 0xb3f4e093db73a093U,
+ 0xe0f218b8d25088b8U, 0x8c974f7383725573U, 0xafbd2350644eeacfU,
+ 0xdbac6c247d62a583U, 0x894bc396ce5da772U, 0xab9eb47c81f5114fU,
+ 0xd686619ba27255a2U, 0x8613fd0145877585U, 0xa798fc4196e952e7U,
+ 0xd17f3b51fca3a7a0U, 0x82ef85133de648c4U, 0xa3ab66580d5fdaf5U,
+ 0xcc963fee10b7d1b3U, 0xffbbcfe994e5c61fU, 0x9fd561f1fd0f9bd3U,
+ 0xc7caba6e7c5382c8U, 0xf9bd690a1b68637bU, 0x9c1661a651213e2dU,
+ 0xc31bfa0fe5698db8U, 0xf3e2f893dec3f126U, 0x986ddb5c6b3a76b7U,
+ 0xbe89523386091465U, 0xee2ba6c0678b597fU, 0x94db483840b717efU,
+ 0xba121a4650e4ddebU, 0xe896a0d7e51e1566U, 0x915e2486ef32cd60U,
+ 0xb5b5ada8aaff80b8U, 0xe3231912d5bf60e6U, 0x8df5efabc5979c8fU,
+ 0xb1736b96b6fd83b3U, 0xddd0467c64bce4a0U, 0x8aa22c0dbef60ee4U,
+ 0xad4ab7112eb3929dU, 0xd89d64d57a607744U, 0x87625f056c7c4a8bU,
+ 0xa93af6c6c79b5d2dU, 0xd389b47879823479U, 0x843610cb4bf160cbU,
+ 0xa54394fe1eedb8feU, 0xce947a3da6a9273eU, 0x811ccc668829b887U,
+ 0xa163ff802a3426a8U, 0xc9bcff6034c13052U, 0xfc2c3f3841f17c67U,
+ 0x9d9ba7832936edc0U, 0xc5029163f384a931U, 0xf64335bcf065d37dU,
+ 0x99ea0196163fa42eU, 0xc06481fb9bcf8d39U, 0xf07da27a82c37088U,
+ 0x964e858c91ba2655U, 0xbbe226efb628afeaU, 0xeadab0aba3b2dbe5U,
+ 0x92c8ae6b464fc96fU, 0xb77ada0617e3bbcbU, 0xe55990879ddcaabdU,
+ 0x8f57fa54c2a9eab6U, 0xb32df8e9f3546564U, 0xdff9772470297ebdU,
+ 0x8bfbea76c619ef36U, 0xaefae51477a06b03U, 0xdab99e59958885c4U,
+ 0x88b402f7fd75539bU, 0xaae103b5fcd2a881U, 0xd59944a37c0752a2U,
+ 0x857fcae62d8493a5U, 0xa6dfbd9fb8e5b88eU, 0xd097ad07a71f26b2U,
+ 0x825ecc24c873782fU, 0xa2f67f2dfa90563bU, 0xcbb41ef979346bcaU,
+ 0xfea126b7d78186bcU, 0x9f24b832e6b0f436U, 0xc6ede63fa05d3143U,
+ 0xf8a95fcf88747d94U, 0x9b69dbe1b548ce7cU, 0xc24452da229b021bU,
+ 0xf2d56790ab41c2a2U, 0x97c560ba6b0919a5U, 0xbdb6b8e905cb600fU,
+ 0xed246723473e3813U, 0x9436c0760c86e30bU, 0xb94470938fa89bceU,
+ 0xe7958cb87392c2c2U, 0x90bd77f3483bb9b9U, 0xb4ecd5f01a4aa828U,
+ 0xe2280b6c20dd5232U, 0x8d590723948a535fU, 0xb0af48ec79ace837U,
+ 0xdcdb1b2798182244U, 0x8a08f0f8bf0f156bU, 0xac8b2d36eed2dac5U,
+ 0xd7adf884aa879177U, 0x86ccbb52ea94baeaU, 0xa87fea27a539e9a5U,
+ 0xd29fe4b18e88640eU, 0x83a3eeeef9153e89U, 0xa48ceaaab75a8e2bU,
+ 0xcdb02555653131b6U, 0x808e17555f3ebf11U, 0xa0b19d2ab70e6ed6U,
+ 0xc8de047564d20a8bU, 0xfb158592be068d2eU, 0x9ced737bb6c4183dU,
+ 0xc428d05aa4751e4cU, 0xf53304714d9265dfU, 0x993fe2c6d07b7fabU,
+ 0xbf8fdb78849a5f96U, 0xef73d256a5c0f77cU, 0x95a8637627989aadU,
+ 0xbb127c53b17ec159U, 0xe9d71b689dde71afU, 0x9226712162ab070dU,
+ 0xb6b00d69bb55c8d1U, 0xe45c10c42a2b3b05U, 0x8eb98a7a9a5b04e3U,
+ 0xb267ed1940f1c61cU, 0xdf01e85f912e37a3U, 0x8b61313bbabce2c6U,
+ 0xae397d8aa96c1b77U, 0xd9c7dced53c72255U, 0x881cea14545c7575U,
+ 0xaa242499697392d2U, 0xd4ad2dbfc3d07787U, 0x84ec3c97da624ab4U,
+ 0xa6274bbdd0fadd61U, 0xcfb11ead453994baU, 0x81ceb32c4b43fcf4U,
+ 0xa2425ff75e14fc31U, 0xcad2f7f5359a3b3eU, 0xfd87b5f28300ca0dU,
+ 0x9e74d1b791e07e48U, 0xc612062576589ddaU, 0xf79687aed3eec551U,
+ 0x9abe14cd44753b52U, 0xc16d9a0095928a27U, 0xf1c90080baf72cb1U,
+ 0x971da05074da7beeU, 0xbce5086492111aeaU, 0xec1e4a7db69561a5U,
+ 0x9392ee8e921d5d07U, 0xb877aa3236a4b449U, 0xe69594bec44de15bU,
+ 0x901d7cf73ab0acd9U, 0xb424dc35095cd80fU, 0xe12e13424bb40e13U,
+ 0x8cbccc096f5088cbU, 0xafebff0bcb24aafeU, 0xdbe6fecebdedd5beU,
+ 0x89705f4136b4a597U, 0xabcc77118461cefcU, 0xd6bf94d5e57a42bcU,
+ 0x8637bd05af6c69b5U, 0xa7c5ac471b478423U, 0xd1b71758e219652bU,
+ 0x83126e978d4fdf3bU, 0xa3d70a3d70a3d70aU, 0xccccccccccccccccU,
+ 0x8000000000000000U, 0xa000000000000000U, 0xc800000000000000U,
+ 0xfa00000000000000U, 0x9c40000000000000U, 0xc350000000000000U,
+ 0xf424000000000000U, 0x9896800000000000U, 0xbebc200000000000U,
+ 0xee6b280000000000U, 0x9502f90000000000U, 0xba43b74000000000U,
+ 0xe8d4a51000000000U, 0x9184e72a00000000U, 0xb5e620f480000000U,
+ 0xe35fa931a0000000U, 0x8e1bc9bf04000000U, 0xb1a2bc2ec5000000U,
+ 0xde0b6b3a76400000U, 0x8ac7230489e80000U, 0xad78ebc5ac620000U,
+ 0xd8d726b7177a8000U, 0x878678326eac9000U, 0xa968163f0a57b400U,
+ 0xd3c21bcecceda100U, 0x84595161401484a0U, 0xa56fa5b99019a5c8U,
+ 0xcecb8f27f4200f3aU, 0x813f3978f8940984U, 0xa18f07d736b90be5U,
+ 0xc9f2c9cd04674edeU, 0xfc6f7c4045812296U, 0x9dc5ada82b70b59dU,
+ 0xc5371912364ce305U, 0xf684df56c3e01bc6U, 0x9a130b963a6c115cU,
+ 0xc097ce7bc90715b3U, 0xf0bdc21abb48db20U, 0x96769950b50d88f4U,
+ 0xbc143fa4e250eb31U, 0xeb194f8e1ae525fdU, 0x92efd1b8d0cf37beU,
+ 0xb7abc627050305adU, 0xe596b7b0c643c719U, 0x8f7e32ce7bea5c6fU,
+ 0xb35dbf821ae4f38bU, 0xe0352f62a19e306eU, 0x8c213d9da502de45U,
+ 0xaf298d050e4395d6U, 0xdaf3f04651d47b4cU, 0x88d8762bf324cd0fU,
+ 0xab0e93b6efee0053U, 0xd5d238a4abe98068U, 0x85a36366eb71f041U,
+ 0xa70c3c40a64e6c51U, 0xd0cf4b50cfe20765U, 0x82818f1281ed449fU,
+ 0xa321f2d7226895c7U, 0xcbea6f8ceb02bb39U, 0xfee50b7025c36a08U,
+ 0x9f4f2726179a2245U, 0xc722f0ef9d80aad6U, 0xf8ebad2b84e0d58bU,
+ 0x9b934c3b330c8577U, 0xc2781f49ffcfa6d5U, 0xf316271c7fc3908aU,
+ 0x97edd871cfda3a56U, 0xbde94e8e43d0c8ecU, 0xed63a231d4c4fb27U,
+ 0x945e455f24fb1cf8U, 0xb975d6b6ee39e436U, 0xe7d34c64a9c85d44U,
+ 0x90e40fbeea1d3a4aU, 0xb51d13aea4a488ddU, 0xe264589a4dcdab14U,
+ 0x8d7eb76070a08aecU, 0xb0de65388cc8ada8U, 0xdd15fe86affad912U,
+ 0x8a2dbf142dfcc7abU, 0xacb92ed9397bf996U, 0xd7e77a8f87daf7fbU,
+ 0x86f0ac99b4e8dafdU, 0xa8acd7c0222311bcU, 0xd2d80db02aabd62bU,
+ 0x83c7088e1aab65dbU, 0xa4b8cab1a1563f52U, 0xcde6fd5e09abcf26U,
+ 0x80b05e5ac60b6178U, 0xa0dc75f1778e39d6U, 0xc913936dd571c84cU,
+ 0xfb5878494ace3a5fU, 0x9d174b2dcec0e47bU, 0xc45d1df942711d9aU,
+ 0xf5746577930d6500U, 0x9968bf6abbe85f20U, 0xbfc2ef456ae276e8U,
+ 0xefb3ab16c59b14a2U, 0x95d04aee3b80ece5U, 0xbb445da9ca61281fU,
+ 0xea1575143cf97226U, 0x924d692ca61be758U, 0xb6e0c377cfa2e12eU,
+ 0xe498f455c38b997aU, 0x8edf98b59a373fecU, 0xb2977ee300c50fe7U,
+ 0xdf3d5e9bc0f653e1U, 0x8b865b215899f46cU, 0xae67f1e9aec07187U,
+ 0xda01ee641a708de9U, 0x884134fe908658b2U, 0xaa51823e34a7eedeU,
+ 0xd4e5e2cdc1d1ea96U, 0x850fadc09923329eU, 0xa6539930bf6bff45U,
+ 0xcfe87f7cef46ff16U, 0x81f14fae158c5f6eU, 0xa26da3999aef7749U,
+ 0xcb090c8001ab551cU, 0xfdcb4fa002162a63U, 0x9e9f11c4014dda7eU,
+ 0xc646d63501a1511dU, 0xf7d88bc24209a565U, 0x9ae757596946075fU,
+ 0xc1a12d2fc3978937U, 0xf209787bb47d6b84U, 0x9745eb4d50ce6332U,
+ 0xbd176620a501fbffU, 0xec5d3fa8ce427affU, 0x93ba47c980e98cdfU,
+ 0xb8a8d9bbe123f017U, 0xe6d3102ad96cec1dU, 0x9043ea1ac7e41392U,
+ 0xb454e4a179dd1877U, 0xe16a1dc9d8545e94U, 0x8ce2529e2734bb1dU,
+ 0xb01ae745b101e9e4U, 0xdc21a1171d42645dU, 0x899504ae72497ebaU,
+ 0xabfa45da0edbde69U, 0xd6f8d7509292d603U, 0x865b86925b9bc5c2U,
+ 0xa7f26836f282b732U, 0xd1ef0244af2364ffU, 0x8335616aed761f1fU,
+ 0xa402b9c5a8d3a6e7U, 0xcd036837130890a1U, 0x802221226be55a64U,
+ 0xa02aa96b06deb0fdU, 0xc83553c5c8965d3dU, 0xfa42a8b73abbf48cU,
+ 0x9c69a97284b578d7U, 0xc38413cf25e2d70dU, 0xf46518c2ef5b8cd1U,
+ 0x98bf2f79d5993802U, 0xbeeefb584aff8603U, 0xeeaaba2e5dbf6784U,
+ 0x952ab45cfa97a0b2U, 0xba756174393d88dfU, 0xe912b9d1478ceb17U,
+ 0x91abb422ccb812eeU, 0xb616a12b7fe617aaU, 0xe39c49765fdf9d94U,
+ 0x8e41ade9fbebc27dU, 0xb1d219647ae6b31cU, 0xde469fbd99a05fe3U,
+ 0x8aec23d680043beeU, 0xada72ccc20054ae9U, 0xd910f7ff28069da4U,
+ 0x87aa9aff79042286U, 0xa99541bf57452b28U, 0xd3fa922f2d1675f2U,
+ 0x847c9b5d7c2e09b7U, 0xa59bc234db398c25U, 0xcf02b2c21207ef2eU,
+ 0x8161afb94b44f57dU, 0xa1ba1ba79e1632dcU, 0xca28a291859bbf93U,
+ 0xfcb2cb35e702af78U, 0x9defbf01b061adabU, 0xc56baec21c7a1916U,
+ 0xf6c69a72a3989f5bU, 0x9a3c2087a63f6399U, 0xc0cb28a98fcf3c7fU,
+ 0xf0fdf2d3f3c30b9fU, 0x969eb7c47859e743U, 0xbc4665b596706114U,
+ 0xeb57ff22fc0c7959U, 0x9316ff75dd87cbd8U, 0xb7dcbf5354e9beceU,
+ 0xe5d3ef282a242e81U, 0x8fa475791a569d10U, 0xb38d92d760ec4455U,
+ 0xe070f78d3927556aU, 0x8c469ab843b89562U, 0xaf58416654a6babbU,
+ 0xdb2e51bfe9d0696aU, 0x88fcf317f22241e2U, 0xab3c2fddeeaad25aU,
+ 0xd60b3bd56a5586f1U, 0x85c7056562757456U, 0xa738c6bebb12d16cU,
+ 0xd106f86e69d785c7U, 0x82a45b450226b39cU, 0xa34d721642b06084U,
+ 0xcc20ce9bd35c78a5U, 0xff290242c83396ceU, 0x9f79a169bd203e41U,
+ 0xc75809c42c684dd1U, 0xf92e0c3537826145U, 0x9bbcc7a142b17ccbU,
+ 0xc2abf989935ddbfeU, 0xf356f7ebf83552feU, 0x98165af37b2153deU,
+ 0xbe1bf1b059e9a8d6U, 0xeda2ee1c7064130cU, 0x9485d4d1c63e8be7U,
+ 0xb9a74a0637ce2ee1U, 0xe8111c87c5c1ba99U, 0x910ab1d4db9914a0U,
+ 0xb54d5e4a127f59c8U, 0xe2a0b5dc971f303aU, 0x8da471a9de737e24U,
+ 0xb10d8e1456105dadU, 0xdd50f1996b947518U, 0x8a5296ffe33cc92fU,
+ 0xace73cbfdc0bfb7bU, 0xd8210befd30efa5aU, 0x8714a775e3e95c78U,
+ 0xa8d9d1535ce3b396U, 0xd31045a8341ca07cU, 0x83ea2b892091e44dU,
+ 0xa4e4b66b68b65d60U, 0xce1de40642e3f4b9U, 0x80d2ae83e9ce78f3U,
+ 0xa1075a24e4421730U, 0xc94930ae1d529cfcU, 0xfb9b7cd9a4a7443cU,
+ 0x9d412e0806e88aa5U, 0xc491798a08a2ad4eU, 0xf5b5d7ec8acb58a2U,
+ 0x9991a6f3d6bf1765U, 0xbff610b0cc6edd3fU, 0xeff394dcff8a948eU,
+ 0x95f83d0a1fb69cd9U, 0xbb764c4ca7a4440fU, 0xea53df5fd18d5513U,
+ 0x92746b9be2f8552cU, 0xb7118682dbb66a77U, 0xe4d5e82392a40515U,
+ 0x8f05b1163ba6832dU, 0xb2c71d5bca9023f8U, 0xdf78e4b2bd342cf6U,
+ 0x8bab8eefb6409c1aU, 0xae9672aba3d0c320U, 0xda3c0f568cc4f3e8U,
+ 0x8865899617fb1871U, 0xaa7eebfb9df9de8dU, 0xd51ea6fa85785631U,
+ 0x8533285c936b35deU, 0xa67ff273b8460356U, 0xd01fef10a657842cU,
+ 0x8213f56a67f6b29bU, 0xa298f2c501f45f42U, 0xcb3f2f7642717713U,
+ 0xfe0efb53d30dd4d7U, 0x9ec95d1463e8a506U, 0xc67bb4597ce2ce48U,
+ 0xf81aa16fdc1b81daU, 0x9b10a4e5e9913128U, 0xc1d4ce1f63f57d72U,
+ 0xf24a01a73cf2dccfU, 0x976e41088617ca01U, 0xbd49d14aa79dbc82U,
+ 0xec9c459d51852ba2U, 0x93e1ab8252f33b45U, 0xb8da1662e7b00a17U,
+ 0xe7109bfba19c0c9dU, 0x906a617d450187e2U, 0xb484f9dc9641e9daU,
+ 0xe1a63853bbd26451U, 0x8d07e33455637eb2U, 0xb049dc016abc5e5fU,
+ 0xdc5c5301c56b75f7U, 0x89b9b3e11b6329baU, 0xac2820d9623bf429U,
+ 0xd732290fbacaf133U, 0x867f59a9d4bed6c0U, 0xa81f301449ee8c70U,
+ 0xd226fc195c6a2f8cU, 0x83585d8fd9c25db7U, 0xa42e74f3d032f525U,
+ 0xcd3a1230c43fb26fU, 0x80444b5e7aa7cf85U, 0xa0555e361951c366U,
+ 0xc86ab5c39fa63440U, 0xfa856334878fc150U, 0x9c935e00d4b9d8d2U,
+ 0xc3b8358109e84f07U, 0xf4a642e14c6262c8U, 0x98e7e9cccfbd7dbdU,
+ 0xbf21e44003acdd2cU, 0xeeea5d5004981478U, 0x95527a5202df0ccbU,
+ 0xbaa718e68396cffdU, 0xe950df20247c83fdU, 0x91d28b7416cdd27eU,
+ 0xb6472e511c81471dU, 0xe3d8f9e563a198e5U, 0x8e679c2f5e44ff8fU,
+};
+
+const int16_t kPower10ExponentTable[] = {
+ -1200, -1196, -1193, -1190, -1186, -1183, -1180, -1176, -1173, -1170, -1166,
+ -1163, -1160, -1156, -1153, -1150, -1146, -1143, -1140, -1136, -1133, -1130,
+ -1127, -1123, -1120, -1117, -1113, -1110, -1107, -1103, -1100, -1097, -1093,
+ -1090, -1087, -1083, -1080, -1077, -1073, -1070, -1067, -1063, -1060, -1057,
+ -1053, -1050, -1047, -1043, -1040, -1037, -1034, -1030, -1027, -1024, -1020,
+ -1017, -1014, -1010, -1007, -1004, -1000, -997, -994, -990, -987, -984,
+ -980, -977, -974, -970, -967, -964, -960, -957, -954, -950, -947,
+ -944, -940, -937, -934, -931, -927, -924, -921, -917, -914, -911,
+ -907, -904, -901, -897, -894, -891, -887, -884, -881, -877, -874,
+ -871, -867, -864, -861, -857, -854, -851, -847, -844, -841, -838,
+ -834, -831, -828, -824, -821, -818, -814, -811, -808, -804, -801,
+ -798, -794, -791, -788, -784, -781, -778, -774, -771, -768, -764,
+ -761, -758, -754, -751, -748, -744, -741, -738, -735, -731, -728,
+ -725, -721, -718, -715, -711, -708, -705, -701, -698, -695, -691,
+ -688, -685, -681, -678, -675, -671, -668, -665, -661, -658, -655,
+ -651, -648, -645, -642, -638, -635, -632, -628, -625, -622, -618,
+ -615, -612, -608, -605, -602, -598, -595, -592, -588, -585, -582,
+ -578, -575, -572, -568, -565, -562, -558, -555, -552, -549, -545,
+ -542, -539, -535, -532, -529, -525, -522, -519, -515, -512, -509,
+ -505, -502, -499, -495, -492, -489, -485, -482, -479, -475, -472,
+ -469, -465, -462, -459, -455, -452, -449, -446, -442, -439, -436,
+ -432, -429, -426, -422, -419, -416, -412, -409, -406, -402, -399,
+ -396, -392, -389, -386, -382, -379, -376, -372, -369, -366, -362,
+ -359, -356, -353, -349, -346, -343, -339, -336, -333, -329, -326,
+ -323, -319, -316, -313, -309, -306, -303, -299, -296, -293, -289,
+ -286, -283, -279, -276, -273, -269, -266, -263, -259, -256, -253,
+ -250, -246, -243, -240, -236, -233, -230, -226, -223, -220, -216,
+ -213, -210, -206, -203, -200, -196, -193, -190, -186, -183, -180,
+ -176, -173, -170, -166, -163, -160, -157, -153, -150, -147, -143,
+ -140, -137, -133, -130, -127, -123, -120, -117, -113, -110, -107,
+ -103, -100, -97, -93, -90, -87, -83, -80, -77, -73, -70,
+ -67, -63, -60, -57, -54, -50, -47, -44, -40, -37, -34,
+ -30, -27, -24, -20, -17, -14, -10, -7, -4, 0, 3,
+ 6, 10, 13, 16, 20, 23, 26, 30, 33, 36, 39,
+ 43, 46, 49, 53, 56, 59, 63, 66, 69, 73, 76,
+ 79, 83, 86, 89, 93, 96, 99, 103, 106, 109, 113,
+ 116, 119, 123, 126, 129, 132, 136, 139, 142, 146, 149,
+ 152, 156, 159, 162, 166, 169, 172, 176, 179, 182, 186,
+ 189, 192, 196, 199, 202, 206, 209, 212, 216, 219, 222,
+ 226, 229, 232, 235, 239, 242, 245, 249, 252, 255, 259,
+ 262, 265, 269, 272, 275, 279, 282, 285, 289, 292, 295,
+ 299, 302, 305, 309, 312, 315, 319, 322, 325, 328, 332,
+ 335, 338, 342, 345, 348, 352, 355, 358, 362, 365, 368,
+ 372, 375, 378, 382, 385, 388, 392, 395, 398, 402, 405,
+ 408, 412, 415, 418, 422, 425, 428, 431, 435, 438, 441,
+ 445, 448, 451, 455, 458, 461, 465, 468, 471, 475, 478,
+ 481, 485, 488, 491, 495, 498, 501, 505, 508, 511, 515,
+ 518, 521, 524, 528, 531, 534, 538, 541, 544, 548, 551,
+ 554, 558, 561, 564, 568, 571, 574, 578, 581, 584, 588,
+ 591, 594, 598, 601, 604, 608, 611, 614, 617, 621, 624,
+ 627, 631, 634, 637, 641, 644, 647, 651, 654, 657, 661,
+ 664, 667, 671, 674, 677, 681, 684, 687, 691, 694, 697,
+ 701, 704, 707, 711, 714, 717, 720, 724, 727, 730, 734,
+ 737, 740, 744, 747, 750, 754, 757, 760, 764, 767, 770,
+ 774, 777, 780, 784, 787, 790, 794, 797, 800, 804, 807,
+ 810, 813, 817, 820, 823, 827, 830, 833, 837, 840, 843,
+ 847, 850, 853, 857, 860, 863, 867, 870, 873, 877, 880,
+ 883, 887, 890, 893, 897, 900, 903, 907, 910, 913, 916,
+ 920, 923, 926, 930, 933, 936, 940, 943, 946, 950, 953,
+ 956, 960,
+};
+
+} // namespace
+} // namespace absl
diff --git a/absl/strings/charconv.h b/absl/strings/charconv.h
new file mode 100644
index 00000000..3e313679
--- /dev/null
+++ b/absl/strings/charconv.h
@@ -0,0 +1,115 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_CHARCONV_H_
+#define ABSL_STRINGS_CHARCONV_H_
+
+#include <system_error> // NOLINT(build/c++11)
+
+namespace absl {
+
+// Workalike compatibilty version of std::chars_format from C++17.
