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Diffstat (limited to 'third_party/abseil_cpp/absl/strings/numbers.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/strings/numbers.h | 266 |
1 files changed, 266 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/strings/numbers.h b/third_party/abseil_cpp/absl/strings/numbers.h new file mode 100644 index 000000000000..d872cca5dc48 --- /dev/null +++ b/third_party/abseil_cpp/absl/strings/numbers.h @@ -0,0 +1,266 @@ +// +// Copyright 2017 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. +// +// ----------------------------------------------------------------------------- +// File: numbers.h +// ----------------------------------------------------------------------------- +// +// This package contains functions for converting strings to numbers. For +// converting numbers to strings, use `StrCat()` or `StrAppend()` in str_cat.h, +// which automatically detect and convert most number values appropriately. + +#ifndef ABSL_STRINGS_NUMBERS_H_ +#define ABSL_STRINGS_NUMBERS_H_ + +#ifdef __SSE4_2__ +#include <x86intrin.h> +#endif + +#include <cstddef> +#include <cstdlib> +#include <cstring> +#include <ctime> +#include <limits> +#include <string> +#include <type_traits> + +#include "absl/base/config.h" +#include "absl/base/internal/bits.h" +#ifdef __SSE4_2__ +// TODO(jorg): Remove this when we figure out the right way +// to swap bytes on SSE 4.2 that works with the compilers +// we claim to support. Also, add tests for the compiler +// that doesn't support the Intel _bswap64 intrinsic but +// does support all the SSE 4.2 intrinsics +#include "absl/base/internal/endian.h" +#endif +#include "absl/base/macros.h" +#include "absl/base/port.h" +#include "absl/numeric/int128.h" +#include "absl/strings/string_view.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN + +// SimpleAtoi() +// +// Converts the given string (optionally followed or preceded by ASCII +// whitespace) into an integer value, returning `true` if successful. The string +// must reflect a base-10 integer whose value falls within the range of the +// integer type (optionally preceded by a `+` or `-`). If any errors are +// encountered, this function returns `false`, leaving `out` in an unspecified +// state. +template <typename int_type> +ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view str, int_type* out); + +// SimpleAtof() +// +// Converts the given string (optionally followed or preceded by ASCII +// whitespace) into a float, which may be rounded on overflow or underflow, +// returning `true` if successful. +// See https://en.cppreference.com/w/c/string/byte/strtof for details about the +// allowed formats for `str`, except SimpleAtof() is locale-independent and will +// always use the "C" locale. If any errors are encountered, this function +// returns `false`, leaving `out` in an unspecified state. +ABSL_MUST_USE_RESULT bool SimpleAtof(absl::string_view str, float* out); + +// SimpleAtod() +// +// Converts the given string (optionally followed or preceded by ASCII +// whitespace) into a double, which may be rounded on overflow or underflow, +// returning `true` if successful. +// See https://en.cppreference.com/w/c/string/byte/strtof for details about the +// allowed formats for `str`, except SimpleAtod is locale-independent and will +// always use the "C" locale. If any errors are encountered, this function +// returns `false`, leaving `out` in an unspecified state. +ABSL_MUST_USE_RESULT bool SimpleAtod(absl::string_view str, double* out); + +// SimpleAtob() +// +// Converts the given string into a boolean, returning `true` if successful. +// The following case-insensitive strings are interpreted as boolean `true`: +// "true", "t", "yes", "y", "1". The following case-insensitive strings +// are interpreted as boolean `false`: "false", "f", "no", "n", "0". If any +// errors are encountered, this function returns `false`, leaving `out` in an +// unspecified state. +ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* out); + +ABSL_NAMESPACE_END +} // namespace absl + +// End of public API. Implementation details follow. + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace numbers_internal { + +// Digit conversion. +ABSL_DLL extern const char kHexChar[17]; // 0123456789abcdef +ABSL_DLL extern const char + kHexTable[513]; // 000102030405060708090a0b0c0d0e0f1011... +ABSL_DLL extern const char + two_ASCII_digits[100][2]; // 00, 01, 02, 03... + +// Writes a two-character representation of 'i' to 'buf'. 'i' must be in the +// range 0 <= i < 100, and buf must have space for two characters. Example: +// char buf[2]; +// PutTwoDigits(42, buf); +// // buf[0] == '4' +// // buf[1] == '2' +inline void PutTwoDigits(size_t i, char* buf) { + assert(i < 100); + memcpy(buf, two_ASCII_digits[i], 2); +} + +// safe_strto?