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authorGravatar Abseil Team <absl-team@google.com>2018-05-14 13:41:38 -0700
committerGravatar jueminyang <jueminyang@google.com>2018-05-15 11:00:30 -0400
commit04dd99d8c1813ded74cd2a9c90ecb7eaa2d68ab1 (patch)
treebcbac48462be4c3d39c1dcf933b55ea98f3928e8 /absl/strings
parentadd89fd0e4bfd7d874bb55b67f4e13bf8beca762 (diff)
- abe587c2360b21f085b7d65a77d840015bc04cf6 Factor an internal interface into its own header, as it w... by Greg Falcon <gfalcon@google.com>
- 2201f1644336e64280dbd20207d8fbc3bfea2bf4 Internal change. by Abseil Team <absl-team@google.com> - 94e6b5b20d2cc754c99a18c575a4f1f3cd1f28d4 Rename no_throw_ctor to nothrow_ctor to match the standar... by Abseil Team <absl-team@google.com> - 86aa34d2129c4914c5133b7b619480aae786288e Update header files in debugging target by Tom Manshreck <shreck@google.com> - ed234519ced458724a7267b8fdf184eaae1c97c7 Remove CMAKE_CXX_WARNING_VLA from our c++ flags in the cm... by Jon Cohen <cohenjon@google.com> GitOrigin-RevId: abe587c2360b21f085b7d65a77d840015bc04cf6 Change-Id: I92f9301c69419d3830c358b88984967185aa33f6
Diffstat (limited to 'absl/strings')
-rw-r--r--absl/strings/BUILD.bazel1
-rw-r--r--absl/strings/CMakeLists.txt1
-rw-r--r--absl/strings/internal/bits.h53
-rw-r--r--absl/strings/numbers.cc17
4 files changed, 58 insertions, 14 deletions
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 13badb7b..1e52312b 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -84,6 +84,7 @@ cc_library(
"internal/utf8.cc",
],
hdrs = [
+ "internal/bits.h",
"internal/char_map.h",
"internal/ostringstream.h",
"internal/resize_uninitialized.h",
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index 83cb934d..9dc47328 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -31,6 +31,7 @@ list(APPEND STRINGS_PUBLIC_HEADERS
list(APPEND STRINGS_INTERNAL_HEADERS
+ "internal/bits.h"
"internal/char_map.h"
"internal/memutil.h"
"internal/ostringstream.h"
diff --git a/absl/strings/internal/bits.h b/absl/strings/internal/bits.h
new file mode 100644
index 00000000..901082cc
--- /dev/null
+++ b/absl/strings/internal/bits.h
@@ -0,0 +1,53 @@
+// 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_BITS_H_
+#define ABSL_STRINGS_INTERNAL_BITS_H_
+
+#include <cstdint>
+
+#if defined(_MSC_VER) && defined(_M_X64)
+#include <intrin.h>
+#pragma intrinsic(_BitScanReverse64)
+#endif
+
+namespace absl {
+namespace strings_internal {
+
+// Returns the number of leading 0 bits in a 64-bit value.
+inline int CountLeadingZeros64(uint64_t n) {
+#if defined(__GNUC__)
+ static_assert(sizeof(unsigned long long) == sizeof(n), // NOLINT(runtime/int)
+ "__builtin_clzll does not take 64bit arg");
+ return n == 0 ? 64 : __builtin_clzll(n);
+#elif defined(_MSC_VER) && defined(_M_X64)
+ unsigned long result; // NOLINT(runtime/int)
+ if (_BitScanReverse64(&result, n)) {
+ return 63 - result;
+ }
+ return 64;
+#else
+ int zeroes = 60;
+ if (n >> 32) zeroes -= 32, n >>= 32;
+ if (n >> 16) zeroes -= 16, n >>= 16;
+ if (n >> 8) zeroes -= 8, n >>= 8;
+ if (n >> 4) zeroes -= 4, n >>= 4;
+ return "\4\3\2\2\1\1\1\1\0\0\0\0\0\0\0\0"[n] + zeroes;
+#endif
+}
+
+} // namespace strings_internal
+} // namespace absl
+
+#endif // ABSL_STRINGS_INTERNAL_BITS_H_
diff --git a/absl/strings/numbers.cc b/absl/strings/numbers.cc
index b4140b36..68ef7999 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/internal/bits.h"
#include "absl/strings/internal/memutil.h"
#include "absl/strings/str_cat.h"
@@ -302,18 +303,6 @@ char* numbers_internal::FastIntToBuffer(int64_t i, char* buffer) {
return numbers_internal::FastIntToBuffer(u, buffer);
}
-// Returns the number of leading 0 bits in a 64-bit value.
-// TODO(jorg): Replace with builtin_clzll if available.
-// Are we shipping util/bits in absl?
-static inline int CountLeadingZeros64(uint64_t n) {
- int zeroes = 60;
- if (n >> 32) zeroes -= 32, n >>= 32;
- if (n >> 16) zeroes -= 16, n >>= 16;
- if (n >> 8) zeroes -= 8, n >>= 8;
- if (n >> 4) zeroes -= 4, n >>= 4;
- return "\4\3\2\2\1\1\1\1\0\0\0\0\0\0\0\0"[n] + zeroes;
-}
-
// Given a 128-bit number expressed as a pair of uint64_t, high half first,
// return that number multiplied by the given 32-bit value. If the result is
// too large to fit in a 128-bit number, divide it by 2 until it fits.
@@ -351,7 +340,7 @@ static std::pair<uint64_t, uint64_t> Mul32(std::pair<uint64_t, uint64_t> num,
uint64_t bits128_up = (bits96_127 >> 32) + (bits64_127 < bits64_95);
if (bits128_up == 0) return {bits64_127, bits0_63};
- int shift = 64 - CountLeadingZeros64(bits128_up);
+ int shift = 64 - strings_internal::CountLeadingZeros64(bits128_up);
uint64_t lo = (bits0_63 >> shift) + (bits64_127 << (64 - shift));
uint64_t hi = (bits64_127 >> shift) + (bits128_up << (64 - shift));
return {hi, lo};
@@ -382,7 +371,7 @@ static std::pair<uint64_t, uint64_t> PowFive(uint64_t num, int expfive) {
5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5,
5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5};
result = Mul32(result, powers_of_five[expfive & 15]);
- int shift = CountLeadingZeros64(result.first);
+ int shift = strings_internal::CountLeadingZeros64(result.first);
if (shift != 0) {
result.first = (result.first << shift) + (result.second >> (64 - shift));
result.second = (result.second << shift);