+//
+// This is an bitfield enumerator which can be passed to absl::from_chars to
+// configure the std::string-to-float conversion.
+enum class chars_format {
+ scientific = 1,
+ fixed = 2,
+ hex = 4,
+ general = fixed | scientific,
+};
+
+// The return result of a std::string-to-number conversion.
+//
+// `ec` will be set to `invalid_argument` if a well-formed number was not found
+// at the start of the input range, `result_out_of_range` if a well-formed
+// number was found, but it was out of the representable range of the requested
+// type, or to std::errc() otherwise.
+//
+// If a well-formed number was found, `ptr` is set to one past the sequence of
+// characters that were successfully parsed. If none was found, `ptr` is set
+// to the `first` argument to from_chars.
+struct from_chars_result {
+ const char* ptr;
+ std::errc ec;
+};
+
+// Workalike compatibilty version of std::from_chars from C++17. Currently
+// this only supports the `double` and `float` types.
+//
+// This interface incorporates the proposed resolutions for library issues
+// DR 3800 and DR 3801. If these are adopted with different wording,
+// Abseil's behavior will change to match the standard. (The behavior most
+// likely to change is for DR 3801, which says what `value` will be set to in
+// the case of overflow and underflow. Code that wants to avoid possible
+// breaking changes in this area should not depend on `value` when the returned
+// from_chars_result indicates a range error.)
+//
+// Searches the range [first, last) for the longest matching pattern beginning
+// at `first` that represents a floating point number. If one is found, store
+// the result in `value`.
+//
+// The matching pattern format is almost the same as that of strtod(), except
+// that C locale is not respected, and an initial '+' character in the input
+// range will never be matched.
+//
+// If `fmt` is set, it must be one of the enumerator values of the chars_format.
+// (This is despite the fact that chars_format is a bitmask type.) If set to
+// `scientific`, a matching number must contain an exponent. If set to `fixed`,
+// then an exponent will never match. (For example, the std::string "1e5" will be
+// parsed as "1".) If set to `hex`, then a hexadecimal float is parsed in the
+// format that strtod() accepts, except that a "0x" prefix is NOT matched.
+// (In particular, in `hex` mode, the input "0xff" results in the largest
+// matching pattern "0".)
+absl::from_chars_result from_chars(const char* first, const char* last,
+ double& value, // NOLINT
+ chars_format fmt = chars_format::general);
+
+absl::from_chars_result from_chars(const char* first, const char* last,
+ float& value, // NOLINT
+ chars_format fmt = chars_format::general);
+
+// std::chars_format is specified as a bitmask type, which means the following
+// operations must be provided:
+inline constexpr chars_format operator&(chars_format lhs, chars_format rhs) {
+ return static_cast<chars_format>(static_cast<int>(lhs) &
+ static_cast<int>(rhs));
+}
+inline constexpr chars_format operator|(chars_format lhs, chars_format rhs) {
+ return static_cast<chars_format>(static_cast<int>(lhs) |
+ static_cast<int>(rhs));
+}
+inline constexpr chars_format operator^(chars_format lhs, chars_format rhs) {
+ return static_cast<chars_format>(static_cast<int>(lhs) ^
+ static_cast<int>(rhs));
+}
+inline constexpr chars_format operator~(chars_format arg) {
+ return static_cast<chars_format>(~static_cast<int>(arg));
+}
+inline chars_format& operator&=(chars_format& lhs, chars_format rhs) {
+ lhs = lhs & rhs;
+ return lhs;
+}
+inline chars_format& operator|=(chars_format& lhs, chars_format rhs) {
+ lhs = lhs | rhs;
+ return lhs;
+}
+inline chars_format& operator^=(chars_format& lhs, chars_format rhs) {
+ lhs = lhs ^ rhs;
+ return lhs;
+}
+
+} // namespace absl
+
+#endif // ABSL_STRINGS_CHARCONV_H_
diff --git a/absl/strings/charconv_benchmark.cc b/absl/strings/charconv_benchmark.cc
new file mode 100644
index 00000000..fd83f44e
--- /dev/null
+++ b/absl/strings/charconv_benchmark.cc
@@ -0,0 +1,204 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/charconv.h"
+
+#include <cstdlib>
+#include <cstring>
+#include <string>
+
+#include "benchmark/benchmark.h"
+
+namespace {
+
+void BM_Strtod_Pi(benchmark::State& state) {
+ const char* pi = "3.14159";
+ for (auto s : state) {
+ benchmark::DoNotOptimize(pi);
+ benchmark::DoNotOptimize(strtod(pi, nullptr));
+ }
+}
+BENCHMARK(BM_Strtod_Pi);
+
+void BM_Absl_Pi(benchmark::State& state) {
+ const char* pi = "3.14159";
+ const char* pi_end = pi + strlen(pi);
+ for (auto s : state) {
+ benchmark::DoNotOptimize(pi);
+ double v;
+ absl::from_chars(pi, pi_end, v);
+ benchmark::DoNotOptimize(v);
+ }
+}
+BENCHMARK(BM_Absl_Pi);
+
+void BM_Strtod_Pi_float(benchmark::State& state) {
+ const char* pi = "3.14159";
+ for (auto s : state) {
+ benchmark::DoNotOptimize(pi);
+ benchmark::DoNotOptimize(strtof(pi, nullptr));
+ }
+}
+BENCHMARK(BM_Strtod_Pi_float);
+
+void BM_Absl_Pi_float(benchmark::State& state) {
+ const char* pi = "3.14159";
+ const char* pi_end = pi + strlen(pi);
+ for (auto s : state) {
+ benchmark::DoNotOptimize(pi);
+ float v;
+ absl::from_chars(pi, pi_end, v);
+ benchmark::DoNotOptimize(v);
+ }
+}
+BENCHMARK(BM_Absl_Pi_float);
+
+void BM_Strtod_HardLarge(benchmark::State& state) {
+ const char* num = "272104041512242479.e200";
+ for (auto s : state) {
+ benchmark::DoNotOptimize(num);
+ benchmark::DoNotOptimize(strtod(num, nullptr));
+ }
+}
+BENCHMARK(BM_Strtod_HardLarge);
+
+void BM_Absl_HardLarge(benchmark::State& state) {
+ const char* numstr = "272104041512242479.e200";
+ const char* numstr_end = numstr + strlen(numstr);
+ for (auto s : state) {
+ benchmark::DoNotOptimize(numstr);
+ double v;
+ absl::from_chars(numstr, numstr_end, v);
+ benchmark::DoNotOptimize(v);
+ }
+}
+BENCHMARK(BM_Absl_HardLarge);
+
+void BM_Strtod_HardSmall(benchmark::State& state) {
+ const char* num = "94080055902682397.e-242";
+ for (auto s : state) {
+ benchmark::DoNotOptimize(num);
+ benchmark::DoNotOptimize(strtod(num, nullptr));
+ }
+}
+BENCHMARK(BM_Strtod_HardSmall);
+
+void BM_Absl_HardSmall(benchmark::State& state) {
+ const char* numstr = "94080055902682397.e-242";
+ const char* numstr_end = numstr + strlen(numstr);
+ for (auto s : state) {
+ benchmark::DoNotOptimize(numstr);
+ double v;
+ absl::from_chars(numstr, numstr_end, v);
+ benchmark::DoNotOptimize(v);
+ }
+}
+BENCHMARK(BM_Absl_HardSmall);
+
+void BM_Strtod_HugeMantissa(benchmark::State& state) {
+ std::string huge(200, '3');
+ const char* num = huge.c_str();
+ for (auto s : state) {
+ benchmark::DoNotOptimize(num);
+ benchmark::DoNotOptimize(strtod(num, nullptr));
+ }
+}
+BENCHMARK(BM_Strtod_HugeMantissa);
+
+void BM_Absl_HugeMantissa(benchmark::State& state) {
+ std::string huge(200, '3');
+ const char* num = huge.c_str();
+ const char* num_end = num + 200;
+ for (auto s : state) {
+ benchmark::DoNotOptimize(num);
+ double v;
+ absl::from_chars(num, num_end, v);
+ benchmark::DoNotOptimize(v);
+ }
+}
+BENCHMARK(BM_Absl_HugeMantissa);
+
+std::string MakeHardCase(int length) {
+ // The number 1.1521...e-297 is exactly halfway between 12345 * 2**-1000 and
+ // the next larger representable number. The digits of this number are in
+ // the std::string below.
+ const std::string digits =
+ "1."
+ "152113937042223790993097181572444900347587985074226836242307364987727724"
+ "831384300183638649152607195040591791364113930628852279348613864894524591"
+ "272746490313676832900762939595690019745859128071117417798540258114233761"
+ "012939937017879509401007964861774960297319002612457273148497158989073482"
+ "171377406078223015359818300988676687994537274548940612510414856761641652"
+ "513434981938564294004070500716200446656421722229202383105446378511678258"
+ "370570631774499359748259931676320916632111681001853983492795053244971606"
+ "922718923011680846577744433974087653954904214152517799883551075537146316"
+ "168973685866425605046988661997658648354773076621610279716804960009043764"
+ "038392994055171112475093876476783502487512538082706095923790634572014823"
+ "78877699375152587890625" +
+ std::string(5000, '0');
+ // generate the hard cases on either side for the given length.
+ // Lengths between 3 and 1000 are reasonable.
+ return digits.substr(0, length) + "1e-297";
+}
+
+void BM_Strtod_Big_And_Difficult(benchmark::State& state) {
+ std::string testcase = MakeHardCase(state.range(0));
+ const char* begin = testcase.c_str();
+ for (auto s : state) {
+ benchmark::DoNotOptimize(begin);
+ benchmark::DoNotOptimize(strtod(begin, nullptr));
+ }
+}
+BENCHMARK(BM_Strtod_Big_And_Difficult)->Range(3, 5000);
+
+void BM_Absl_Big_And_Difficult(benchmark::State& state) {
+ std::string testcase = MakeHardCase(state.range(0));
+ const char* begin = testcase.c_str();
+ const char* end = begin + testcase.size();
+ for (auto s : state) {
+ benchmark::DoNotOptimize(begin);
+ double v;
+ absl::from_chars(begin, end, v);
+ benchmark::DoNotOptimize(v);
+ }
+}
+BENCHMARK(BM_Absl_Big_And_Difficult)->Range(3, 5000);
+
+} // namespace
+
+// ------------------------------------------------------------------------
+// Benchmark Time CPU Iterations
+// ------------------------------------------------------------------------
+// BM_Strtod_Pi 96 ns 96 ns 6337454
+// BM_Absl_Pi 35 ns 35 ns 20031996
+// BM_Strtod_Pi_float 91 ns 91 ns 7745851
+// BM_Absl_Pi_float 35 ns 35 ns 20430298
+// BM_Strtod_HardLarge 133 ns 133 ns 5288341
+// BM_Absl_HardLarge 181 ns 181 ns 3855615
+// BM_Strtod_HardSmall 279 ns 279 ns 2517243
+// BM_Absl_HardSmall 287 ns 287 ns 2458744
+// BM_Strtod_HugeMantissa 433 ns 433 ns 1604293
+// BM_Absl_HugeMantissa 160 ns 160 ns 4403671
+// BM_Strtod_Big_And_Difficult/3 236 ns 236 ns 2942496
+// BM_Strtod_Big_And_Difficult/8 232 ns 232 ns 2983796
+// BM_Strtod_Big_And_Difficult/64 437 ns 437 ns 1591951
+// BM_Strtod_Big_And_Difficult/512 1738 ns 1738 ns 402519
+// BM_Strtod_Big_And_Difficult/4096 3943 ns 3943 ns 176128
+// BM_Strtod_Big_And_Difficult/5000 4397 ns 4397 ns 157878
+// BM_Absl_Big_And_Difficult/3 39 ns 39 ns 17799583
+// BM_Absl_Big_And_Difficult/8 43 ns 43 ns 16096859
+// BM_Absl_Big_And_Difficult/64 550 ns 550 ns 1259717
+// BM_Absl_Big_And_Difficult/512 4167 ns 4167 ns 171414
+// BM_Absl_Big_And_Difficult/4096 9160 ns 9159 ns 76297
+// BM_Absl_Big_And_Difficult/5000 9738 ns 9738 ns 70140
diff --git a/absl/strings/charconv_test.cc b/absl/strings/charconv_test.cc
new file mode 100644
index 00000000..f8d71cc6
--- /dev/null
+++ b/absl/strings/charconv_test.cc
@@ -0,0 +1,766 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/charconv.h"
+
+#include <cstdlib>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/str_cat.h"
+
+#ifdef _MSC_FULL_VER
+#define ABSL_COMPILER_DOES_EXACT_ROUNDING 0
+#define ABSL_STRTOD_HANDLES_NAN_CORRECTLY 0
+#else
+#define ABSL_COMPILER_DOES_EXACT_ROUNDING 1
+#define ABSL_STRTOD_HANDLES_NAN_CORRECTLY 1
+#endif
+
+namespace {
+
+#if ABSL_COMPILER_DOES_EXACT_ROUNDING
+
+// Tests that the given std::string is accepted by absl::from_chars, and that it
+// converts exactly equal to the given number.
+void TestDoubleParse(absl::string_view str, double expected_number) {
+ SCOPED_TRACE(str);
+ double actual_number = 0.0;
+ absl::from_chars_result result =
+ absl::from_chars(str.data(), str.data() + str.length(), actual_number);
+ EXPECT_EQ(result.ec, std::errc());
+ EXPECT_EQ(result.ptr, str.data() + str.length());
+ EXPECT_EQ(actual_number, expected_number);
+}
+
+void TestFloatParse(absl::string_view str, float expected_number) {
+ SCOPED_TRACE(str);
+ float actual_number = 0.0;
+ absl::from_chars_result result =
+ absl::from_chars(str.data(), str.data() + str.length(), actual_number);
+ EXPECT_EQ(result.ec, std::errc());
+ EXPECT_EQ(result.ptr, str.data() + str.length());
+ EXPECT_EQ(actual_number, expected_number);
+}
+
+// Tests that the given double or single precision floating point literal is
+// parsed correctly by absl::from_chars.
+//
+// These convenience macros assume that the C++ compiler being used also does
+// fully correct decimal-to-binary conversions.
+#define FROM_CHARS_TEST_DOUBLE(number) \
+ { \
+ TestDoubleParse(#number, number); \
+ TestDoubleParse("-" #number, -number); \
+ }
+
+#define FROM_CHARS_TEST_FLOAT(number) \
+ { \
+ TestFloatParse(#number, number##f); \
+ TestFloatParse("-" #number, -number##f); \
+ }
+
+TEST(FromChars, NearRoundingCases) {
+ // Cases from "A Program for Testing IEEE Decimal-Binary Conversion"
+ // by Vern Paxson.
+
+ // Forms that should round towards zero. (These are the hardest cases for
+ // each decimal mantissa size.)
+ FROM_CHARS_TEST_DOUBLE(5.e125);
+ FROM_CHARS_TEST_DOUBLE(69.e267);
+ FROM_CHARS_TEST_DOUBLE(999.e-026);
+ FROM_CHARS_TEST_DOUBLE(7861.e-034);
+ FROM_CHARS_TEST_DOUBLE(75569.e-254);
+ FROM_CHARS_TEST_DOUBLE(928609.e-261);
+ FROM_CHARS_TEST_DOUBLE(9210917.e080);
+ FROM_CHARS_TEST_DOUBLE(84863171.e114);
+ FROM_CHARS_TEST_DOUBLE(653777767.e273);
+ FROM_CHARS_TEST_DOUBLE(5232604057.e-298);
+ FROM_CHARS_TEST_DOUBLE(27235667517.e-109);
+ FROM_CHARS_TEST_DOUBLE(653532977297.e-123);
+ FROM_CHARS_TEST_DOUBLE(3142213164987.e-294);
+ FROM_CHARS_TEST_DOUBLE(46202199371337.e-072);
+ FROM_CHARS_TEST_DOUBLE(231010996856685.e-073);
+ FROM_CHARS_TEST_DOUBLE(9324754620109615.e212);
+ FROM_CHARS_TEST_DOUBLE(78459735791271921.e049);
+ FROM_CHARS_TEST_DOUBLE(272104041512242479.e200);
+ FROM_CHARS_TEST_DOUBLE(6802601037806061975.e198);
+ FROM_CHARS_TEST_DOUBLE(20505426358836677347.e-221);
+ FROM_CHARS_TEST_DOUBLE(836168422905420598437.e-234);
+ FROM_CHARS_TEST_DOUBLE(4891559871276714924261.e222);
+ FROM_CHARS_TEST_FLOAT(5.e-20);
+ FROM_CHARS_TEST_FLOAT(67.e14);
+ FROM_CHARS_TEST_FLOAT(985.e15);
+ FROM_CHARS_TEST_FLOAT(7693.e-42);
+ FROM_CHARS_TEST_FLOAT(55895.e-16);
+ FROM_CHARS_TEST_FLOAT(996622.e-44);
+ FROM_CHARS_TEST_FLOAT(7038531.e-32);
+ FROM_CHARS_TEST_FLOAT(60419369.e-46);
+ FROM_CHARS_TEST_FLOAT(702990899.e-20);
+ FROM_CHARS_TEST_FLOAT(6930161142.e-48);
+ FROM_CHARS_TEST_FLOAT(25933168707.e-13);
+ FROM_CHARS_TEST_FLOAT(596428896559.e20);
+
+ // Similarly, forms that should round away from zero.