() functions for implementing SimpleAtoi() +bool safe_strto32_base(absl::string_view text, int32_t* value, int base); +bool safe_strto64_base(absl::string_view text, int64_t* value, int base); +bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base); +bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base); +bool safe_strtou128_base(absl::string_view text, absl::uint128* value, + int base); + +static const int kFastToBufferSize = 32; +static const int kSixDigitsToBufferSize = 16; + +// Helper function for fast formatting of floating-point values. +// The result is the same as printf's "%g", a.k.a. "%.6g"; that is, six +// significant digits are returned, trailing zeros are removed, and numbers +// outside the range 0.0001-999999 are output using scientific notation +// (1.23456e+06). This routine is heavily optimized. +// Required buffer size is `kSixDigitsToBufferSize`. +size_t SixDigitsToBuffer(double d, char* buffer); + +// These functions are intended for speed. All functions take an output buffer +// as an argument and return a pointer to the last byte they wrote, which is the +// terminating '\0'. At most `kFastToBufferSize` bytes are written. +char* FastIntToBuffer(int32_t, char*); +char* FastIntToBuffer(uint32_t, char*); +char* FastIntToBuffer(int64_t, char*); +char* FastIntToBuffer(uint64_t, char*); + +// For enums and integer types that are not an exact match for the types above, +// use templates to call the appropriate one of the four overloads above. +template <typename int_type> +char* FastIntToBuffer(int_type i, char* buffer) { + static_assert(sizeof(i) <= 64 / 8, + "FastIntToBuffer works only with 64-bit-or-less integers."); + // TODO(jorg): This signed-ness check is used because it works correctly + // with enums, and it also serves to check that int_type is not a pointer. + // If one day something like std::is_signed<enum E> works, switch to it. + if (static_cast<int_type>(1) - 2 < 0) { // Signed + if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit + return FastIntToBuffer(static_cast<int64_t>(i), buffer); + } else { // 32-bit or less + return FastIntToBuffer(static_cast<int32_t>(i), buffer); + } + } else { // Unsigned + if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit + return FastIntToBuffer(static_cast<uint64_t>(i), buffer); + } else { // 32-bit or less + return FastIntToBuffer(static_cast<uint32_t>(i), buffer); + } + } +} + +// Implementation of SimpleAtoi, generalized to support arbitrary base (used +// with base different from 10 elsewhere in Abseil implementation). +template <typename int_type> +ABSL_MUST_USE_RESULT bool safe_strtoi_base(absl::string_view s, int_type* out, + int base) { + static_assert(sizeof(*out) == 4 || sizeof(*out) == 8, + "SimpleAtoi works only with 32-bit or 64-bit integers."); + static_assert(!std::is_floating_point<int_type>::value, + "Use SimpleAtof or SimpleAtod instead."); + bool parsed; + // TODO(jorg): This signed-ness check is used because it works correctly + // with enums, and it also serves to check that int_type is not a pointer. + // If one day something like std::is_signed<enum E> works, switch to it. + if (static_cast<int_type>(1) - 2 < 0) { // Signed + if (sizeof(*out) == 64 / 8) { // 64-bit + int64_t val; + parsed = numbers_internal::safe_strto64_base(s, &val, base); + *out = static_cast<int_type>(val); + } else { // 32-bit + int32_t val; + parsed = numbers_internal::safe_strto32_base(s, &val, base); + *out = static_cast<int_type>(val); + } + } else { // Unsigned + if (sizeof(*out) == 64 / 8) { // 64-bit + uint64_t val; + parsed = numbers_internal::safe_strtou64_base(s, &val, base); + *out = static_cast<int_type>(val); + } else { // 32-bit + uint32_t val; + parsed = numbers_internal::safe_strtou32_base(s, &val, base); + *out = static_cast<int_type>(val); + } + } + return parsed; +} + +// FastHexToBufferZeroPad16() +// +// Outputs `val` into `out` as if by `snprintf(out, 17, "%016x", val)` but +// without the terminating null character. Thus `out` must be of length >= 16. +// Returns the number of non-pad digits of the output (it can never be zero +// since 0 has one digit). +inline size_t FastHexToBufferZeroPad16(uint64_t val, char* out) { +#ifdef __SSE4_2__ + uint64_t be = absl::big_endian::FromHost64(val); + const auto kNibbleMask = _mm_set1_epi8(0xf); + const auto kHexDigits = _mm_setr_epi8('0', '1', '2', '3', '4', '5', '6', '7', + '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'); + auto v = _mm_loadl_epi64(reinterpret_cast<__m128i*>(&be)); // load lo dword + auto v4 = _mm_srli_epi64(v, 4); // shift 4 right + auto il = _mm_unpacklo_epi8(v4, v); // interleave bytes + auto m = _mm_and_si128(il, kNibbleMask); // mask out nibbles + auto hexchars = _mm_shuffle_epi8(kHexDigits, m); // hex chars + _mm_storeu_si128(reinterpret_cast<__m128i*>(out), hexchars); +#else + for (int i = 0; i < 8; ++i) { + auto byte = (val >> (56 - 8 * i)) & 0xFF; + auto* hex = &absl::numbers_internal::kHexTable[byte * 2]; + std::memcpy(out + 2 * i, hex, 2); + } +#endif + // | 0x1 so that even 0 has 1 digit. + return 16 - absl::base_internal::CountLeadingZeros64(val | 0x1) / 4; +} + +} // namespace numbers_internal + +// SimpleAtoi() +// +// Converts a string to an integer, using `safe_strto?()` functions for actual +// parsing, returning `true` if successful. The `safe_strto?()` functions apply +// strict checking; the string must be a base-10 integer, optionally followed or +// preceded by ASCII whitespace, with a value in the range of the corresponding +// integer type. +template <typename int_type> +ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view str, int_type* out) { + return numbers_internal::safe_strtoi_base(str, out, 10); +} + +ABSL_MUST_USE_RESULT inline bool SimpleAtoi(absl::string_view str, + absl::uint128* out) { + return numbers_internal::safe_strtou128_base(str, out, 10); +} + +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_NUMBERS_H_ |