diff options
Diffstat (limited to 'absl/strings/internal/str_format/float_conversion.cc')
| -rw-r--r-- | absl/strings/internal/str_format/float_conversion.cc | 54 |
1 files changed, 36 insertions, 18 deletions
diff --git a/absl/strings/internal/str_format/float_conversion.cc b/absl/strings/internal/str_format/float_conversion.cc index 20aeada5..b1c40684 100644 --- a/absl/strings/internal/str_format/float_conversion.cc +++ b/absl/strings/internal/str_format/float_conversion.cc @@ -1,3 +1,17 @@ +// Copyright 2020 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 +// +// https://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/str_format/float_conversion.h" #include <string.h> @@ -10,11 +24,12 @@ #include "absl/base/attributes.h" #include "absl/base/config.h" -#include "absl/base/internal/bits.h" #include "absl/base/optimization.h" #include "absl/functional/function_ref.h" #include "absl/meta/type_traits.h" +#include "absl/numeric/bits.h" #include "absl/numeric/int128.h" +#include "absl/numeric/internal/representation.h" #include "absl/strings/numbers.h" #include "absl/types/optional.h" #include "absl/types/span.h" @@ -25,6 +40,8 @@ namespace str_format_internal { namespace { +using ::absl::numeric_internal::IsDoubleDouble; + // The code below wants to avoid heap allocations. // To do so it needs to allocate memory on the stack. // `StackArray` will allocate memory on the stack in the form of a uint32_t @@ -98,12 +115,15 @@ inline uint64_t DivideBy10WithCarry(uint64_t *v, uint64_t carry) { return next_carry % divisor; } +using MaxFloatType = + typename std::conditional<IsDoubleDouble(), double, long double>::type; + // Generates the decimal representation for an integer of the form `v * 2^exp`, // where `v` and `exp` are both positive integers. // It generates the digits from the left (ie the most significant digit first) // to allow for direct printing into the sink. // -// Requires `0 <= exp` and `exp <= numeric_limits<long double>::max_exponent`. +// Requires `0 <= exp` and `exp <= numeric_limits<MaxFloatType>::max_exponent`. class BinaryToDecimal { static constexpr int ChunksNeeded(int exp) { // We will left shift a uint128 by `exp` bits, so we need `128+exp` total @@ -118,10 +138,10 @@ class BinaryToDecimal { static void RunConversion(uint128 v, int exp, absl::FunctionRef<void(BinaryToDecimal)> f) { assert(exp > 0); - assert(exp <= std::numeric_limits<long double>::max_exponent); + assert(exp <= std::numeric_limits<MaxFloatType>::max_exponent); static_assert( - StackArray::kMaxCapacity >= - ChunksNeeded(std::numeric_limits<long double>::max_exponent), + static_cast<int>(StackArray::kMaxCapacity) >= + ChunksNeeded(std::numeric_limits<MaxFloatType>::max_exponent), ""); StackArray::RunWithCapacity( @@ -218,14 +238,14 @@ class BinaryToDecimal { // Converts a value of the form `x * 2^-exp` into a sequence of decimal digits. // Requires `-exp < 0` and -// `-exp >= limits<long double>::min_exponent - limits<long double>::digits`. +// `-exp >= limits<MaxFloatType>::min_exponent - limits<MaxFloatType>::digits`. class FractionalDigitGenerator { public: // Run the conversion for `v * 2^exp` and call `f(generator)`. // This function will allocate enough stack space to perform the conversion. static void RunConversion( uint128 v, int exp, absl::FunctionRef<void(FractionalDigitGenerator)> f) { - using Limits = std::numeric_limits<long double>; + using Limits = std::numeric_limits<MaxFloatType>; assert(-exp < 0); assert(-exp >= Limits::min_exponent - 128); static_assert(StackArray::kMaxCapacity >= @@ -301,12 +321,11 @@ class FractionalDigitGenerator { }; // Count the number of leading zero bits. -int LeadingZeros(uint64_t v) { return base_internal::CountLeadingZeros64(v); } +int LeadingZeros(uint64_t v) { return countl_zero(v); } int LeadingZeros(uint128 v) { auto high = static_cast<uint64_t>(v >> 64); auto low = static_cast<uint64_t>(v); - return high != 0 ? base_internal::CountLeadingZeros64(high) - : 64 + base_internal::CountLeadingZeros64(low); + return high != 0 ? countl_zero(high) : 64 + countl_zero(low); } // Round up the text digits starting at `p`. @@ -858,10 +877,10 @@ void FormatA(const HexFloatTypeParams float_traits, Int mantissa, int exp, // This buffer holds the "0x1.ab1de3" portion of "0x1.ab1de3pe+2". Compute the // size with long double which is the largest of the floats. constexpr size_t kBufSizeForHexFloatRepr = - 2 // 0x - + std::numeric_limits<long double>::digits / 4 // number of hex digits - + 1 // round up - + 1; // "." (dot) + 2 // 0x + + std::numeric_limits<MaxFloatType>::digits / 4 // number of hex digits + + 1 // round up + + 1; // "." (dot) char digits_buffer[kBufSizeForHexFloatRepr]; char *digits_iter = digits_buffer; const char *const digits = @@ -1380,10 +1399,9 @@ bool FloatToSink(const Float v, const FormatConversionSpecImpl &conv, bool ConvertFloatImpl(long double v, const FormatConversionSpecImpl &conv, FormatSinkImpl *sink) { - if (std::numeric_limits<long double>::digits == - 2 * std::numeric_limits<double>::digits) { - // This is the `double-double` representation of `long double`. - // We do not handle it natively. Fallback to snprintf. + if (IsDoubleDouble()) { + // This is the `double-double` representation of `long double`. We do not + // handle it natively. Fallback to snprintf. return FallbackToSnprintf(v, conv, sink); } |