+ FROM_CHARS_TEST_DOUBLE(9.e-265);
+ FROM_CHARS_TEST_DOUBLE(85.e-037);
+ FROM_CHARS_TEST_DOUBLE(623.e100);
+ FROM_CHARS_TEST_DOUBLE(3571.e263);
+ FROM_CHARS_TEST_DOUBLE(81661.e153);
+ FROM_CHARS_TEST_DOUBLE(920657.e-023);
+ FROM_CHARS_TEST_DOUBLE(4603285.e-024);
+ FROM_CHARS_TEST_DOUBLE(87575437.e-309);
+ FROM_CHARS_TEST_DOUBLE(245540327.e122);
+ FROM_CHARS_TEST_DOUBLE(6138508175.e120);
+ FROM_CHARS_TEST_DOUBLE(83356057653.e193);
+ FROM_CHARS_TEST_DOUBLE(619534293513.e124);
+ FROM_CHARS_TEST_DOUBLE(2335141086879.e218);
+ FROM_CHARS_TEST_DOUBLE(36167929443327.e-159);
+ FROM_CHARS_TEST_DOUBLE(609610927149051.e-255);
+ FROM_CHARS_TEST_DOUBLE(3743626360493413.e-165);
+ FROM_CHARS_TEST_DOUBLE(94080055902682397.e-242);
+ FROM_CHARS_TEST_DOUBLE(899810892172646163.e283);
+ FROM_CHARS_TEST_DOUBLE(7120190517612959703.e120);
+ FROM_CHARS_TEST_DOUBLE(25188282901709339043.e-252);
+ FROM_CHARS_TEST_DOUBLE(308984926168550152811.e-052);
+ FROM_CHARS_TEST_DOUBLE(6372891218502368041059.e064);
+ FROM_CHARS_TEST_FLOAT(3.e-23);
+ FROM_CHARS_TEST_FLOAT(57.e18);
+ FROM_CHARS_TEST_FLOAT(789.e-35);
+ FROM_CHARS_TEST_FLOAT(2539.e-18);
+ FROM_CHARS_TEST_FLOAT(76173.e28);
+ FROM_CHARS_TEST_FLOAT(887745.e-11);
+ FROM_CHARS_TEST_FLOAT(5382571.e-37);
+ FROM_CHARS_TEST_FLOAT(82381273.e-35);
+ FROM_CHARS_TEST_FLOAT(750486563.e-38);
+ FROM_CHARS_TEST_FLOAT(3752432815.e-39);
+ FROM_CHARS_TEST_FLOAT(75224575729.e-45);
+ FROM_CHARS_TEST_FLOAT(459926601011.e15);
+}
+
+#undef FROM_CHARS_TEST_DOUBLE
+#undef FROM_CHARS_TEST_FLOAT
+#endif
+
+float ToFloat(absl::string_view s) {
+ float f;
+ absl::from_chars(s.data(), s.data() + s.size(), f);
+ return f;
+}
+
+double ToDouble(absl::string_view s) {
+ double d;
+ absl::from_chars(s.data(), s.data() + s.size(), d);
+ return d;
+}
+
+// A duplication of the test cases in "NearRoundingCases" above, but with
+// expected values expressed with integers, using ldexp/ldexpf. These test
+// cases will work even on compilers that do not accurately round floating point
+// literals.
+TEST(FromChars, NearRoundingCasesExplicit) {
+ EXPECT_EQ(ToDouble("5.e125"), ldexp(6653062250012735, 365));
+ EXPECT_EQ(ToDouble("69.e267"), ldexp(4705683757438170, 841));
+ EXPECT_EQ(ToDouble("999.e-026"), ldexp(6798841691080350, -129));
+ EXPECT_EQ(ToDouble("7861.e-034"), ldexp(8975675289889240, -153));
+ EXPECT_EQ(ToDouble("75569.e-254"), ldexp(6091718967192243, -880));
+ EXPECT_EQ(ToDouble("928609.e-261"), ldexp(7849264900213743, -900));
+ EXPECT_EQ(ToDouble("9210917.e080"), ldexp(8341110837370930, 236));
+ EXPECT_EQ(ToDouble("84863171.e114"), ldexp(4625202867375927, 353));
+ EXPECT_EQ(ToDouble("653777767.e273"), ldexp(5068902999763073, 884));
+ EXPECT_EQ(ToDouble("5232604057.e-298"), ldexp(5741343011915040, -1010));
+ EXPECT_EQ(ToDouble("27235667517.e-109"), ldexp(6707124626673586, -380));
+ EXPECT_EQ(ToDouble("653532977297.e-123"), ldexp(7078246407265384, -422));
+ EXPECT_EQ(ToDouble("3142213164987.e-294"), ldexp(8219991337640559, -988));
+ EXPECT_EQ(ToDouble("46202199371337.e-072"), ldexp(5224462102115359, -246));
+ EXPECT_EQ(ToDouble("231010996856685.e-073"), ldexp(5224462102115359, -247));
+ EXPECT_EQ(ToDouble("9324754620109615.e212"), ldexp(5539753864394442, 705));
+ EXPECT_EQ(ToDouble("78459735791271921.e049"), ldexp(8388176519442766, 166));
+ EXPECT_EQ(ToDouble("272104041512242479.e200"), ldexp(5554409530847367, 670));
+ EXPECT_EQ(ToDouble("6802601037806061975.e198"), ldexp(5554409530847367, 668));
+ EXPECT_EQ(ToDouble("20505426358836677347.e-221"),
+ ldexp(4524032052079546, -722));
+ EXPECT_EQ(ToDouble("836168422905420598437.e-234"),
+ ldexp(5070963299887562, -760));
+ EXPECT_EQ(ToDouble("4891559871276714924261.e222"),
+ ldexp(6452687840519111, 757));
+ EXPECT_EQ(ToFloat("5.e-20"), ldexpf(15474250, -88));
+ EXPECT_EQ(ToFloat("67.e14"), ldexpf(12479722, 29));
+ EXPECT_EQ(ToFloat("985.e15"), ldexpf(14333636, 36));
+ EXPECT_EQ(ToFloat("7693.e-42"), ldexpf(10979816, -150));
+ EXPECT_EQ(ToFloat("55895.e-16"), ldexpf(12888509, -61));
+ EXPECT_EQ(ToFloat("996622.e-44"), ldexpf(14224264, -150));
+ EXPECT_EQ(ToFloat("7038531.e-32"), ldexpf(11420669, -107));
+ EXPECT_EQ(ToFloat("60419369.e-46"), ldexpf(8623340, -150));
+ EXPECT_EQ(ToFloat("702990899.e-20"), ldexpf(16209866, -61));
+ EXPECT_EQ(ToFloat("6930161142.e-48"), ldexpf(9891056, -150));
+ EXPECT_EQ(ToFloat("25933168707.e-13"), ldexpf(11138211, -32));
+ EXPECT_EQ(ToFloat("596428896559.e20"), ldexpf(12333860, 82));
+
+
+ EXPECT_EQ(ToDouble("9.e-265"), ldexp(8168427841980010, -930));
+ EXPECT_EQ(ToDouble("85.e-037"), ldexp(6360455125664090, -169));
+ EXPECT_EQ(ToDouble("623.e100"), ldexp(6263531988747231, 289));
+ EXPECT_EQ(ToDouble("3571.e263"), ldexp(6234526311072170, 833));
+ EXPECT_EQ(ToDouble("81661.e153"), ldexp(6696636728760206, 472));
+ EXPECT_EQ(ToDouble("920657.e-023"), ldexp(5975405561110124, -109));
+ EXPECT_EQ(ToDouble("4603285.e-024"), ldexp(5975405561110124, -110));
+ EXPECT_EQ(ToDouble("87575437.e-309"), ldexp(8452160731874668, -1053));
+ EXPECT_EQ(ToDouble("245540327.e122"), ldexp(4985336549131723, 381));
+ EXPECT_EQ(ToDouble("6138508175.e120"), ldexp(4985336549131723, 379));
+ EXPECT_EQ(ToDouble("83356057653.e193"), ldexp(5986732817132056, 625));
+ EXPECT_EQ(ToDouble("619534293513.e124"), ldexp(4798406992060657, 399));
+ EXPECT_EQ(ToDouble("2335141086879.e218"), ldexp(5419088166961646, 713));
+ EXPECT_EQ(ToDouble("36167929443327.e-159"), ldexp(8135819834632444, -536));
+ EXPECT_EQ(ToDouble("609610927149051.e-255"), ldexp(4576664294594737, -850));
+ EXPECT_EQ(ToDouble("3743626360493413.e-165"), ldexp(6898586531774201, -549));
+ EXPECT_EQ(ToDouble("94080055902682397.e-242"), ldexp(6273271706052298, -800));
+ EXPECT_EQ(ToDouble("899810892172646163.e283"), ldexp(7563892574477827, 947));
+ EXPECT_EQ(ToDouble("7120190517612959703.e120"), ldexp(5385467232557565, 409));
+ EXPECT_EQ(ToDouble("25188282901709339043.e-252"),
+ ldexp(5635662608542340, -825));
+ EXPECT_EQ(ToDouble("308984926168550152811.e-052"),
+ ldexp(5644774693823803, -157));
+ EXPECT_EQ(ToDouble("6372891218502368041059.e064"),
+ ldexp(4616868614322430, 233));
+
+ EXPECT_EQ(ToFloat("3.e-23"), ldexpf(9507380, -98));
+ EXPECT_EQ(ToFloat("57.e18"), ldexpf(12960300, 42));
+ EXPECT_EQ(ToFloat("789.e-35"), ldexpf(10739312, -130));
+ EXPECT_EQ(ToFloat("2539.e-18"), ldexpf(11990089, -72));
+ EXPECT_EQ(ToFloat("76173.e28"), ldexpf(9845130, 86));
+ EXPECT_EQ(ToFloat("887745.e-11"), ldexpf(9760860, -40));
+ EXPECT_EQ(ToFloat("5382571.e-37"), ldexpf(11447463, -124));
+ EXPECT_EQ(ToFloat("82381273.e-35"), ldexpf(8554961, -113));
+ EXPECT_EQ(ToFloat("750486563.e-38"), ldexpf(9975678, -120));
+ EXPECT_EQ(ToFloat("3752432815.e-39"), ldexpf(9975678, -121));
+ EXPECT_EQ(ToFloat("75224575729.e-45"), ldexpf(13105970, -137));
+ EXPECT_EQ(ToFloat("459926601011.e15"), ldexpf(12466336, 65));
+}
+
+// Common test logic for converting a std::string which lies exactly halfway between
+// two target floats.
+//
+// mantissa and exponent represent the precise value between two floating point
+// numbers, `expected_low` and `expected_high`. The floating point
+// representation to parse in `StrCat(mantissa, "e", exponent)`.
+//
+// This function checks that an input just slightly less than the exact value
+// is rounded down to `expected_low`, and an input just slightly greater than
+// the exact value is rounded up to `expected_high`.
+//
+// The exact value should round to `expected_half`, which must be either
+// `expected_low` or `expected_high`.
+template <typename FloatType>
+void TestHalfwayValue(const std::string& mantissa, int exponent,
+ FloatType expected_low, FloatType expected_high,
+ FloatType expected_half) {
+ std::string low_rep = mantissa;
+ low_rep[low_rep.size() - 1] -= 1;
+ absl::StrAppend(&low_rep, std::string(1000, '9'), "e", exponent);
+
+ FloatType actual_low = 0;
+ absl::from_chars(low_rep.data(), low_rep.data() + low_rep.size(), actual_low);
+ EXPECT_EQ(expected_low, actual_low);
+
+ std::string high_rep = absl::StrCat(mantissa, std::string(1000, '0'), "1e", exponent);
+ FloatType actual_high = 0;
+ absl::from_chars(high_rep.data(), high_rep.data() + high_rep.size(),
+ actual_high);
+ EXPECT_EQ(expected_high, actual_high);
+
+ std::string halfway_rep = absl::StrCat(mantissa, "e", exponent);
+ FloatType actual_half = 0;
+ absl::from_chars(halfway_rep.data(), halfway_rep.data() + halfway_rep.size(),
+ actual_half);
+ EXPECT_EQ(expected_half, actual_half);
+}
+
+TEST(FromChars, DoubleRounding) {
+ const double zero = 0.0;
+ const double first_subnormal = nextafter(zero, 1.0);
+ const double second_subnormal = nextafter(first_subnormal, 1.0);
+
+ const double first_normal = DBL_MIN;
+ const double last_subnormal = nextafter(first_normal, 0.0);
+ const double second_normal = nextafter(first_normal, 1.0);
+
+ const double last_normal = DBL_MAX;
+ const double penultimate_normal = nextafter(last_normal, 0.0);
+
+ // Various test cases for numbers between two representable floats. Each
+ // call to TestHalfwayValue tests a number just below and just above the
+ // halfway point, as well as the number exactly between them.
+
+ // Test between zero and first_subnormal. Round-to-even tie rounds down.
+ TestHalfwayValue(
+ "2."
+ "470328229206232720882843964341106861825299013071623822127928412503377536"
+ "351043759326499181808179961898982823477228588654633283551779698981993873"
+ "980053909390631503565951557022639229085839244910518443593180284993653615"
+ "250031937045767824921936562366986365848075700158576926990370631192827955"
+ "855133292783433840935197801553124659726357957462276646527282722005637400"
+ "648549997709659947045402082816622623785739345073633900796776193057750674"
+ "017632467360096895134053553745851666113422376667860416215968046191446729"
+ "184030053005753084904876539171138659164623952491262365388187963623937328"
+ "042389101867234849766823508986338858792562830275599565752445550725518931"
+ "369083625477918694866799496832404970582102851318545139621383772282614543"
+ "7693412532098591327667236328125",
+ -324, zero, first_subnormal, zero);
+
+ // first_subnormal and second_subnormal. Round-to-even tie rounds up.
+ TestHalfwayValue(
+ "7."
+ "410984687618698162648531893023320585475897039214871466383785237510132609"
+ "053131277979497545424539885696948470431685765963899850655339096945981621"
+ "940161728171894510697854671067917687257517734731555330779540854980960845"
+ "750095811137303474765809687100959097544227100475730780971111893578483867"
+ "565399878350301522805593404659373979179073872386829939581848166016912201"
+ "945649993128979841136206248449867871357218035220901702390328579173252022"
+ "052897402080290685402160661237554998340267130003581248647904138574340187"
+ "552090159017259254714629617513415977493871857473787096164563890871811984"
+ "127167305601704549300470526959016576377688490826798697257336652176556794"
+ "107250876433756084600398490497214911746308553955635418864151316847843631"
+ "3080237596295773983001708984375",
+ -324, first_subnormal, second_subnormal, second_subnormal);
+
+ // last_subnormal and first_normal. Round-to-even tie rounds up.
+ TestHalfwayValue(
+ "2."
+ "225073858507201136057409796709131975934819546351645648023426109724822222"
+ "021076945516529523908135087914149158913039621106870086438694594645527657"
+ "207407820621743379988141063267329253552286881372149012981122451451889849"
+ "057222307285255133155755015914397476397983411801999323962548289017107081"
+ "850690630666655994938275772572015763062690663332647565300009245888316433"
+ "037779791869612049497390377829704905051080609940730262937128958950003583"
+ "799967207254304360284078895771796150945516748243471030702609144621572289"
+ "880258182545180325707018860872113128079512233426288368622321503775666622"
+ "503982534335974568884423900265498198385487948292206894721689831099698365"
+ "846814022854243330660339850886445804001034933970427567186443383770486037"
+ "86162277173854562306587467901408672332763671875",
+ -308, last_subnormal, first_normal, first_normal);
+
+ // first_normal and second_normal. Round-to-even tie rounds down.
+ TestHalfwayValue(
+ "2."
+ "225073858507201630123055637955676152503612414573018013083228724049586647"
+ "606759446192036794116886953213985520549032000903434781884412325572184367"
+ "563347617020518175998922941393629966742598285899994830148971433555578567"
+ "693279306015978183162142425067962460785295885199272493577688320732492479"
+ "924816869232247165964934329258783950102250973957579510571600738343645738"
+ "494324192997092179207389919761694314131497173265255020084997973676783743"
+ "155205818804439163810572367791175177756227497413804253387084478193655533"
+ "073867420834526162513029462022730109054820067654020201547112002028139700"
+ "141575259123440177362244273712468151750189745559978653234255886219611516"
+ "335924167958029604477064946470184777360934300451421683607013647479513962"
+ "13837722826145437693412532098591327667236328125",
+ -308, first_normal, second_normal, first_normal);
+
+ // penultimate_normal and last_normal. Round-to-even rounds down.
+ TestHalfwayValue(
+ "1."
+ "797693134862315608353258760581052985162070023416521662616611746258695532"
+ "672923265745300992879465492467506314903358770175220871059269879629062776"
+ "047355692132901909191523941804762171253349609463563872612866401980290377"
+ "995141836029815117562837277714038305214839639239356331336428021390916694"
+ "57927874464075218944",
+ 308, penultimate_normal, last_normal, penultimate_normal);
+}
+
+// Same test cases as DoubleRounding, now with new and improved Much Smaller
+// Precision!
+TEST(FromChars, FloatRounding) {
+ const float zero = 0.0;
+ const float first_subnormal = nextafterf(zero, 1.0);
+ const float second_subnormal = nextafterf(first_subnormal, 1.0);
+
+ const float first_normal = FLT_MIN;
+ const float last_subnormal = nextafterf(first_normal, 0.0);
+ const float second_normal = nextafterf(first_normal, 1.0);
+
+ const float last_normal = FLT_MAX;
+ const float penultimate_normal = nextafterf(last_normal, 0.0);
+
+ // Test between zero and first_subnormal. Round-to-even tie rounds down.
+ TestHalfwayValue(
+ "7."
+ "006492321624085354618647916449580656401309709382578858785341419448955413"
+ "42930300743319094181060791015625",
+ -46, zero, first_subnormal, zero);
+
+ // first_subnormal and second_subnormal. Round-to-even tie rounds up.
+ TestHalfwayValue(
+ "2."
+ "101947696487225606385594374934874196920392912814773657635602425834686624"
+ "028790902229957282543182373046875",
+ -45, first_subnormal, second_subnormal, second_subnormal);
+
+ // last_subnormal and first_normal. Round-to-even tie rounds up.
+ TestHalfwayValue(
+ "1."
+ "175494280757364291727882991035766513322858992758990427682963118425003064"
+ "9651730385585324256680905818939208984375",
+ -38, last_subnormal, first_normal, first_normal);
+
+ // first_normal and second_normal. Round-to-even tie rounds down.
+ TestHalfwayValue(
+ "1."
+ "175494420887210724209590083408724842314472120785184615334540294131831453"
+ "9442813071445925743319094181060791015625",
+ -38, first_normal, second_normal, first_normal);
+
+ // penultimate_normal and last_normal. Round-to-even rounds down.
+ TestHalfwayValue("3.40282336497324057985868971510891282432", 38,
+ penultimate_normal, last_normal, penultimate_normal);
+}
+
+TEST(FromChars, Underflow) {
+ // Check that underflow is handled correctly, according to the specification
+ // in DR 3081.
+ double d;
+ float f;
+ absl::from_chars_result result;
+
+ std::string negative_underflow = "-1e-1000";
+ const char* begin = negative_underflow.data();
+ const char* end = begin + negative_underflow.size();
+ d = 100.0;
+ result = absl::from_chars(begin, end, d);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_TRUE(std::signbit(d)); // negative
+ EXPECT_GE(d, -std::numeric_limits<double>::min());
+ f = 100.0;
+ result = absl::from_chars(begin, end, f);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_TRUE(std::signbit(f)); // negative
+ EXPECT_GE(f, -std::numeric_limits<float>::min());
+
+ std::string positive_underflow = "1e-1000";
+ begin = positive_underflow.data();
+ end = begin + positive_underflow.size();
+ d = -100.0;
+ result = absl::from_chars(begin, end, d);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_FALSE(std::signbit(d)); // positive
+ EXPECT_LE(d, std::numeric_limits<double>::min());
+ f = -100.0;
+ result = absl::from_chars(begin, end, f);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_FALSE(std::signbit(f)); // positive
+ EXPECT_LE(f, std::numeric_limits<float>::min());
+}
+
+TEST(FromChars, Overflow) {
+ // Check that overflow is handled correctly, according to the specification
+ // in DR 3081.
+ double d;
+ float f;
+ absl::from_chars_result result;
+
+ std::string negative_overflow = "-1e1000";
+ const char* begin = negative_overflow.data();
+ const char* end = begin + negative_overflow.size();
+ d = 100.0;
+ result = absl::from_chars(begin, end, d);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_TRUE(std::signbit(d)); // negative
+ EXPECT_EQ(d, -std::numeric_limits<double>::max());
+ f = 100.0;
+ result = absl::from_chars(begin, end, f);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_TRUE(std::signbit(f)); // negative
+ EXPECT_EQ(f, -std::numeric_limits<float>::max());
+
+ std::string positive_overflow = "1e1000";
+ begin = positive_overflow.data();
+ end = begin + positive_overflow.size();
+ d = -100.0;
+ result = absl::from_chars(begin, end, d);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_FALSE(std::signbit(d)); // positive
+ EXPECT_EQ(d, std::numeric_limits<double>::max());
+ f = -100.0;
+ result = absl::from_chars(begin, end, f);
+ EXPECT_EQ(result.ptr, end);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_FALSE(std::signbit(f)); // positive
+ EXPECT_EQ(f, std::numeric_limits<float>::max());
+}
+
+TEST(FromChars, ReturnValuePtr) {
+ // Check that `ptr` points one past the number scanned, even if that number
+ // is not representable.
+ double d;
+ absl::from_chars_result result;
+
+ std::string normal = "3.14@#$%@#$%";
+ result = absl::from_chars(normal.data(), normal.data() + normal.size(), d);
+ EXPECT_EQ(result.ec, std::errc());
+ EXPECT_EQ(result.ptr - normal.data(), 4);
+
+ std::string overflow = "1e1000@#$%@#$%";
+ result = absl::from_chars(overflow.data(),
+ overflow.data() + overflow.size(), d);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_EQ(result.ptr - overflow.data(), 6);
+
+ std::string garbage = "#$%@#$%";
+ result = absl::from_chars(garbage.data(),
+ garbage.data() + garbage.size(), d);
+ EXPECT_EQ(result.ec, std::errc::invalid_argument);
+ EXPECT_EQ(result.ptr - garbage.data(), 0);
+}
+
+// Check for a wide range of inputs that strtod() and absl::from_chars() exactly
+// agree on the conversion amount.
+//
+// This test assumes the platform's strtod() uses perfect round_to_nearest
+// rounding.
+TEST(FromChars, TestVersusStrtod) {
+ for (int mantissa = 1000000; mantissa <= 9999999; mantissa += 501) {
+ for (int exponent = -300; exponent < 300; ++exponent) {
+ std::string candidate = absl::StrCat(mantissa, "e", exponent);
+ double strtod_value = strtod(candidate.c_str(), nullptr);
+ double absl_value = 0;
+ absl::from_chars(candidate.data(), candidate.data() + candidate.size(),
+ absl_value);
+ ASSERT_EQ(strtod_value, absl_value) << candidate;
+ }
+ }
+}
+
+// Check for a wide range of inputs that strtof() and absl::from_chars() exactly
+// agree on the conversion amount.
+//
+// This test assumes the platform's strtof() uses perfect round_to_nearest
+// rounding.
+TEST(FromChars, TestVersusStrtof) {
+ for (int mantissa = 1000000; mantissa <= 9999999; mantissa += 501) {
+ for (int exponent = -43; exponent < 32; ++exponent) {
+ std::string candidate = absl::StrCat(mantissa, "e", exponent);
+ float strtod_value = strtof(candidate.c_str(), nullptr);
+ float absl_value = 0;
+ absl::from_chars(candidate.data(), candidate.data() + candidate.size(),
+ absl_value);
+ ASSERT_EQ(strtod_value, absl_value) << candidate;
+ }
+ }
+}
+
+// Tests if two floating point values have identical bit layouts. (EXPECT_EQ
+// is not suitable for NaN testing, since NaNs are never equal.)
+template <typename Float>
+bool Identical(Float a, Float b) {
+ return 0 == memcmp(&a, &b, sizeof(Float));
+}
+
+// Check that NaNs are parsed correctly. The spec requires that
+// std::from_chars on "NaN(123abc)" return the same value as std::nan("123abc").
+// How such an n-char-sequence affects the generated NaN is unspecified, so we
+// just test for symmetry with std::nan and strtod here.
+//
+// (In Linux, this parses the value as a number and stuffs that number into the
+// free bits of a quiet NaN.)
+TEST(FromChars, NaNDoubles) {
+ for (std::string n_char_sequence :
+ {"", "1", "2", "3", "fff", "FFF", "200000", "400000", "4000000000000",
+ "8000000000000", "abc123", "legal_but_unexpected",
+ "99999999999999999999999", "_"}) {
+ std::string input = absl::StrCat("nan(", n_char_sequence, ")");
+ SCOPED_TRACE(input);
+ double from_chars_double;
+ absl::from_chars(input.data(), input.data() + input.size(),
+ from_chars_double);
+ double std_nan_double = std::nan(n_char_sequence.c_str());
+ EXPECT_TRUE(Identical(from_chars_double, std_nan_double));
+
+ // Also check that we match strtod()'s behavior. This test assumes that the
+ // platform has a compliant strtod().
+#if ABSL_STRTOD_HANDLES_NAN_CORRECTLY
+ double strtod_double = strtod(input.c_str(), nullptr);
+ EXPECT_TRUE(Identical(from_chars_double, strtod_double));
+#endif // ABSL_STRTOD_HANDLES_NAN_CORRECTLY
+
+ // Check that we can parse a negative NaN
+ std::string negative_input = "-" + input;
+ double negative_from_chars_double;
+ absl::from_chars(negative_input.data(),
+ negative_input.data() + negative_input.size(),
+ negative_from_chars_double);
+ EXPECT_TRUE(std::signbit(negative_from_chars_double));
+ EXPECT_FALSE(Identical(negative_from_chars_double, from_chars_double));
+ from_chars_double = std::copysign(from_chars_double, -1.0);
+ EXPECT_TRUE(Identical(negative_from_chars_double, from_chars_double));
+ }
+}
+
+TEST(FromChars, NaNFloats) {
+ for (std::string n_char_sequence :
+ {"", "1", "2", "3", "fff", "FFF", "200000", "400000", "4000000000000",
+ "8000000000000", "abc123", "legal_but_unexpected",
+ "99999999999999999999999", "_"}) {
+ std::string input = absl::StrCat("nan(", n_char_sequence, ")");
+ SCOPED_TRACE(input);
+ float from_chars_float;
+ absl::from_chars(input.data(), input.data() + input.size(),
+ from_chars_float);
+ float std_nan_float = std::nanf(n_char_sequence.c_str());
+ EXPECT_TRUE(Identical(from_chars_float, std_nan_float));
+
+ // Also check that we match strtof()'s behavior. This test assumes that the
+ // platform has a compliant strtof().
+#if ABSL_STRTOD_HANDLES_NAN_CORRECTLY
+ float strtof_float = strtof(input.c_str(), nullptr);
+ EXPECT_TRUE(Identical(from_chars_float, strtof_float));
+#endif // ABSL_STRTOD_HANDLES_NAN_CORRECTLY
+
+ // Check that we can parse a negative NaN
+ std::string negative_input = "-" + input;
+ float negative_from_chars_float;
+ absl::from_chars(negative_input.data(),
+ negative_input.data() + negative_input.size(),
+ negative_from_chars_float);
+ EXPECT_TRUE(std::signbit(negative_from_chars_float));
+ EXPECT_FALSE(Identical(negative_from_chars_float, from_chars_float));
+ from_chars_float = std::copysign(from_chars_float, -1.0);
+ EXPECT_TRUE(Identical(negative_from_chars_float, from_chars_float));
+ }
+}
+
+// Returns an integer larger than step. The values grow exponentially.
+int NextStep(int step) {
+ return step + (step >> 2) + 1;
+}
+
+// Test a conversion on a family of input strings, checking that the calculation
+// is correct for in-bounds values, and that overflow and underflow are done
+// correctly for out-of-bounds values.
+//
+// input_generator maps from an integer index to a std::string to test.
+// expected_generator maps from an integer index to an expected Float value.
+// from_chars conversion of input_generator(i) should result in
+// expected_generator(i).
+//
+// lower_bound and upper_bound denote the smallest and largest values for which
+// the conversion is expected to succeed.
+template <typename Float>
+void TestOverflowAndUnderflow(
+ const std::function<std::string(int)>& input_generator,
+ const std::function<Float(int)>& expected_generator, int lower_bound,
+ int upper_bound) {
+ // test legal values near lower_bound
+ int index, step;
+ for (index = lower_bound, step = 1; index < upper_bound;
+ index += step, step = NextStep(step)) {
+ std::string input = input_generator(index);
+ SCOPED_TRACE(input);
+ Float expected = expected_generator(index);
+ Float actual;
+ auto result =
+ absl::from_chars(input.data(), input.data() + input.size(), actual);
+ EXPECT_EQ(result.ec, std::errc());
+ EXPECT_EQ(expected, actual);
+ }
+ // test legal values near upper_bound
+ for (index = upper_bound, step = 1; index > lower_bound;
+ index -= step, step = NextStep(step)) {
+ std::string input = input_generator(index);
+ SCOPED_TRACE(input);
+ Float expected = expected_generator(index);
+ Float actual;
+ auto result =
+ absl::from_chars(input.data(), input.data() + input.size(), actual);
+ EXPECT_EQ(result.ec, std::errc());
+ EXPECT_EQ(expected, actual);
+ }
+ // Test underflow values below lower_bound
+ for (index = lower_bound - 1, step = 1; index > -1000000;
+ index -= step, step = NextStep(step)) {
+ std::string input = input_generator(index);
+ SCOPED_TRACE(input);
+ Float actual;
+ auto result =
+ absl::from_chars(input.data(), input.data() + input.size(), actual);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_LT(actual, 1.0); // check for underflow
+ }
+ // Test overflow values above upper_bound
+ for (index = upper_bound + 1, step = 1; index < 1000000;
+ index += step, step = NextStep(step)) {
+ std::string input = input_generator(index);
+ SCOPED_TRACE(input);
+ Float actual;
+ auto result =
+ absl::from_chars(input.data(), input.data() + input.size(), actual);
+ EXPECT_EQ(result.ec, std::errc::result_out_of_range);
+ EXPECT_GT(actual, 1.0); // check for overflow
+ }
+}
+
+// Check that overflow and underflow are caught correctly for hex doubles.
+//
+// The largest representable double is 0x1.fffffffffffffp+1023, and the
+// smallest representable subnormal is 0x0.0000000000001p-1022, which equals
+// 0x1p-1074. Therefore 1023 and -1074 are the limits of acceptable exponents
+// in this test.
+TEST(FromChars, HexdecimalDoubleLimits) {
+ auto input_gen = [](int index) { return absl::StrCat("0x1.0p", index); };
+ auto expected_gen = [](int index) { return std::ldexp(1.0, index); };
+ TestOverflowAndUnderflow<double>(input_gen, expected_gen, -1074, 1023);
+}
+
+// Check that overflow and underflow are caught correctly for hex floats.
+//
+// The largest representable float is 0x1.fffffep+127, and the smallest
+// representable subnormal is 0x0.000002p-126, which equals 0x1p-149.
+// Therefore 127 and -149 are the limits of acceptable exponents in this test.
+TEST(FromChars, HexdecimalFloatLimits) {
+ auto input_gen = [](int index) { return absl::StrCat("0x1.0p", index); };
+ auto expected_gen = [](int index) { return std::ldexp(1.0f, index); };
+ TestOverflowAndUnderflow<float>(input_gen, expected_gen, -149, 127);
+}
+
+// Check that overflow and underflow are caught correctly for decimal doubles.
+//
+// The largest representable double is about 1.8e308, and the smallest
+// representable subnormal is about 5e-324. '1e-324' therefore rounds away from
+// the smallest representable positive value. -323 and 308 are the limits of
+// acceptable exponents in this test.
+TEST(FromChars, DecimalDoubleLimits) {
+ auto input_gen = [](int index) { return absl::StrCat("1.0e", index); };
+ auto expected_gen = [](int index) { return std::pow(10.0, index); };
+ TestOverflowAndUnderflow<double>(input_gen, expected_gen, -323, 308);
+}
+
+// Check that overflow and underflow are caught correctly for decimal floats.
+//
+// The largest representable float is about 3.4e38, and the smallest
+// representable subnormal is about 1.45e-45. '1e-45' therefore rounds towards
+// the smallest representable positive value. -45 and 38 are the limits of
+// acceptable exponents in this test.
+TEST(FromChars, DecimalFloatLimits) {
+ auto input_gen = [](int index) { return absl::StrCat("1.0e", index); };
+ auto expected_gen = [](int index) { return std::pow(10.0, index); };
+ TestOverflowAndUnderflow<float>(input_gen, expected_gen, -45, 38);
+}
+
+} // namespace
diff --git a/absl/strings/internal/charconv_bigint.cc b/absl/strings/internal/charconv_bigint.cc
new file mode 100644
index 00000000..3e7296e7
--- /dev/null
+++ b/absl/strings/internal/charconv_bigint.cc
@@ -0,0 +1,357 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/charconv_bigint.h"
+
+#include <algorithm>
+#include <cassert>
+#include <string>
+
+namespace absl {
+namespace strings_internal {
+
+namespace {
+
+// Table containing some large powers of 5, for fast computation.
+
+// Constant step size for entries in the kLargePowersOfFive table. Each entry
+// is larger than the previous entry by a factor of 5**kLargePowerOfFiveStep
+// (or 5**27).
+//
+// In other words, the Nth entry in the table is 5**(27*N).
+//
+// 5**27 is the largest power of 5 that fits in 64 bits.
+constexpr int kLargePowerOfFiveStep = 27;
+
+// The largest legal index into the kLargePowersOfFive table.
+//
+// In other words, the largest precomputed power of 5 is 5**(27*20).
+constexpr int kLargestPowerOfFiveIndex = 20;
+
+// Table of powers of (5**27), up to (5**27)**20 == 5**540.
+//
+// Used to generate large powers of 5 while limiting the number of repeated
+// multiplications required.
+//
+// clang-format off
+const uint32_t kLargePowersOfFive[] = {
+// 5**27 (i=1), start=0, end=2
+ 0xfa10079dU, 0x6765c793U,
+// 5**54 (i=2), start=2, end=6
+ 0x97d9f649U, 0x6664242dU, 0x29939b14U, 0x29c30f10U,
+// 5**81 (i=3), start=6, end=12
+ 0xc4f809c5U, 0x7bf3f22aU, 0x67bdae34U, 0xad340517U, 0x369d1b5fU, 0x10de1593U,
+// 5**108 (i=4), start=12, end=20
+ 0x92b260d1U, 0x9efff7c7U, 0x81de0ec6U, 0xaeba5d56U, 0x410664a4U, 0x4f40737aU,
+ 0x20d3846fU, 0x06d00f73U,
+// 5**135 (i=5), start=20, end=30
+ 0xff1b172dU, 0x13a1d71cU, 0xefa07617U, 0x7f682d3dU, 0xff8c90c0U, 0x3f0131e7U,
+ 0x3fdcb9feU, 0x917b0177U, 0x16c407a7U, 0x02c06b9dU,
+// 5**162 (i=6), start=30, end=42
+ 0x960f7199U, 0x056667ecU, 0xe07aefd8U, 0x80f2b9ccU, 0x8273f5e3U, 0xeb9a214aU,
+ 0x40b38005U, 0x0e477ad4U, 0x277d08e6U, 0xfa28b11eU, 0xd3f7d784U, 0x011c835bU,
+// 5**189 (i=7), start=42, end=56
+ 0xf723d9d5U, 0x3282d3f3U, 0xe00857d1U, 0x69659d25U, 0x2cf117cfU, 0x24da6d07U,
+ 0x954d1417U, 0x3e5d8cedU, 0x7a8bb766U, 0xfd785ae6U, 0x645436d2U, 0x40c78b34U,
+ 0x94151217U, 0x0072e9f7U,
+// 5**216 (i=8), start=56, end=72
+ 0x2b416aa1U, 0x7893c5a7U, 0xe37dc6d4U, 0x2bad2beaU, 0xf0fc846cU, 0x7575ae4bU,
+ 0x62587b14U, 0x83b67a34U, 0x02110cdbU, 0xf7992f55U, 0x00deb022U, 0xa4a23becU,
+ 0x8af5c5cdU, 0xb85b654fU, 0x818df38bU, 0x002e69d2U,
+// 5**243 (i=9), start=72, end=90
+ 0x3518cbbdU, 0x20b0c15fU, 0x38756c2fU, 0xfb5dc3ddU, 0x22ad2d94U, 0xbf35a952U,
+ 0xa699192aU, 0x9a613326U, 0xad2a9cedU, 0xd7f48968U, 0xe87dfb54U, 0xc8f05db6U,
+ 0x5ef67531U, 0x31c1ab49U, 0xe202ac9fU, 0x9b2957b5U, 0xa143f6d3U, 0x0012bf07U,
+// 5**270 (i=10), start=90, end=110
+ 0x8b971de9U, 0x21aba2e1U, 0x63944362U, 0x57172336U, 0xd9544225U, 0xfb534166U,
+ 0x08c563eeU, 0x14640ee2U, 0x24e40d31U, 0x02b06537U, 0x03887f14U, 0x0285e533U,
+ 0xb744ef26U, 0x8be3a6c4U, 0x266979b4U, 0x6761ece2U, 0xd9cb39e4U, 0xe67de319U,
+ 0x0d39e796U, 0x00079250U,
+// 5**297 (i=11), start=110, end=132
+ 0x260eb6e5U, 0xf414a796U, 0xee1a7491U, 0xdb9368ebU, 0xf50c105bU, 0x59157750U,
+ 0x9ed2fb5cU, 0xf6e56d8bU, 0xeaee8d23U, 0x0f319f75U, 0x2aa134d6U, 0xac2908e9U,
+ 0xd4413298U, 0x02f02a55U, 0x989d5a7aU, 0x70dde184U, 0xba8040a7U, 0x03200981U,
+ 0xbe03b11cU, 0x3c1c2a18U, 0xd60427a1U, 0x00030ee0U,
+// 5**324 (i=12), start=132, end=156
+ 0xce566d71U, 0xf1c4aa25U, 0x4e93ca53U, 0xa72283d0U, 0x551a73eaU, 0x3d0538e2U,
+ 0x8da4303fU, 0x6a58de60U, 0x0e660221U, 0x49cf61a6U, 0x8d058fc1U, 0xb9d1a14cU,
+ 0x4bab157dU, 0xc85c6932U, 0x518c8b9eU, 0x9b92b8d0U, 0x0d8a0e21U, 0xbd855df9U,
+ 0xb3ea59a1U, 0x8da29289U, 0x4584d506U, 0x3752d80fU, 0xb72569c6U, 0x00013c33U,
+// 5**351 (i=13), start=156, end=182
+ 0x190f354dU, 0x83695cfeU, 0xe5a4d0c7U, 0xb60fb7e8U, 0xee5bbcc4U, 0xb922054cU,
+ 0xbb4f0d85U, 0x48394028U, 0x1d8957dbU, 0x0d7edb14U, 0x4ecc7587U, 0x505e9e02U,
+ 0x4c87f36bU, 0x99e66bd6U, 0x44b9ed35U, 0x753037d4U, 0xe5fe5f27U, 0x2742c203U,
+ 0x13b2ed2bU, 0xdc525d2cU, 0xe6fde59aU, 0x77ffb18fU, 0x13c5752cU, 0x08a84bccU,
+ 0x859a4940U, 0x00007fb6U,
+// 5**378 (i=14), start=182, end=210
+ 0x4f98cb39U, 0xa60edbbcU, 0x83b5872eU, 0xa501acffU, 0x9cc76f78U, 0xbadd4c73U,
+ 0x43e989faU, 0xca7acf80U, 0x2e0c824fU, 0xb19f4ffcU, 0x092fd81cU, 0xe4eb645bU,
+ 0xa1ff84c2U, 0x8a5a83baU, 0xa8a1fae9U, 0x1db43609U, 0xb0fed50bU, 0x0dd7d2bdU,
+ 0x7d7accd8U, 0x91fa640fU, 0x37dcc6c5U, 0x1c417fd5U, 0xe4d462adU, 0xe8a43399U,
+ 0x131bf9a5U, 0x8df54d29U, 0x36547dc1U, 0x00003395U,
+// 5**405 (i=15), start=210, end=240
+ 0x5bd330f5U, 0x77d21967U, 0x1ac481b7U, 0x6be2f7ceU, 0x7f4792a9U, 0xe84c2c52U,
+ 0x84592228U, 0x9dcaf829U, 0xdab44ce1U, 0x3d0c311bU, 0x532e297dU, 0x4704e8b4U,
+ 0x9cdc32beU, 0x41e64d9dU, 0x7717bea1U, 0xa824c00dU, 0x08f50b27U, 0x0f198d77U,
+ 0x49bbfdf0U, 0x025c6c69U, 0xd4e55cd3U, 0xf083602bU, 0xb9f0fecdU, 0xc0864aeaU,
+ 0x9cb98681U, 0xaaf620e9U, 0xacb6df30U, 0x4faafe66U, 0x8af13c3bU, 0x000014d5U,
+// 5**432 (i=16), start=240, end=272
+ 0x682bb941U, 0x89a9f297U, 0xcba75d7bU, 0x404217b1U, 0xb4e519e9U, 0xa1bc162bU,
+ 0xf7f5910aU, 0x98715af5U, 0x2ff53e57U, 0xe3ef118cU, 0x490c4543U, 0xbc9b1734U,
+ 0x2affbe4dU, 0x4cedcb4cU, 0xfb14e99eU, 0x35e34212U, 0xece39c24U, 0x07673ab3U,
+ 0xe73115ddU, 0xd15d38e7U, 0x093eed3bU, 0xf8e7eac5U, 0x78a8cc80U, 0x25227aacU,
+ 0x3f590551U, 0x413da1cbU, 0xdf643a55U, 0xab65ad44U, 0xd70b23d7U, 0xc672cd76U,
+ 0x3364ea62U, 0x0000086aU,
+// 5**459 (i=17), start=272, end=306
+ 0x22f163ddU, 0x23cf07acU, 0xbe2af6c2U, 0xf412f6f6U, 0xc3ff541eU, 0x6eeaf7deU,
+ 0xa47047e0U, 0x408cda92U, 0x0f0eeb08U, 0x56deba9dU, 0xcfc6b090U, 0x8bbbdf04U,
+ 0x3933cdb3U, 0x9e7bb67dU, 0x9f297035U, 0x38946244U, 0xee1d37bbU, 0xde898174U,
+ 0x63f3559dU, 0x705b72fbU, 0x138d27d9U, 0xf8603a78U, 0x735eec44U, 0xe30987d5U,
+ 0xc6d38070U, 0x9cfe548eU, 0x9ff01422U, 0x7c564aa8U, 0x91cc60baU, 0xcbc3565dU,
+ 0x7550a50bU, 0x6909aeadU, 0x13234c45U, 0x00000366U,
+// 5**486 (i=18), start=306, end=342
+ 0x17954989U, 0x3a7d7709U, 0x98042de5U, 0xa9011443U, 0x45e723c2U, 0x269ffd6fU,
+ 0x58852a46U, 0xaaa1042aU, 0x2eee8153U, 0xb2b6c39eU, 0xaf845b65U, 0xf6c365d7U,
+ 0xe4cffb2bU, 0xc840e90cU, 0xabea8abbU, 0x5c58f8d2U, 0x5c19fa3aU, 0x4670910aU,
+ 0x4449f21cU, 0xefa645b3U, 0xcc427decU, 0x083c3d73U, 0x467cb413U, 0x6fe10ae4U,
+ 0x3caffc72U, 0x9f8da55eU, 0x5e5c8ea7U, 0x490594bbU, 0xf0871b0bU, 0xdd89816cU,
+ 0x8e931df8U, 0xe85ce1c9U, 0xcca090a5U, 0x575fa16bU, 0x6b9f106cU, 0x0000015fU,
+// 5**513 (i=19), start=342, end=380
+ 0xee20d805U, 0x57bc3c07U, 0xcdea624eU, 0xd3f0f52dU, 0x9924b4f4U, 0xcf968640U,
+ 0x61d41962U, 0xe87fb464U, 0xeaaf51c7U, 0x564c8b60U, 0xccda4028U, 0x529428bbU,
+ 0x313a1fa8U, 0x96bd0f94U, 0x7a82ebaaU, 0xad99e7e9U, 0xf2668cd4U, 0xbe33a45eU,
+ 0xfd0db669U, 0x87ee369fU, 0xd3ec20edU, 0x9c4d7db7U, 0xdedcf0d8U, 0x7cd2ca64U,
+ 0xe25a6577U, 0x61003fd4U, 0xe56f54ccU, 0x10b7c748U, 0x40526e5eU, 0x7300ae87U,
+ 0x5c439261U, 0x2c0ff469U, 0xbf723f12U, 0xb2379b61U, 0xbf59b4f5U, 0xc91b1c3fU,
+ 0xf0046d27U, 0x0000008dU,
+// 5**540 (i=20), start=380, end=420
+ 0x525c9e11U, 0xf4e0eb41U, 0xebb2895dU, 0x5da512f9U, 0x7d9b29d4U, 0x452f4edcU,
+ 0x0b90bc37U, 0x341777cbU, 0x63d269afU, 0x1da77929U, 0x0a5c1826U, 0x77991898U,
+ 0x5aeddf86U, 0xf853a877U, 0x538c31ccU, 0xe84896daU, 0xb7a0010bU, 0x17ef4de5U,
+ 0xa52a2adeU, 0x029fd81cU, 0x987ce701U, 0x27fefd77U, 0xdb46c66fU, 0x5d301900U,
+ 0x496998c0U, 0xbb6598b9U, 0x5eebb607U, 0xe547354aU, 0xdf4a2f7eU, 0xf06c4955U,
+ 0x96242ffaU, 0x1775fb27U, 0xbecc58ceU, 0xebf2a53bU, 0x3eaad82aU, 0xf41137baU,
+ 0x573e6fbaU, 0xfb4866b8U, 0x54002148U, 0x00000039U,
+};
+// clang-format on
+
+// Returns a pointer to the big integer data for (5**27)**i. i must be
+// between 1 and 20, inclusive.
+const uint32_t* LargePowerOfFiveData(int i) {
+ return kLargePowersOfFive + i * (i - 1);
+}
+
+// Returns the size of the big integer data for (5**27)**i, in words. i must be
+// between 1 and 20, inclusive.
+int LargePowerOfFiveSize(int i) { return 2 * i; }
+} // namespace
+
+const uint32_t kFiveToNth[14] = {
+ 1, 5, 25, 125, 625, 3125, 15625,
+ 78125, 390625, 1953125, 9765625, 48828125, 244140625, 1220703125,
+};
+
+const uint32_t kTenToNth[10] = {
+ 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000,
+};
+
+template <int max_words>
+int BigUnsigned<max_words>::ReadFloatMantissa(const ParsedFloat& fp,
+ int significant_digits) {
+ SetToZero();
+ assert(fp.type == FloatType::kNumber);
+
+ if (fp.subrange_begin == nullptr) {
+ // We already exactly parsed the mantissa, so no more work is necessary.
+ words_[0] = fp.mantissa & 0xffffffffu;
+ words_[1] = fp.mantissa >> 32;
+ if (words_[1]) {
+ size_ = 2;
+ } else if (words_[0]) {
+ size_ = 1;
+ }
+ return fp.exponent;
+ }
+ int exponent_adjust =
+ ReadDigits(fp.subrange_begin, fp.subrange_end, significant_digits);
+ return fp.literal_exponent + exponent_adjust;
+}
+
+template <int max_words>
+int BigUnsigned<max_words>::ReadDigits(const char* begin, const char* end,
+ int significant_digits) {
+ assert(significant_digits <= Digits10() + 1);
+ SetToZero();
+
+ bool after_decimal_point = false;
+ // Discard any leading zeroes before the decimal point
+ while (begin < end && *begin == '0') {
+ ++begin;
+ }
+ int dropped_digits = 0;
+ // Discard any trailing zeroes. These may or may not be after the decimal
+ // point.
+ while (begin < end && *std::prev(end) == '0') {
+ --end;
+ ++dropped_digits;
+ }
+ if (begin < end && *std::prev(end) == '.') {
+ // If the std::string ends in '.', either before or after dropping zeroes, then
+ // drop the decimal point and look for more digits to drop.
+ dropped_digits = 0;
+ --end;
+ while (begin < end && *std::prev(end) == '0') {
+ --end;
+ ++dropped_digits;
+ }
+ } else if (dropped_digits) {
+ // We dropped digits, and aren't sure if they're before or after the decimal
+ // point. Figure that out now.
+ const char* dp = std::find(begin, end, '.');
+ if (dp != end) {
+ // The dropped trailing digits were after the decimal point, so don't
+ // count them.
+ dropped_digits = 0;
+ }
+ }
+ // Any non-fraction digits we dropped need to be accounted for in our exponent
+ // adjustment.
+ int exponent_adjust = dropped_digits;
+
+ uint32_t queued = 0;
+ int digits_queued = 0;
+ for (; begin != end && significant_digits > 0; ++begin) {
+ if (*begin == '.') {
+ after_decimal_point = true;
+ continue;
+ }
+ if (after_decimal_point) {
+ // For each fractional digit we emit in our parsed integer, adjust our
+ // decimal exponent to compensate.
+ --exponent_adjust;
+ }
+ int digit = (*begin - '0');
+ --significant_digits;
+ if (significant_digits == 0 && std::next(begin) != end &&
+ (digit == 0 || digit == 5)) {
+ // If this is the very last significant digit, but insignificant digits
+ // remain, we know that the last of those remaining significant digits is
+ // nonzero. (If it wasn't, we would have stripped it before we got here.)
+ // So if this final digit is a 0 or 5, adjust it upward by 1.
+ //
+ // This adjustment is what allows incredibly large mantissas ending in
+ // 500000...000000000001 to correctly round up, rather than to nearest.
+ ++digit;
+ }
+ queued = 10 * queued + digit;
+ ++digits_queued;
+ if (digits_queued == kMaxSmallPowerOfTen) {
+ MultiplyBy(kTenToNth[kMaxSmallPowerOfTen]);
+ AddWithCarry(0, queued);
+ queued = digits_queued = 0;
+ }
+ }
+ // Encode any remaining digits.
+ if (digits_queued) {
+ MultiplyBy(kTenToNth[digits_queued]);
+ AddWithCarry(0, queued);
+ }
+
+ // If any insignificant digits remain, we will drop them. But if we have not
+ // yet read the decimal point, then we have to adjust the exponent to account
+ // for the dropped digits.
+ if (begin < end && !after_decimal_point) {
+ // This call to std::find will result in a pointer either to the decimal
+ // point, or to the end of our buffer if there was none.
+ //
+ // Either way, [begin, decimal_point) will contain the set of dropped digits
+ // that require an exponent adjustment.
+ const char* decimal_point = std::find(begin, end, '.');
+ exponent_adjust += (decimal_point - begin);
+ }
+ return exponent_adjust;
+}
+
+template <int max_words>
+/* static */ BigUnsigned<max_words> BigUnsigned<max_words>::FiveToTheNth(
+ int n) {
+ BigUnsigned answer(1u);
+
+ // Seed from the table of large powers, if possible.
+ bool first_pass = true;
+ while (n >= kLargePowerOfFiveStep) {
+ int big_power =
+ std::min(n / kLargePowerOfFiveStep, kLargestPowerOfFiveIndex);
+ if (first_pass) {
+ // just copy, rather than multiplying by 1
+ std::copy(
+ LargePowerOfFiveData(big_power),
+ LargePowerOfFiveData(big_power) + LargePowerOfFiveSize(big_power),
+ answer.words_);
+ answer.size_ = LargePowerOfFiveSize(big_power);
+ first_pass = false;
+ } else {
+ answer.MultiplyBy(LargePowerOfFiveSize(big_power),
+ LargePowerOfFiveData(big_power));
+ }
+ n -= kLargePowerOfFiveStep * big_power;
+ }
+ answer.MultiplyByFiveToTheNth(n);
+ return answer;
+}
+
+template <int max_words>
+void BigUnsigned<max_words>::MultiplyStep(int original_size,
+ const uint32_t* other_words,
+ int other_size, int step) {
+ int this_i = std::min(original_size - 1, step);
+ int other_i = step - this_i;
+
+ uint64_t this_word = 0;
+ uint64_t carry = 0;
+ for (; this_i >= 0 && other_i < other_size; --this_i, ++other_i) {
+ uint64_t product = words_[this_i];
+ product *= other_words[other_i];
+ this_word += product;
+ carry += (this_word >> 32);
+ this_word &= 0xffffffff;
+ }
+ AddWithCarry(step + 1, carry);
+ words_[step] = this_word & 0xffffffff;
+ if (this_word > 0 && size_ <= step) {
+ size_ = step + 1;
+ }
+}
+
+template <int max_words>
+std::string BigUnsigned<max_words>::ToString() const {
+ BigUnsigned<max_words> copy = *this;
+ std::string result;
+ // Build result in reverse order
+ while (copy.size() > 0) {
+ int next_digit = copy.DivMod<10>();
+ result.push_back('0' + next_digit);
+ }
+ if (result.empty()) {
+ result.push_back('0');
+ }
+ std::reverse(result.begin(), result.end());
+ return result;
+}
+
+template class BigUnsigned<4>;
+template class BigUnsigned<84>;
+
+} // namespace strings_internal
+} // namespace absl
diff --git a/absl/strings/internal/charconv_bigint.h b/absl/strings/internal/charconv_bigint.h
new file mode 100644
index 00000000..aa70af2c
--- /dev/null
+++ b/absl/strings/internal/charconv_bigint.h
@@ -0,0 +1,426 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_CHARCONV_BIGINT_H_
+#define ABSL_STRINGS_INTERNAL_CHARCONV_BIGINT_H_
+
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <string>
+
+#include "absl/strings/ascii.h"
+#include "absl/strings/internal/charconv_parse.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+namespace strings_internal {
+
+// The largest power that 5 that can be raised to, and still fit in a uint32_t.
+constexpr int kMaxSmallPowerOfFive = 13;
+// The largest power that 10 that can be raised to, and still fit in a uint32_t.
+constexpr int kMaxSmallPowerOfTen = 9;
+
+extern const uint32_t kFiveToNth[kMaxSmallPowerOfFive + 1];
+extern const uint32_t kTenToNth[kMaxSmallPowerOfTen + 1];
+
+// Large, fixed-width unsigned integer.
+//
+// Exact rounding for decimal-to-binary floating point conversion requires very
+// large integer math, but a design goal of absl::from_chars is to avoid
+// allocating memory. The integer precision needed for decimal-to-binary
+// conversions is large but bounded, so a huge fixed-width integer class
+// suffices.
+//
+// This is an intentionally limited big integer class. Only needed operations
+// are implemented. All storage lives in an array data member, and all
+// arithmetic is done in-place, to avoid requiring separate storage for operand
+// and result.
+//
+// This is an internal class. Some methods live in the .cc file, and are
+// instantiated only for the values of max_words we need.
+template <int max_words>
+class BigUnsigned {
+ public:
+ static_assert(max_words == 4 || max_words == 84,
+ "unsupported max_words value");
+
+ BigUnsigned() : size_(0), words_{} {}
+ explicit BigUnsigned(uint32_t v) : size_(v > 0 ? 1 : 0), words_{v} {}
+ explicit BigUnsigned(uint64_t v)
+ : size_(0),
+ words_{static_cast<uint32_t>(v & 0xffffffff),
+ static_cast<uint32_t>(v >> 32)} {
+ if (words_[1]) {
+ size_ = 2;
+ } else if (words_[0]) {
+ size_ = 1;
+ }
+ }
+
+ // Constructs a BigUnsigned from the given string_view containing a decimal
+ // value. If the input std::string is not a decimal integer, constructs a 0
+ // instead.
+ explicit BigUnsigned(absl::string_view sv) : size_(0), words_{} {
+ // Check for valid input, returning a 0 otherwise. This is reasonable
+ // behavior only because this constructor is for unit tests.
+ if (std::find_if_not(sv.begin(), sv.end(), ascii_isdigit) != sv.end() ||
+ sv.empty()) {
+ return;
+ }
+ int exponent_adjust =
+ ReadDigits(sv.data(), sv.data() + sv.size(), Digits10() + 1);
+ if (exponent_adjust > 0) {
+ MultiplyByTenToTheNth(exponent_adjust);
+ }
+ }
+
+ // Loads the mantissa value of a previously-parsed float.
+ //
+ // Returns the associated decimal exponent. The value of the parsed float is
+ // exactly *this * 10**exponent.
+ int ReadFloatMantissa(const ParsedFloat& fp, int significant_digits);
+
+ // Returns the number of decimal digits of precision this type provides. All
+ // numbers with this many decimal digits or fewer are representable by this
+ // type.
+ //
+ // Analagous to std::numeric_limits<BigUnsigned>::digits10.
+ static constexpr int Digits10() {
+ // 9975007/1035508 is very slightly less than log10(2**32).
+ return static_cast<uint64_t>(max_words) * 9975007 / 1035508;
+ }
+
+ // Shifts left by the given number of bits.
+ void ShiftLeft(int count) {
+ if (count > 0) {
+ const int word_shift = count / 32;
+ if (word_shift >= max_words) {
+ SetToZero();
+ return;
+ }
+ size_ = std::min(size_ + word_shift, max_words);
+ count %= 32;
+ if (count == 0) {
+ std::copy_backward(words_, words_ + size_ - word_shift, words_ + size_);
+ } else {
+ for (int i = std::min(size_, max_words - 1); i > word_shift; --i) {
+ words_[i] = (words_[i - word_shift] << count) |
+ (words_[i - word_shift - 1] >> (32 - count));
+ }
+ words_[word_shift] = words_[0] << count;
+ // Grow size_ if necessary.
+ if (size_ < max_words && words_[size_]) {
+ ++size_;
+ }
+ }
+ std::fill(words_, words_ + word_shift, 0u);
+ }
+ }
+
+
+ // Multiplies by v in-place.
+ void MultiplyBy(uint32_t v) {
+ if (size_ == 0 || v == 1) {
+ return;
+ }
+ if (v == 0) {
+ SetToZero();
+ return;
+ }
+ const uint64_t factor = v;
+ uint64_t window = 0;
+ for (int i = 0; i < size_; ++i) {
+ window += factor * words_[i];
+ words_[i] = window & 0xffffffff;
+ window >>= 32;
+ }
+ // If carry bits remain and there's space for them, grow size_.
+ if (window && size_ < max_words) {
+ words_[size_] = window & 0xffffffff;
+ ++size_;
+ }
+ }
+
+ void MultiplyBy(uint64_t v) {
+ uint32_t words[2];
+ words[0] = static_cast<uint32_t>(v);
+ words[1] = static_cast<uint32_t>(v >> 32);
+ if (words[1] == 0) {
+ MultiplyBy(words[0]);
+ } else {
+ MultiplyBy(2, words);
+ }
+ }
+
+ // Multiplies in place by 5 to the power of n. n must be non-negative.
+ void MultiplyByFiveToTheNth(int n) {
+ while (n >= kMaxSmallPowerOfFive) {
+ MultiplyBy(kFiveToNth[kMaxSmallPowerOfFive]);
+ n -= kMaxSmallPowerOfFive;
+ }
+ if (n > 0) {
+ MultiplyBy(kFiveToNth[n]);
+ }
+ }
+
+ // Multiplies in place by 10 to the power of n. n must be non-negative.
+ void MultiplyByTenToTheNth(int n) {
+ if (n > kMaxSmallPowerOfTen) {
+ // For large n, raise to a power of 5, then shift left by the same amount.
+ // (10**n == 5**n * 2**n.) This requires fewer multiplications overall.
+ MultiplyByFiveToTheNth(n);
+ ShiftLeft(n);
+ } else if (n > 0) {
+ // We can do this more quickly for very small N by using a single
+ // multiplication.
+ MultiplyBy(kTenToNth[n]);
+ }
+ }
+
+ // Returns the value of 5**n, for non-negative n. This implementation uses
+ // a lookup table, and is faster then seeding a BigUnsigned with 1 and calling
+ // MultiplyByFiveToTheNth().
+ static BigUnsigned FiveToTheNth(int n);
+
+ // Multiplies by another BigUnsigned, in-place.
+ template <int M>
+ void MultiplyBy(const BigUnsigned<M>& other) {
+ MultiplyBy(other.size(), other.words());
+ }
+
+ void SetToZero() {
+ std::fill(words_, words_ + size_, 0u);
+ size_ = 0;
+ }
+
+ // Returns the value of the nth word of this BigUnsigned. This is
+ // range-checked, and returns 0 on out-of-bounds accesses.
+ uint32_t GetWord(int index) const {
+ if (index < 0 || index >= size_) {
+ return 0;
+ }
+ return words_[index];
+ }
+
+ // Returns this integer as a decimal std::string. This is not used in the decimal-
+ // to-binary conversion; it is intended to aid in testing.
+ std::string ToString() const;
+
+ int size() const { return size_; }
+ const uint32_t* words() const { return words_; }
+
+ private:
+ // Reads the number between [begin, end), possibly containing a decimal point,
+ // into this BigUnsigned.
+ //
+ // Callers are required to ensure [begin, end) contains a valid number, with
+ // one or more decimal digits and at most one decimal point. This routine
+ // will behave unpredictably if these preconditions are not met.
+ //
+ // Only the first `significant_digits` digits are read. Digits beyond this
+ // limit are "sticky": If the final significant digit is 0 or 5, and if any
+ // dropped digit is nonzero, then that final significant digit is adjusted up
+ // to 1 or 6. This adjustment allows for precise rounding.
+ //
+ // Returns `exponent_adjustment`, a power-of-ten exponent adjustment to
+ // account for the decimal point and for dropped significant digits. After
+ // this function returns,
+ // actual_value_of_parsed_string ~= *this * 10**exponent_adjustment.
+ int ReadDigits(const char* begin, const char* end, int significant_digits);
+
+ // Performs a step of big integer multiplication. This computes the full
+ // (64-bit-wide) values that should be added at the given index (step), and
+ // adds to that location in-place.
+ //
+ // Because our math all occurs in place, we must multiply starting from the
+ // highest word working downward. (This is a bit more expensive due to the
+ // extra carries involved.)
+ //
+ // This must be called in steps, for each word to be calculated, starting from
+ // the high end and working down to 0. The first value of `step` should be
+ // `std::min(original_size + other.size_ - 2, max_words - 1)`.
+ // The reason for this expression is that multiplying the i'th word from one
+ // multiplicand and the j'th word of another multiplicand creates a
+ // two-word-wide value to be stored at the (i+j)'th element. The highest
+ // word indices we will access are `original_size - 1` from this object, and
+ // `other.size_ - 1` from our operand. Therefore,
+ // `original_size + other.size_ - 2` is the first step we should calculate,
+ // but limited on an upper bound by max_words.
+
+ // Working from high-to-low ensures that we do not overwrite the portions of
+ // the initial value of *this which are still needed for later steps.
+ //
+ // Once called with step == 0, *this contains the result of the
+ // multiplication.
+ //
+ // `original_size` is the size_ of *this before the first call to
+ // MultiplyStep(). `other_words` and `other_size` are the contents of our
+ // operand. `step` is the step to perform, as described above.
+ void MultiplyStep(int original_size, const uint32_t* other_words,
+ int other_size, int step);
+
+ void MultiplyBy(int other_size, const uint32_t* other_words) {
+ const int original_size = size_;
+ const int first_step =
+ std::min(original_size + other_size - 2, max_words - 1);
+ for (int step = first_step; step >= 0; --step) {
+ MultiplyStep(original_size, other_words, other_size, step);
+ }
+ }
+
+ // Adds a 32-bit value to the index'th word, with carry.
+ void AddWithCarry(int index, uint32_t value) {
+ if (value) {
+ while (index < max_words && value > 0) {
+ words_[index] += value;
+ // carry if we overflowed in this word:
+ if (value > words_[index]) {
+ value = 1;
+ ++index;
+ } else {
+ value = 0;
+ }
+ }
+ size_ = std::min(max_words, std::max(index + 1, size_));
+ }
+ }
+
+ void AddWithCarry(int index, uint64_t value) {
+ if (value && index < max_words) {
+ uint32_t high = value >> 32;
+ uint32_t low = value & 0xffffffff;
+ words_[index] += low;
+ if (words_[index] < low) {
+ ++high;
+ if (high == 0) {
+ // Carry from the low word caused our high word to overflow.
+ // Short circuit here to do the right thing.
+ AddWithCarry(index + 2, static_cast<uint32_t>(1));
+ return;
+ }
+ }
+ if (high > 0) {
+ AddWithCarry(index + 1, high);
+ } else {
+ // Normally 32-bit AddWithCarry() sets size_, but since we don't call
+ // it when `high` is 0, do it ourselves here.
+ size_ = std::min(max_words, std::max(index + 1, size_));
+ }
+ }
+ }
+
+ // Divide this in place by a constant divisor. Returns the remainder of the
+ // division.
+ template <uint32_t divisor>
+ uint32_t DivMod() {
+ uint64_t accumulator = 0;
+ for (int i = size_ - 1; i >= 0; --i) {
+ accumulator <<= 32;
+ accumulator += words_[i];
+ // accumulator / divisor will never overflow an int32_t in this loop
+ words_[i] = static_cast<uint32_t>(accumulator / divisor);
+ accumulator = accumulator % divisor;
+ }
+ while (size_ > 0 && words_[size_ - 1] == 0) {
+ --size_;
+ }
+ return static_cast<uint32_t>(accumulator);
+ }
+
+ // The number of elements in words_ that may carry significant values.
+ // All elements beyond this point are 0.
+ //
+ // When size_ is 0, this BigUnsigned stores the value 0.
+ // When size_ is nonzero, is *not* guaranteed that words_[size_ - 1] is
+ // nonzero. This can occur due to overflow truncation.
+ // In particular, x.size_ != y.size_ does *not* imply x != y.
+ int size_;
+ uint32_t words_[max_words];
+};
+
+// Compares two big integer instances.
+//
+// Returns -1 if lhs < rhs, 0 if lhs == rhs, and 1 if lhs > rhs.
+template <int N, int M>
+int Compare(const BigUnsigned<N>& lhs, const BigUnsigned<M>& rhs) {
+ int limit = std::max(lhs.size(), rhs.size());
+ for (int i = limit - 1; i >= 0; --i) {
+ const uint32_t lhs_word = lhs.GetWord(i);
+ const uint32_t rhs_word = rhs.GetWord(i);
+ if (lhs_word < rhs_word) {
+ return -1;
+ } else if (lhs_word > rhs_word) {
+ return 1;
+ }
+ }
+ return 0;
+}
+
+template <int N, int M>
+bool operator==(const BigUnsigned<N>& lhs, const BigUnsigned<M>& rhs) {
+ int limit = std::max(lhs.size(), rhs.size());
+ for (int i = 0; i < limit; ++i) {
+ if (lhs.GetWord(i) != rhs.GetWord(i)) {
+ return false;
+ }
+ }
+ return true;
+}
+
+template <int N, int M>
+bool operator!=(const BigUnsigned<N>& lhs, const BigUnsigned<M>& rhs) {
+ return !(lhs == rhs);
+}
+
+template <int N, int M>
+bool operator<(const BigUnsigned<N>& lhs, const BigUnsigned<M>& rhs) {
+ return Compare(lhs, rhs) == -1;
+}
+
+template <int N, int M>
+bool operator>(const BigUnsigned<N>& lhs, const BigUnsigned<M>& rhs) {
+ return rhs < lhs;
+}
+template <int N, int M>
+bool operator<=(const BigUnsigned<N>& lhs, const BigUnsigned<M>& rhs) {
+ return !(rhs < lhs);
+}
+template <int N, int M>
+bool operator>=(const BigUnsigned<N>& lhs, const BigUnsigned<M>& rhs) {
+ return !(lhs < rhs);
+}
+
+// Output operator for BigUnsigned, for testing purposes only.
+template <int N>
+std::ostream& operator<<(std::ostream& os, const BigUnsigned<N>& num) {
+ return os << num.ToString();
+}
+
+// Explicit instantiation declarations for the sizes of BigUnsigned that we
+// are using.
+//
+// For now, the choices of 4 and 84 are arbitrary; 4 is a small value that is
+// still bigger than an int128, and 84 is a large value we will want to use
+// in the from_chars implementation.
+//
+// Comments justifying the use of 84 belong in the from_chars implementation,
+// and will be added in a follow-up CL.
+extern template class BigUnsigned<4>;
+extern template class BigUnsigned<84>;
+
+} // namespace strings_internal
+} // namespace absl
+
+#endif // ABSL_STRINGS_INTERNAL_CHARCONV_BIGINT_H_
diff --git a/absl/strings/internal/charconv_bigint_test.cc b/absl/strings/internal/charconv_bigint_test.cc
new file mode 100644
index 00000000..9b635788
--- /dev/null
+++ b/absl/strings/internal/charconv_bigint_test.cc
@@ -0,0 +1,203 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/charconv_bigint.h"
+
+#include <string>
+
+#include "gtest/gtest.h"
+
+namespace absl {
+namespace strings_internal {
+
+TEST(BigUnsigned, ShiftLeft) {
+ {
+ // Check that 3 * 2**100 is calculated correctly
+ BigUnsigned<4> num(3u);
+ num.ShiftLeft(100);
+ EXPECT_EQ(num, BigUnsigned<4>("3802951800684688204490109616128"));
+ }
+ {
+ // Test that overflow is truncated properly.
+ // 15 is 4 bits long, and BigUnsigned<4> is a 128-bit bigint.
+ // Shifting left by 125 bits should truncate off the high bit, so that
+ // 15 << 125 == 7 << 125
+ // after truncation.
+ BigUnsigned<4> a(15u);
+ BigUnsigned<4> b(7u);
+ BigUnsigned<4> c(3u);
+ a.ShiftLeft(125);
+ b.ShiftLeft(125);
+ c.ShiftLeft(125);
+ EXPECT_EQ(a, b);
+ EXPECT_NE(a, c);
+ }
+ {
+ // Same test, larger bigint:
+ BigUnsigned<84> a(15u);
+ BigUnsigned<84> b(7u);
+ BigUnsigned<84> c(3u);
+ a.ShiftLeft(84 * 32 - 3);
+ b.ShiftLeft(84 * 32 - 3);
+ c.ShiftLeft(84 * 32 - 3);
+ EXPECT_EQ(a, b);
+ EXPECT_NE(a, c);
+ }
+ {
+ // Check that incrementally shifting has the same result as doing it all at
+ // once (attempting to capture corner cases.)
+ const std::string seed = "1234567890123456789012345678901234567890";
+ BigUnsigned<84> a(seed);
+ for (int i = 1; i <= 84 * 32; ++i) {
+ a.ShiftLeft(1);
+ BigUnsigned<84> b(seed);
+ b.ShiftLeft(i);
+ EXPECT_EQ(a, b);
+ }
+ // And we should have fully rotated all bits off by now:
+ EXPECT_EQ(a, BigUnsigned<84>(0u));
+ }
+}
+
+TEST(BigUnsigned, MultiplyByUint32) {
+ const BigUnsigned<84> factorial_100(
+ "933262154439441526816992388562667004907159682643816214685929638952175999"
+ "932299156089414639761565182862536979208272237582511852109168640000000000"
+ "00000000000000");
+ BigUnsigned<84> a(1u);
+ for (uint32_t i = 1; i <= 100; ++i) {
+ a.MultiplyBy(i);
+ }
+ EXPECT_EQ(a, BigUnsigned<84>(factorial_100));
+}
+
+TEST(BigUnsigned, MultiplyByBigUnsigned) {
+ {
+ // Put the terms of factorial_200 into two bigints, and multiply them
+ // together.
+ const BigUnsigned<84> factorial_200(
+ "7886578673647905035523632139321850622951359776871732632947425332443594"
+ "4996340334292030428401198462390417721213891963883025764279024263710506"
+ "1926624952829931113462857270763317237396988943922445621451664240254033"
+ "2918641312274282948532775242424075739032403212574055795686602260319041"
+ "7032406235170085879617892222278962370389737472000000000000000000000000"
+ "0000000000000000000000000");
+ BigUnsigned<84> evens(1u);
+ BigUnsigned<84> odds(1u);
+ for (uint32_t i = 1; i < 200; i += 2) {
+ odds.MultiplyBy(i);
+ evens.MultiplyBy(i + 1);
+ }
+ evens.MultiplyBy(odds);
+ EXPECT_EQ(evens, factorial_200);
+ }
+ {
+ // Multiply various powers of 10 together.
+ for (int a = 0 ; a < 700; a += 25) {
+ SCOPED_TRACE(a);
+ BigUnsigned<84> a_value("3" + std::string(a, '0'));
+ for (int b = 0; b < (700 - a); b += 25) {
+ SCOPED_TRACE(b);
+ BigUnsigned<84> b_value("2" + std::string(b, '0'));
+ BigUnsigned<84> expected_product("6" + std::string(a + b, '0'));
+ b_value.MultiplyBy(a_value);
+ EXPECT_EQ(b_value, expected_product);
+ }
+ }
+ }
+}
+
+TEST(BigUnsigned, MultiplyByOverflow) {
+ {
+ // Check that multiplcation overflow predictably truncates.
+
+ // A big int with all bits on.
+ BigUnsigned<4> all_bits_on("340282366920938463463374607431768211455");
+ // Modulo 2**128, this is equal to -1. Therefore the square of this,
+ // modulo 2**128, should be 1.
+ all_bits_on.MultiplyBy(all_bits_on);
+ EXPECT_EQ(all_bits_on, BigUnsigned<4>(1u));
+ }
+ {
+ // Try multiplying a large bigint by 2**50, and compare the result to
+ // shifting.
+ BigUnsigned<4> value_1("12345678901234567890123456789012345678");
+ BigUnsigned<4> value_2("12345678901234567890123456789012345678");
+ BigUnsigned<4> two_to_fiftieth(1u);
+ two_to_fiftieth.ShiftLeft(50);
+
+ value_1.ShiftLeft(50);
+ value_2.MultiplyBy(two_to_fiftieth);
+ EXPECT_EQ(value_1, value_2);
+ }
+}
+
+TEST(BigUnsigned, FiveToTheNth) {
+ {
+ // Sanity check that MultiplyByFiveToTheNth gives consistent answers, up to
+ // and including overflow.
+ for (int i = 0; i < 1160; ++i) {
+ SCOPED_TRACE(i);
+ BigUnsigned<84> value_1(123u);
+ BigUnsigned<84> value_2(123u);
+ value_1.MultiplyByFiveToTheNth(i);
+ for (int j = 0; j < i; j++) {
+ value_2.MultiplyBy(5u);
+ }
+ EXPECT_EQ(value_1, value_2);
+ }
+ }
+ {
+ // Check that the faster, table-lookup-based static method returns the same
+ // result that multiplying in-place would return, up to and including
+ // overflow.
+ for (int i = 0; i < 1160; ++i) {
+ SCOPED_TRACE(i);
+ BigUnsigned<84> value_1(1u);
+ value_1.MultiplyByFiveToTheNth(i);
+ BigUnsigned<84> value_2 = BigUnsigned<84>::FiveToTheNth(i);
+ EXPECT_EQ(value_1, value_2);
+ }
+ }
+}
+
+TEST(BigUnsigned, TenToTheNth) {
+ {
+ // Sanity check MultiplyByTenToTheNth.
+ for (int i = 0; i < 800; ++i) {
+ SCOPED_TRACE(i);
+ BigUnsigned<84> value_1(123u);
+ BigUnsigned<84> value_2(123u);
+ value_1.MultiplyByTenToTheNth(i);
+ for (int j = 0; j < i; j++) {
+ value_2.MultiplyBy(10u);
+ }
+ EXPECT_EQ(value_1, value_2);
+ }
+ }
+ {
+ // Alternate testing approach, taking advantage of the decimal parser.
+ for (int i = 0; i < 200; ++i) {
+ SCOPED_TRACE(i);
+ BigUnsigned<84> value_1(135u);
+ value_1.MultiplyByTenToTheNth(i);
+ BigUnsigned<84> value_2("135" + std::string(i, '0'));
+ EXPECT_EQ(value_1, value_2);
+ }
+ }
+}
+
+
+} // namespace strings_internal
+} // namespace absl
diff --git a/absl/strings/internal/charconv_parse.cc b/absl/strings/internal/charconv_parse.cc
new file mode 100644
index 00000000..a04cc676
--- /dev/null
+++ b/absl/strings/internal/charconv_parse.cc
@@ -0,0 +1,496 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/charconv_parse.h"
+#include "absl/strings/charconv.h"
+
+#include <cassert>
+#include <cstdint>
+#include <limits>
+
+#include "absl/strings/internal/memutil.h"
+
+namespace absl {
+namespace {
+
+// ParseFloat<10> will read the first 19 significant digits of the mantissa.
+// This number was chosen for multiple reasons.
+//
+// (a) First, for whatever integer type we choose to represent the mantissa, we
+// want to choose the largest possible number of decimal digits for that integer
+// type. We are using uint64_t, which can express any 19-digit unsigned
+// integer.
+//
+// (b) Second, we need to parse enough digits that the binary value of any
+// mantissa we capture has more bits of resolution than the mantissa
+// representation in the target float. Our algorithm requires at least 3 bits
+// of headway, but 19 decimal digits give a little more than that.
+//
+// The following static assertions verify the above comments:
+constexpr int kDecimalMantissaDigitsMax = 19;
+
+static_assert(std::numeric_limits<uint64_t>::digits10 ==
+ kDecimalMantissaDigitsMax,
+ "(a) above");
+
+// IEEE doubles, which we assume in Abseil, have 53 binary bits of mantissa.
+static_assert(std::numeric_limits<double>::is_iec559, "IEEE double assumed");
+static_assert(std::numeric_limits<double>::radix == 2, "IEEE double fact");
+static_assert(std::numeric_limits<double>::digits == 53, "IEEE double fact");
+
+// The lowest valued 19-digit decimal mantissa we can read still contains
+// sufficient information to reconstruct a binary mantissa.
+static_assert(1000000000000000000u > (uint64_t(1) << (53 + 3)), "(b) above");
+
+// ParseFloat<16> will read the first 15 significant digits of the mantissa.
+//
+// Because a base-16-to-base-2 conversion can be done exactly, we do not need
+// to maximize the number of scanned hex digits to improve our conversion. What
+// is required is to scan two more bits than the mantissa can represent, so that
+// we always round correctly.
+//
+// (One extra bit does not suffice to perform correct rounding, since a number
+// exactly halfway between two representable floats has unique rounding rules,
+// so we need to differentiate between a "halfway between" number and a "closer
+// to the larger value" number.)
+constexpr int kHexadecimalMantissaDigitsMax = 15;
+
+// The minimum number of significant bits that will be read from
+// kHexadecimalMantissaDigitsMax hex digits. We must subtract by three, since
+// the most significant digit can be a "1", which only contributes a single
+// significant bit.
+constexpr int kGuaranteedHexadecimalMantissaBitPrecision =
+ 4 * kHexadecimalMantissaDigitsMax - 3;
+
+static_assert(kGuaranteedHexadecimalMantissaBitPrecision >
+ std::numeric_limits<double>::digits + 2,
+ "kHexadecimalMantissaDigitsMax too small");
+
+// We also impose a limit on the number of significant digits we will read from
+// an exponent, to avoid having to deal with integer overflow. We use 9 for
+// this purpose.
+//
+// If we read a 9 digit exponent, the end result of the conversion will
+// necessarily be infinity or zero, depending on the sign of the exponent.
+// Therefore we can just drop extra digits on the floor without any extra
+// logic.
+constexpr int kDecimalExponentDigitsMax = 9;
+static_assert(std::numeric_limits<int>::digits10 >= kDecimalExponentDigitsMax,
+ "int type too small");
+
+// To avoid incredibly large inputs causing integer overflow for our exponent,
+// we impose an arbitrary but very large limit on the number of significant
+// digits we will accept. The implementation refuses to match a std::string with
+// more consecutive significant mantissa digits than this.
+constexpr int kDecimalDigitLimit = 50000000;
+
+// Corresponding limit for hexadecimal digit inputs. This is one fourth the
+// amount of kDecimalDigitLimit, since each dropped hexadecimal digit requires
+// a binary exponent adjustment of 4.
+constexpr int kHexadecimalDigitLimit = kDecimalDigitLimit / 4;
+
+// The largest exponent we can read is 999999999 (per
+// kDecimalExponentDigitsMax), and the largest exponent adjustment we can get
+// from dropped mantissa digits is 2 * kDecimalDigitLimit, and the sum of these
+// comfortably fits in an integer.
+//
+// We count kDecimalDigitLimit twice because there are independent limits for
+// numbers before and after the decimal point. (In the case where there are no
+// significant digits before the decimal point, there are independent limits for
+// post-decimal-point leading zeroes and for significant digits.)
+static_assert(999999999 + 2 * kDecimalDigitLimit <
+ std::numeric_limits<int>::max(),
+ "int type too small");
+static_assert(999999999 + 2 * (4 * kHexadecimalDigitLimit) <
+ std::numeric_limits<int>::max(),
+ "int type too small");
+
+// Returns true if the provided bitfield allows parsing an exponent value
+// (e.g., "1.5e100").
+bool AllowExponent(chars_format flags) {
+ bool fixed = (flags & chars_format::fixed) == chars_format::fixed;
+ bool scientific =
+ (flags & chars_format::scientific) == chars_format::scientific;
+ return scientific || !fixed;
+}
+
+// Returns true if the provided bitfield requires an exponent value be present.
+bool RequireExponent(chars_format flags) {
+ bool fixed = (flags & chars_format::fixed) == chars_format::fixed;
+ bool scientific =
+ (flags & chars_format::scientific) == chars_format::scientific;
+ return scientific && !fixed;
+}
+
+const int8_t kAsciiToInt[256] = {
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
+ 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1};
+
+// Returns true if `ch` is a digit in the given base
+template <int base>
+bool IsDigit(char ch);
+
+// Converts a valid `ch` to its digit value in the given base.
+template <int base>
+unsigned ToDigit(char ch);
+
+// Returns true if `ch` is the exponent delimiter for the given base.
+template <int base>
+bool IsExponentCharacter(char ch);
+
+// Returns the maximum number of significant digits we will read for a float
+// in the given base.
+template <int base>
+constexpr int MantissaDigitsMax();
+
+// Returns the largest consecutive run of digits we will accept when parsing a
+// number in the given base.
+template <int base>
+constexpr int DigitLimit();
+
+// Returns the amount the exponent must be adjusted by for each dropped digit.
+// (For decimal this is 1, since the digits are in base 10 and the exponent base
+// is also 10, but for hexadecimal this is 4, since the digits are base 16 but
+// the exponent base is 2.)
+template <int base>
+constexpr int DigitMagnitude();
+
+template <>
+bool IsDigit<10>(char ch) {
+ return ch >= '0' && ch <= '9';
+}
+template <>
+bool IsDigit<16>(char ch) {
+ return kAsciiToInt[static_cast<unsigned char>(ch)] >= 0;
+}
+
+template <>
+unsigned ToDigit<10>(char ch) {
+ return ch - '0';
+}
+template <>
+unsigned ToDigit<16>(char ch) {
+ return kAsciiToInt[static_cast<unsigned char>(ch)];
+}
+
+template <>
+bool IsExponentCharacter<10>(char ch) {
+ return ch == 'e' || ch == 'E';
+}
+
+template <>
+bool IsExponentCharacter<16>(char ch) {
+ return ch == 'p' || ch == 'P';
+}
+
+template <>
+constexpr int MantissaDigitsMax<10>() {
+ return kDecimalMantissaDigitsMax;
+}
+template <>
+constexpr int MantissaDigitsMax<16>() {
+ return kHexadecimalMantissaDigitsMax;
+}
+
+template <>
+constexpr int DigitLimit<10>() {
+ return kDecimalDigitLimit;
+}
+template <>
+constexpr int DigitLimit<16>() {
+ return kHexadecimalDigitLimit;
+}
+
+template <>
+constexpr int DigitMagnitude<10>() {
+ return 1;
+}
+template <>
+constexpr int DigitMagnitude<16>() {
+ return 4;
+}
+
+// Reads decimal digits from [begin, end) into *out. Returns the number of
+// digits consumed.
+//
+// After max_digits has been read, keeps consuming characters, but no longer
+// adjusts *out. If a nonzero digit is dropped this way, *dropped_nonzero_digit
+// is set; otherwise, it is left unmodified.
+//
+// If no digits are matched, returns 0 and leaves *out unchanged.
+//
+// ConsumeDigits does not protect against overflow on *out; max_digits must
+// be chosen with respect to type T to avoid the possibility of overflow.
+template <int base, typename T>
+std::size_t ConsumeDigits(const char* begin, const char* end, int max_digits,
+ T* out, bool* dropped_nonzero_digit) {
+ if (base == 10) {
+ assert(max_digits <= std::numeric_limits<T>::digits10);
+ } else if (base == 16) {
+ assert(max_digits * 4 <= std::numeric_limits<T>::digits);
+ }
+ const char* const original_begin = begin;
+ T accumulator = *out;
+ const char* significant_digits_end =
+ (end - begin > max_digits) ? begin + max_digits : end;
+ while (begin < significant_digits_end && IsDigit<base>(*begin)) {
+ // Do not guard against *out overflow; max_digits was chosen to avoid this.
+ // Do assert against it, to detect problems in debug builds.
+ auto digit = static_cast<T>(ToDigit<base>(*begin));
+ assert(accumulator * base >= accumulator);
+ accumulator *= base;
+ assert(accumulator + digit >= accumulator);
+ accumulator += digit;
+ ++begin;
+ }
+ bool dropped_nonzero = false;
+ while (begin < end && IsDigit<base>(*begin)) {
+ dropped_nonzero = dropped_nonzero || (*begin != '0');
+ ++begin;
+ }
+ if (dropped_nonzero && dropped_nonzero_digit != nullptr) {
+ *dropped_nonzero_digit = true;
+ }
+ *out = accumulator;
+ return begin - original_begin;
+}
+
+// Returns true if `v` is one of the chars allowed inside parentheses following
+// a NaN.
+bool IsNanChar(char v) {
+ return (v == '_') || (v >= '0' && v <= '9') || (v >= 'a' && v <= 'z') ||
+ (v >= 'A' && v <= 'Z');
+}
+
+// Checks the range [begin, end) for a strtod()-formatted infinity or NaN. If
+// one is found, sets `out` appropriately and returns true.
+bool ParseInfinityOrNan(const char* begin, const char* end,
+ strings_internal::ParsedFloat* out) {
+ if (end - begin < 3) {
+ return false;
+ }
+ switch (*begin) {
+ case 'i':
+ case 'I': {
+ // An infinity std::string consists of the characters "inf" or "infinity",
+ // case insensitive.
+ if (strings_internal::memcasecmp(begin + 1, "nf", 2) != 0) {
+ return false;
+ }
+ out->type = strings_internal::FloatType::kInfinity;
+ if (end - begin >= 8 &&
+ strings_internal::memcasecmp(begin + 3, "inity", 5) == 0) {
+ out->end = begin + 8;
+ } else {
+ out->end = begin + 3;
+ }
+ return true;
+ }
+ case 'n':
+ case 'N': {
+ // A NaN consists of the characters "nan", case insensitive, optionally
+ // followed by a parenthesized sequence of zero or more alphanumeric
+ // characters and/or underscores.
+ if (strings_internal::memcasecmp(begin + 1, "an", 2) != 0) {
+ return false;
+ }
+ out->type = strings_internal::FloatType::kNan;
+ out->end = begin + 3;
+ // NaN is allowed to be followed by a parenthesized std::string, consisting of
+ // only the characters [a-zA-Z0-9_]. Match that if it's present.
+ begin += 3;
+ if (begin < end && *begin == '(') {
+ const char* nan_begin = begin + 1;
+ while (nan_begin < end && IsNanChar(*nan_begin)) {
+ ++nan_begin;
+ }
+ if (nan_begin < end && *nan_begin == ')') {
+ // We found an extra NaN specifier range
+ out->subrange_begin = begin + 1;
+ out->subrange_end = nan_begin;
+ out->end = nan_begin + 1;
+ }
+ }
+ return true;
+ }
+ default:
+ return false;
+ }
+}
+} // namespace
+
+namespace strings_internal {
+
+template <int base>
+strings_internal::ParsedFloat ParseFloat(const char* begin, const char* end,
+ chars_format format_flags) {
+ strings_internal::ParsedFloat result;
+
+ // Exit early if we're given an empty range.
+ if (begin == end) return result;
+
+ // Handle the infinity and NaN cases.
+ if (ParseInfinityOrNan(begin, end, &result)) {
+ return result;
+ }
+
+ const char* const mantissa_begin = begin;
+ while (begin < end && *begin == '0') {
+ ++begin; // skip leading zeros
+ }
+ uint64_t mantissa = 0;
+
+ int exponent_adjustment = 0;
+ bool mantissa_is_inexact = false;
+ std::size_t pre_decimal_digits = ConsumeDigits<base>(
+ begin, end, MantissaDigitsMax<base>(), &mantissa, &mantissa_is_inexact);
+ begin += pre_decimal_digits;
+ int digits_left;
+ if (pre_decimal_digits >= DigitLimit<base>()) {
+ // refuse to parse pathological inputs
+ return result;
+ } else if (pre_decimal_digits > MantissaDigitsMax<base>()) {
+ // We dropped some non-fraction digits on the floor. Adjust our exponent
+ // to compensate.
+ exponent_adjustment =
+ static_cast<int>(pre_decimal_digits - MantissaDigitsMax<base>());
+ digits_left = 0;
+ } else {
+ digits_left =
+ static_cast<int>(MantissaDigitsMax<base>() - pre_decimal_digits);
+ }
+ if (begin < end && *begin == '.') {
+ ++begin;
+ if (mantissa == 0) {
+ // If we haven't seen any nonzero digits yet, keep skipping zeros. We
+ // have to adjust the exponent to reflect the changed place value.
+ const char* begin_zeros = begin;
+ while (begin < end && *begin == '0') {
+ ++begin;
+ }
+ std::size_t zeros_skipped = begin - begin_zeros;
+ if (zeros_skipped >= DigitLimit<base>()) {
+ // refuse to parse pathological inputs
+ return result;
+ }
+ exponent_adjustment -= static_cast<int>(zeros_skipped);
+ }
+ std::size_t post_decimal_digits = ConsumeDigits<base>(
+ begin, end, digits_left, &mantissa, &mantissa_is_inexact);
+ begin += post_decimal_digits;
+
+ // Since `mantissa` is an integer, each significant digit we read after
+ // the decimal point requires an adjustment to the exponent. "1.23e0" will
+ // be stored as `mantissa` == 123 and `exponent` == -2 (that is,
+ // "123e-2").
+ if (post_decimal_digits >= DigitLimit<base>()) {
+ // refuse to parse pathological inputs
+ return result;
+ } else if (post_decimal_digits > digits_left) {
+ exponent_adjustment -= digits_left;
+ } else {
+ exponent_adjustment -= post_decimal_digits;
+ }
+ }
+ // If we've found no mantissa whatsoever, this isn't a number.
+ if (mantissa_begin == begin) {
+ return result;
+ }
+ // A bare "." doesn't count as a mantissa either.
+ if (begin - mantissa_begin == 1 && *mantissa_begin == '.') {
+ return result;
+ }
+
+ if (mantissa_is_inexact) {
+ // We dropped significant digits on the floor. Handle this appropriately.
+ if (base == 10) {
+ // If we truncated significant decimal digits, store the full range of the
+ // mantissa for future big integer math for exact rounding.
+ result.subrange_begin = mantissa_begin;
+ result.subrange_end = begin;
+ } else if (base == 16) {
+ // If we truncated hex digits, reflect this fact by setting the low
+ // ("sticky") bit. This allows for correct rounding in all cases.
+ mantissa |= 1;
+ }
+ }
+ result.mantissa = mantissa;
+
+ const char* const exponent_begin = begin;
+ result.literal_exponent = 0;
+ bool found_exponent = false;
+ if (AllowExponent(format_flags) && begin < end &&
+ IsExponentCharacter<base>(*begin)) {
+ bool negative_exponent = false;
+ ++begin;
+ if (begin < end && *begin == '-') {
+ negative_exponent = true;
+ ++begin;
+ } else if (begin < end && *begin == '+') {
+ ++begin;
+ }
+ const char* const exponent_digits_begin = begin;
+ // Exponent is always expressed in decimal, even for hexadecimal floats.
+ begin += ConsumeDigits<10>(begin, end, kDecimalExponentDigitsMax,
+ &result.literal_exponent, nullptr);
+ if (begin == exponent_digits_begin) {
+ // there were no digits where we expected an exponent. We failed to read
+ // an exponent and should not consume the 'e' after all. Rewind 'begin'.
+ found_exponent = false;
+ begin = exponent_begin;
+ } else {
+ found_exponent = true;
+ if (negative_exponent) {
+ result.literal_exponent = -result.literal_exponent;
+ }
+ }
+ }
+
+ if (!found_exponent && RequireExponent(format_flags)) {
+ // Provided flags required an exponent, but none was found. This results
+ // in a failure to scan.
+ return result;
+ }
+
+ // Success!
+ result.type = strings_internal::FloatType::kNumber;
+ if (result.mantissa > 0) {
+ result.exponent = result.literal_exponent +
+ (DigitMagnitude<base>() * exponent_adjustment);
+ } else {
+ result.exponent = 0;
+ }
+ result.end = begin;
+ return result;
+}
+
+template ParsedFloat ParseFloat<10>(const char* begin, const char* end,
+ chars_format format_flags);
+template ParsedFloat ParseFloat<16>(const char* begin, const char* end,
+ chars_format format_flags);
+
+} // namespace strings_internal
+} // namespace absl
diff --git a/absl/strings/internal/charconv_parse.h b/absl/strings/internal/charconv_parse.h
new file mode 100644
index 00000000..7a5c0874
--- /dev/null
+++ b/absl/strings/internal/charconv_parse.h
@@ -0,0 +1,96 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_CHARCONV_PARSE_H_
+#define ABSL_STRINGS_INTERNAL_CHARCONV_PARSE_H_
+
+#include <cstdint>
+
+#include "absl/strings/charconv.h"
+
+namespace absl {
+namespace strings_internal {
+
+// Enum indicating whether a parsed float is a number or special value.
+enum class FloatType { kNumber, kInfinity, kNan };
+
+// The decomposed parts of a parsed `float` or `double`.
+struct ParsedFloat {
+ // Representation of the parsed mantissa, with the decimal point adjusted to
+ // make it an integer.
+ //
+ // During decimal scanning, this contains 19 significant digits worth of
+ // mantissa value. If digits beyond this point are found, they
+ // are truncated, and if any of these dropped digits are nonzero, then
+ // `mantissa` is inexact, and the full mantissa is stored in [subrange_begin,
+ // subrange_end).
+ //
+ // During hexadecimal scanning, this contains 15 significant hex digits worth
+ // of mantissa value. Digits beyond this point are sticky -- they are
+ // truncated, but if any dropped digits are nonzero, the low bit of mantissa
+ // will be set. (This allows for precise rounding, and avoids the need
+ // to store the full mantissa in [subrange_begin, subrange_end).)
+ uint64_t mantissa = 0;
+
+ // Floating point expontent. This reflects any decimal point adjustments and
+ // any truncated digits from the mantissa. The absolute value of the parsed
+ // number is represented by mantissa * (base ** exponent), where base==10 for
+ // decimal floats, and base==2 for hexadecimal floats.
+ int exponent = 0;
+
+ // The literal exponent value scanned from the input, or 0 if none was
+ // present. This does not reflect any adjustments applied to mantissa.
+ int literal_exponent = 0;
+
+ // The type of number scanned.
+ FloatType type = FloatType::kNumber;
+
+ // When non-null, [subrange_begin, subrange_end) marks a range of characters
+ // that require further processing. The meaning is dependent on float type.
+ // If type == kNumber and this is set, this is a "wide input": the input
+ // mantissa contained more than 19 digits. The range contains the full
+ // mantissa. It plus `literal_exponent` need to be examined to find the best
+ // floating point match.
+ // If type == kNan and this is set, the range marks the contents of a
+ // matched parenthesized character region after the NaN.
+ const char* subrange_begin = nullptr;
+ const char* subrange_end = nullptr;
+
+ // One-past-the-end of the successfully parsed region, or nullptr if no
+ // matching pattern was found.
+ const char* end = nullptr;
+};
+
+// Read the floating point number in the provided range, and populate
+// ParsedFloat accordingly.
+//
+// format_flags is a bitmask value specifying what patterns this API will match.
+// `scientific` and `fixed` are honored per std::from_chars rules
+// ([utility.from.chars], C++17): if exactly one of these bits is set, then an
+// exponent is required, or dislallowed, respectively.
+//
+// Template parameter `base` must be either 10 or 16. For base 16, a "0x" is
+// *not* consumed. The `hex` bit from format_flags is ignored by ParseFloat.
+template <int base>
+ParsedFloat ParseFloat(const char* begin, const char* end,
+ absl::chars_format format_flags);
+
+extern template ParsedFloat ParseFloat<10>(const char* begin, const char* end,
+ absl::chars_format format_flags);
+extern template ParsedFloat ParseFloat<16>(const char* begin, const char* end,
+ absl::chars_format format_flags);
+
+} // namespace strings_internal
+} // namespace absl
+#endif // ABSL_STRINGS_INTERNAL_CHARCONV_PARSE_H_
diff --git a/absl/strings/internal/charconv_parse_test.cc b/absl/strings/internal/charconv_parse_test.cc
new file mode 100644
index 00000000..1ff86004
--- /dev/null
+++ b/absl/strings/internal/charconv_parse_test.cc
@@ -0,0 +1,357 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/charconv_parse.h"
+
+#include <string>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/strings/str_cat.h"
+
+using absl::chars_format;
+using absl::strings_internal::FloatType;
+using absl::strings_internal::ParsedFloat;
+using absl::strings_internal::ParseFloat;
+
+namespace {
+
+// Check that a given std::string input is parsed to the expected mantissa and
+// exponent.
+//
+// Input std::string `s` must contain a '$' character. It marks the end of the
+// characters that should be consumed by the match. It is stripped from the
+// input to ParseFloat.
+//
+// If input std::string `s` contains '[' and ']' characters, these mark the region
+// of characters that should be marked as the "subrange". For NaNs, this is
+// the location of the extended NaN std::string. For numbers, this is the location
+// of the full, over-large mantissa.
+template <int base>
+void ExpectParsedFloat(std::string s, absl::chars_format format_flags,
+ FloatType expected_type, uint64_t expected_mantissa,
+ int expected_exponent,
+ int expected_literal_exponent = -999) {
+ SCOPED_TRACE(s);
+
+ int begin_subrange = -1;
+ int end_subrange = -1;
+ // If s contains '[' and ']', then strip these characters and set the subrange
+ // indices appropriately.
+ std::string::size_type open_bracket_pos = s.find('[');
+ if (open_bracket_pos != std::string::npos) {
+ begin_subrange = static_cast<int>(open_bracket_pos);
+ s.replace(open_bracket_pos, 1, "");
+ std::string::size_type close_bracket_pos = s.find(']');
+ ABSL_RAW_CHECK(close_bracket_pos != absl::string_view::npos,
+ "Test input contains [ without matching ]");
+ end_subrange = static_cast<int>(close_bracket_pos);
+ s.replace(close_bracket_pos, 1, "");
+ }
+ const std::string::size_type expected_characters_matched = s.find('$');
+ ABSL_RAW_CHECK(expected_characters_matched != std::string::npos,
+ "Input std::string must contain $");
+ s.replace(expected_characters_matched, 1, "");
+
+ ParsedFloat parsed =
+ ParseFloat<base>(s.data(), s.data() + s.size(), format_flags);
+
+ EXPECT_NE(parsed.end, nullptr);
+ if (parsed.end == nullptr) {
+ return; // The following tests are not useful if we fully failed to parse
+ }
+ EXPECT_EQ(parsed.type, expected_type);
+ if (begin_subrange == -1) {
+ EXPECT_EQ(parsed.subrange_begin, nullptr);
+ EXPECT_EQ(parsed.subrange_end, nullptr);
+ } else {
+ EXPECT_EQ(parsed.subrange_begin, s.data() + begin_subrange);
+ EXPECT_EQ(parsed.subrange_end, s.data() + end_subrange);
+ }
+ if (parsed.type == FloatType::kNumber) {
+ EXPECT_EQ(parsed.mantissa, expected_mantissa);
+ EXPECT_EQ(parsed.exponent, expected_exponent);
+ if (expected_literal_exponent != -999) {
+ EXPECT_EQ(parsed.literal_exponent, expected_literal_exponent);
+ }
+ }
+ auto characters_matched = static_cast<int>(parsed.end - s.data());
+ EXPECT_EQ(characters_matched, expected_characters_matched);
+}
+
+// Check that a given std::string input is parsed to the expected mantissa and
+// exponent.
+//
+// Input std::string `s` must contain a '$' character. It marks the end of the
+// characters that were consumed by the match.
+template <int base>
+void ExpectNumber(std::string s, absl::chars_format format_flags,
+ uint64_t expected_mantissa, int expected_exponent,
+ int expected_literal_exponent = -999) {
+ ExpectParsedFloat<base>(std::move(s), format_flags, FloatType::kNumber,
+ expected_mantissa, expected_exponent,
+ expected_literal_exponent);
+}
+
+// Check that a given std::string input is parsed to the given special value.
+//
+// This tests against both number bases, since infinities and NaNs have
+// identical representations in both modes.
+void ExpectSpecial(const std::string& s, absl::chars_format format_flags,
+ FloatType type) {
+ ExpectParsedFloat<10>(s, format_flags, type, 0, 0);
+ ExpectParsedFloat<16>(s, format_flags, type, 0, 0);
+}
+
+// Check that a given input std::string is not matched by Float.
+template <int base>
+void ExpectFailedParse(absl::string_view s, absl::chars_format format_flags) {
+ ParsedFloat parsed =
+ ParseFloat<base>(s.data(), s.data() + s.size(), format_flags);
+ EXPECT_EQ(parsed.end, nullptr);
+}
+
+TEST(ParseFloat, SimpleValue) {
+ // Test that various forms of floating point numbers all parse correctly.
+ ExpectNumber<10>("1.23456789e5$", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("1.23456789e+5$", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("1.23456789E5$", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("1.23456789e05$", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("123.456789e3$", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("0.000123456789e9$", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("123456.789$", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("123456789e-3$", chars_format::general, 123456789, -3);
+
+ ExpectNumber<16>("1.234abcdefp28$", chars_format::general, 0x1234abcdef, -8);
+ ExpectNumber<16>("1.234abcdefp+28$", chars_format::general, 0x1234abcdef, -8);
+ ExpectNumber<16>("1.234ABCDEFp28$", chars_format::general, 0x1234abcdef, -8);
+ ExpectNumber<16>("1.234AbCdEfP0028$", chars_format::general, 0x1234abcdef,
+ -8);
+ ExpectNumber<16>("123.4abcdefp20$", chars_format::general, 0x1234abcdef, -8);
+ ExpectNumber<16>("0.0001234abcdefp44$", chars_format::general, 0x1234abcdef,
+ -8);
+ ExpectNumber<16>("1234abcd.ef$", chars_format::general, 0x1234abcdef, -8);
+ ExpectNumber<16>("1234abcdefp-8$", chars_format::general, 0x1234abcdef, -8);
+
+ // ExpectNumber does not attempt to drop trailing zeroes.
+ ExpectNumber<10>("0001.2345678900e005$", chars_format::general, 12345678900,
+ -5);
+ ExpectNumber<16>("0001.234abcdef000p28$", chars_format::general,
+ 0x1234abcdef000, -20);
+
+ // Ensure non-matching characters after a number are ignored, even when they
+ // look like potentially matching characters.
+ ExpectNumber<10>("1.23456789e5$ ", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("1.23456789e5$e5e5", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("1.23456789e5$.25", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("1.23456789e5$-", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("1.23456789e5$PUPPERS!!!", chars_format::general, 123456789,
+ -3);
+ ExpectNumber<10>("123456.789$efghij", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("123456.789$e", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("123456.789$p5", chars_format::general, 123456789, -3);
+ ExpectNumber<10>("123456.789$.10", chars_format::general, 123456789, -3);
+
+ ExpectNumber<16>("1.234abcdefp28$ ", chars_format::general, 0x1234abcdef,
+ -8);
+ ExpectNumber<16>("1.234abcdefp28$p28", chars_format::general, 0x1234abcdef,
+ -8);
+ ExpectNumber<16>("1.234abcdefp28$.125", chars_format::general, 0x1234abcdef,
+ -8);
+ ExpectNumber<16>("1.234abcdefp28$-", chars_format::general, 0x1234abcdef, -8);
+ ExpectNumber<16>("1.234abcdefp28$KITTEHS!!!", chars_format::general,
+ 0x1234abcdef, -8);
+ ExpectNumber<16>("1234abcd.ef$ghijk", chars_format::general, 0x1234abcdef,
+ -8);
+ ExpectNumber<16>("1234abcd.ef$p", chars_format::general, 0x1234abcdef, -8);
+ ExpectNumber<16>("1234abcd.ef$.10", chars_format::general, 0x1234abcdef, -8);
+
+ // Ensure we can read a full resolution mantissa without overflow.
+ ExpectNumber<10>("9999999999999999999$", chars_format::general,
+ 9999999999999999999u, 0);
+ ExpectNumber<16>("fffffffffffffff$", chars_format::general,
+ 0xfffffffffffffffu, 0);
+
+ // Check that zero is consistently read.
+ ExpectNumber<10>("0$", chars_format::general, 0, 0);
+ ExpectNumber<16>("0$", chars_format::general, 0, 0);
+ ExpectNumber<10>("000000000000000000000000000000000000000$",
+ chars_format::general, 0, 0);
+ ExpectNumber<16>("000000000000000000000000000000000000000$",
+ chars_format::general, 0, 0);
+ ExpectNumber<10>("0000000000000000000000.000000000000000000$",
+ chars_format::general, 0, 0);
+ ExpectNumber<16>("0000000000000000000000.000000000000000000$",
+ chars_format::general, 0, 0);
+ ExpectNumber<10>("0.00000000000000000000000000000000e123456$",
+ chars_format::general, 0, 0);
+ ExpectNumber<16>("0.00000000000000000000000000000000p123456$",
+ chars_format::general, 0, 0);
+}
+
+TEST(ParseFloat, LargeDecimalMantissa) {
+ // After 19 significant decimal digits in the mantissa, ParsedFloat will
+ // truncate additional digits. We need to test that:
+ // 1) the truncation to 19 digits happens
+ // 2) the returned exponent reflects the dropped significant digits
+ // 3) a correct literal_exponent is set
+ //
+ // If and only if a significant digit is found after 19 digits, then the
+ // entirety of the mantissa in case the exact value is needed to make a
+ // rounding decision. The [ and ] characters below denote where such a
+ // subregion was marked by by ParseFloat. They are not part of the input.
+
+ // Mark a capture group only if a dropped digit is significant (nonzero).
+ ExpectNumber<10>("100000000000000000000000000$", chars_format::general,
+ 1000000000000000000,
+ /* adjusted exponent */ 8);
+
+ ExpectNumber<10>("123456789123456789100000000$", chars_format::general,
+ 1234567891234567891,
+ /* adjusted exponent */ 8);
+
+ ExpectNumber<10>("[123456789123456789123456789]$", chars_format::general,
+ 1234567891234567891,
+ /* adjusted exponent */ 8,
+ /* literal exponent */ 0);
+
+ ExpectNumber<10>("[123456789123456789100000009]$", chars_format::general,
+ 1234567891234567891,
+ /* adjusted exponent */ 8,
+ /* literal exponent */ 0);
+
+ ExpectNumber<10>("[123456789123456789120000000]$", chars_format::general,
+ 1234567891234567891,
+ /* adjusted exponent */ 8,
+ /* literal exponent */ 0);
+
+ // Leading zeroes should not count towards the 19 significant digit limit
+ ExpectNumber<10>("[00000000123456789123456789123456789]$",
+ chars_format::general, 1234567891234567891,
+ /* adjusted exponent */ 8,
+ /* literal exponent */ 0);
+
+ ExpectNumber<10>("00000000123456789123456789100000000$",
+ chars_format::general, 1234567891234567891,
+ /* adjusted exponent */ 8);
+
+ // Truncated digits after the decimal point should not cause a further
+ // exponent adjustment.
+ ExpectNumber<10>("1.234567891234567891e123$", chars_format::general,
+ 1234567891234567891, 105);
+ ExpectNumber<10>("[1.23456789123456789123456789]e123$", chars_format::general,
+ 1234567891234567891,
+ /* adjusted exponent */ 105,
+ /* literal exponent */ 123);
+
+ // Ensure we truncate, and not round. (The from_chars algorithm we use
+ // depends on our guess missing low, if it misses, so we need the rounding
+ // error to be downward.)
+ ExpectNumber<10>("[1999999999999999999999]$", chars_format::general,
+ 1999999999999999999,
+ /* adjusted exponent */ 3,
+ /* literal exponent */ 0);
+}
+
+TEST(ParseFloat, LargeHexadecimalMantissa) {
+ // After 15 significant hex digits in the mantissa, ParsedFloat will treat
+ // additional digits as sticky, We need to test that:
+ // 1) The truncation to 15 digits happens
+ // 2) The returned exponent reflects the dropped significant digits
+ // 3) If a nonzero digit is dropped, the low bit of mantissa is set.
+
+ ExpectNumber<16>("123456789abcdef123456789abcdef$", chars_format::general,
+ 0x123456789abcdef, 60);
+
+ // Leading zeroes should not count towards the 15 significant digit limit
+ ExpectNumber<16>("000000123456789abcdef123456789abcdef$",
+ chars_format::general, 0x123456789abcdef, 60);
+
+ // Truncated digits after the radix point should not cause a further
+ // exponent adjustment.
+ ExpectNumber<16>("1.23456789abcdefp100$", chars_format::general,
+ 0x123456789abcdef, 44);
+ ExpectNumber<16>("1.23456789abcdef123456789abcdefp100$",
+ chars_format::general, 0x123456789abcdef, 44);
+
+ // test sticky digit behavior. The low bit should be set iff any dropped
+ // digit is nonzero.
+ ExpectNumber<16>("123456789abcdee123456789abcdee$", chars_format::general,
+ 0x123456789abcdef, 60);
+ ExpectNumber<16>("123456789abcdee000000000000001$", chars_format::general,
+ 0x123456789abcdef, 60);
+ ExpectNumber<16>("123456789abcdee000000000000000$", chars_format::general,
+ 0x123456789abcdee, 60);
+}
+
+TEST(ParseFloat, ScientificVsFixed) {
+ // In fixed mode, an exponent is never matched (but the remainder of the
+ // number will be matched.)
+ ExpectNumber<10>("1.23456789$e5", chars_format::fixed, 123456789, -8);
+ ExpectNumber<10>("123456.789$", chars_format::fixed, 123456789, -3);
+ ExpectNumber<16>("1.234abcdef$p28", chars_format::fixed, 0x1234abcdef, -36);
+ ExpectNumber<16>("1234abcd.ef$", chars_format::fixed, 0x1234abcdef, -8);
+
+ // In scientific mode, numbers don't match *unless* they have an exponent.
+ ExpectNumber<10>("1.23456789e5$", chars_format::scientific, 123456789, -3);
+ ExpectFailedParse<10>("-123456.789$", chars_format::scientific);
+ ExpectNumber<16>("1.234abcdefp28$", chars_format::scientific, 0x1234abcdef,
+ -8);
+ ExpectFailedParse<16>("1234abcd.ef$", chars_format::scientific);
+}
+
+TEST(ParseFloat, Infinity) {
+ ExpectFailedParse<10>("in", chars_format::general);
+ ExpectFailedParse<16>("in", chars_format::general);
+ ExpectFailedParse<10>("inx", chars_format::general);
+ ExpectFailedParse<16>("inx", chars_format::general);
+ ExpectSpecial("inf$", chars_format::general, FloatType::kInfinity);
+ ExpectSpecial("Inf$", chars_format::general, FloatType::kInfinity);
+ ExpectSpecial("INF$", chars_format::general, FloatType::kInfinity);
+ ExpectSpecial("inf$inite", chars_format::general, FloatType::kInfinity);
+ ExpectSpecial("iNfInItY$", chars_format::general, FloatType::kInfinity);
+ ExpectSpecial("infinity$!!!", chars_format::general, FloatType::kInfinity);
+}
+
+TEST(ParseFloat, NaN) {
+ ExpectFailedParse<10>("na", chars_format::general);
+ ExpectFailedParse<16>("na", chars_format::general);
+ ExpectFailedParse<10>("nah", chars_format::general);
+ ExpectFailedParse<16>("nah", chars_format::general);
+ ExpectSpecial("nan$", chars_format::general, FloatType::kNan);
+ ExpectSpecial("NaN$", chars_format::general, FloatType::kNan);
+ ExpectSpecial("nAn$", chars_format::general, FloatType::kNan);
+ ExpectSpecial("NAN$", chars_format::general, FloatType::kNan);
+ ExpectSpecial("NaN$aNaNaNaNaBatman!", chars_format::general, FloatType::kNan);
+
+ // A parenthesized sequence of the characters [a-zA-Z0-9_] is allowed to
+ // appear after an NaN. Check that this is allowed, and that the correct
+ // characters are grouped.
+ //
+ // (The characters [ and ] in the pattern below delimit the expected matched
+ // subgroup; they are not part of the input passed to ParseFloat.)
+ ExpectSpecial("nan([0xabcdef])$", chars_format::general, FloatType::kNan);
+ ExpectSpecial("nan([0xabcdef])$...", chars_format::general, FloatType::kNan);
+ ExpectSpecial("nan([0xabcdef])$)...", chars_format::general, FloatType::kNan);
+ ExpectSpecial("nan([])$", chars_format::general, FloatType::kNan);
+ ExpectSpecial("nan([aAzZ09_])$", chars_format::general, FloatType::kNan);
+ // If the subgroup contains illegal characters, don't match it at all.
+ ExpectSpecial("nan$(bad-char)", chars_format::general, FloatType::kNan);
+ // Also cope with a missing close paren.
+ ExpectSpecial("nan$(0xabcdef", chars_format::general, FloatType::kNan);
+}
+
+} // namespace
diff --git a/absl/strings/numbers.cc b/absl/strings/numbers.cc
index 68ef7999..f842ed85 100644
--- a/absl/strings/numbers.cc
+++ b/absl/strings/numbers.cc
@@ -32,6 +32,7 @@
#include "absl/base/internal/raw_logging.h"
#include "absl/strings/ascii.h"
+#include "absl/strings/charconv.h"
#include "absl/strings/internal/bits.h"
#include "absl/strings/internal/memutil.h"
#include "absl/strings/str_cat.h"
@@ -40,51 +41,54 @@ namespace absl {
bool SimpleAtof(absl::string_view str, float* value) {
*value = 0.0;
- if (str.empty()) return false;
- char buf[32];
- std::unique_ptr<char[]> bigbuf;
- char* ptr = buf;
- if (str.size() > sizeof(buf) - 1) {
- bigbuf.reset(new char[str.size() + 1]);
- ptr = bigbuf.get();
- }
- memcpy(ptr, str.data(), str.size());
- ptr[str.size()] = '\0';
-
- char* endptr;
- *value = strtof(ptr, &endptr);
- if (endptr != ptr) {
- while (absl::ascii_isspace(*endptr)) ++endptr;
- }
- // Ignore range errors from strtod/strtof.
- // The values it returns on underflow and
- // overflow are the right fallback in a
- // robust setting.
- return *ptr != '\0' && *endptr == '\0';
+ str = StripAsciiWhitespace(str);
+ if (!str.empty() && str[0] == '+') {
+ str.remove_prefix(1);
+ }
+ auto result = absl::from_chars(str.data(), str.data() + str.size(), *value);
+ if (result.ec == std::errc::invalid_argument) {
+ return false;
+ }
+ if (result.ptr != str.data() + str.size()) {
+ // not all non-whitespace characters consumed
+ return false;
+ }
+ // from_chars() with DR 3801's current wording will return max() on
+ // overflow. SimpleAtof returns infinity instead.
+ if (result.ec == std::errc::result_out_of_range) {
+ if (*value > 1.0) {
+ *value = std::numeric_limits<float>::infinity();
+ } else if (*value < -1.0) {
+ *value = -std::numeric_limits<float>::infinity();
+ }
+ }
+ return true;
}
bool SimpleAtod(absl::string_view str, double* value) {
*value = 0.0;
- if (str.empty()) return false;
- char buf[32];
- std::unique_ptr<char[]> bigbuf;
- char* ptr = buf;
- if (str.size() > sizeof(buf) - 1) {
- bigbuf.reset(new char[str.size() + 1]);
- ptr = bigbuf.get();
- }
- memcpy(ptr, str.data(), str.size());
- ptr[str.size()] = '\0';
-
- char* endptr;
- *value = strtod(ptr, &endptr);
- if (endptr != ptr) {
- while (absl::ascii_isspace(*endptr)) ++endptr;
- }
- // Ignore range errors from strtod. The values it
- // returns on underflow and overflow are the right
- // fallback in a robust setting.
- return *ptr != '\0' && *endptr == '\0';
+ str = StripAsciiWhitespace(str);
+ if (!str.empty() && str[0] == '+') {
+ str.remove_prefix(1);
+ }
+ auto result = absl::from_chars(str.data(), str.data() + str.size(), *value);
+ if (result.ec == std::errc::invalid_argument) {
+ return false;
+ }
+ if (result.ptr != str.data() + str.size()) {
+ // not all non-whitespace characters consumed
+ return false;
+ }
+ // from_chars() with DR 3801's current wording will return max() on
+ // overflow. SimpleAtod returns infinity instead.
+ if (result.ec == std::errc::result_out_of_range) {
+ if (*value > 1.0) {
+ *value = std::numeric_limits<double>::infinity();
+ } else if (*value < -1.0) {
+ *value = -std::numeric_limits<double>::infinity();
+ }
+ }
+ return true;
}
namespace {
diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index 123536ea..372874e1 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel
@@ -149,12 +149,6 @@ cc_test(
size = "large",
srcs = ["mutex_test.cc"],
copts = ABSL_TEST_COPTS,
- tags = [
- "no_test_android_arm",
- "no_test_android_arm64",
- "no_test_android_x86",
- "no_test_loonix", # Too slow.
- ],
deps = [
":synchronization",
":thread_pool",
diff --git a/absl/time/BUILD.bazel b/absl/time/BUILD.bazel
index fe55fe1f..e793da87 100644
--- a/absl/time/BUILD.bazel
+++ b/absl/time/BUILD.bazel
@@ -44,6 +44,7 @@ cc_library(
"//absl/base",
"//absl/base:core_headers",
"//absl/numeric:int128",
+ "//absl/strings",
"//absl/time/internal/cctz:civil_time",
"//absl/time/internal/cctz:time_zone",
],
@@ -80,9 +81,6 @@ cc_test(
"time_zone_test.cc",
],
copts = ABSL_TEST_COPTS,
- tags = [
- "no_test_loonix",
- ],
deps = [
":test_util",
":time",
diff --git a/absl/time/CMakeLists.txt b/absl/time/CMakeLists.txt
index 72bb4d25..06272364 100644
--- a/absl/time/CMakeLists.txt
+++ b/absl/time/CMakeLists.txt
@@ -53,7 +53,7 @@ list(APPEND TIME_SRC
${TIME_PUBLIC_HEADERS}
${TIME_INTERNAL_HEADERS}
)
-set(TIME_PUBLIC_LIBRARIES absl::base absl::stacktrace absl::int128)
+set(TIME_PUBLIC_LIBRARIES absl::base absl::stacktrace absl::int128 absl::strings)
absl_library(
TARGET
diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index 82b4d989..c13fa79b 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -896,8 +896,7 @@ bool ParseDuration(const std::string& dur_string, Duration* d) {
return true;
}
-// TODO(absl-team): Remove once dependencies are removed.
-bool ParseFlag(const std::string& text, Duration* dst, std::string* /* err */) {
+bool ParseFlag(const std::string& text, Duration* dst, std::string* ) {
return ParseDuration(text, dst);
}
diff --git a/absl/time/format.cc b/absl/time/format.cc
index 5dc01bda..6edf2b5f 100644
--- a/absl/time/format.cc
+++ b/absl/time/format.cc
@@ -129,7 +129,6 @@ bool ParseTime(const std::string& format, const std::string& input, absl::TimeZo
return b;
}
-// TODO(absl-team): Remove once dependencies are removed.
// Functions required to support absl::Time flags.
bool ParseFlag(const std::string& text, absl::Time* t, std::string* error) {
return absl::ParseTime(RFC3339_full, text, absl::UTCTimeZone(), t, error);
diff --git a/absl/time/time.h b/absl/time/time.h
index 99c12bbd..ceec2de7 100644
--- a/absl/time/time.h
+++ b/absl/time/time.h
@@ -64,6 +64,7 @@
#include <utility>
#include "absl/base/port.h" // Needed for string vs std::string
+#include "absl/strings/string_view.h"
#include "absl/time/internal/cctz/include/cctz/time_zone.h"
namespace absl {
@@ -491,9 +492,6 @@ inline std::ostream& operator<<(std::ostream& os, Duration d) {
// `ZeroDuration()`. Parses "inf" and "-inf" as +/- `InfiniteDuration()`.
bool ParseDuration(const std::string& dur_string, Duration* d);
-// Flag Support
-// TODO(absl-team): Remove once dependencies are removed.
-
// ParseFlag()
//
bool ParseFlag(const std::string& text, Duration* dst, std::string* error);
@@ -993,8 +991,6 @@ bool ParseTime(const std::string& format, const std::string& input, Time* time,
bool ParseTime(const std::string& format, const std::string& input, TimeZone tz,
Time* time, std::string* err);
-// TODO(absl-team): Remove once dependencies are removed.
-
// ParseFlag()
// UnparseFlag()
//
diff --git a/absl/types/optional.h b/absl/types/optional.h
index 80a2d149..c837cdde 100644
--- a/absl/types/optional.h
+++ b/absl/types/optional.h
@@ -48,7 +48,7 @@ using std::optional;
using std::make_optional;
using std::nullopt_t;
using std::nullopt;
-}
+} // namespace absl
#else // ABSL_HAVE_STD_OPTIONAL
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 23:19:51 +0000