tvl-depot/absl/strings/internal/charconv_parse.h

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-- f28d30df5769bb832dec3ff36d2fcd2bcdf494a3 by Shaindel Schwartz <shaindel@google.com>: Internal change PiperOrigin-RevId: 201046831 -- 711715a78b7e53dfaafd4d7f08a74e76db22af88 by Mark Barolak <mbar@google.com>: Internal fix PiperOrigin-RevId: 201043684 -- 64b53edd6bf1fa48f74e7f5d33f00f80d5089147 by Shaindel Schwartz <shaindel@google.com>: Remove extra whitespace PiperOrigin-RevId: 201041989 -- 0bdd2a0b33657b688e4a04aeba9ebba47e4dc6ca by Shaindel Schwartz <shaindel@google.com>: Whitespace fix. PiperOrigin-RevId: 201034413 -- 3deb0ac296ef1b74c4789e114a8a8bf53253f26b by Shaindel Schwartz <shaindel@google.com>: Scrub build tags. No functional changes. PiperOrigin-RevId: 201032927 -- da75d0f8b73baa7e8f4e9a092bba546012ed3b71 by Alex Strelnikov <strel@google.com>: Internal change. PiperOrigin-RevId: 201026131 -- 6815d80caa19870d0c441b6b9816c68db41393a5 by Tom Manshreck <shreck@google.com>: Add documentation for our LTS snapshot branches PiperOrigin-RevId: 201025191 -- 64c3b02006f39e6a8127bbabf9ec947fb45b6504 by Greg Falcon <gfalcon@google.com>: Provide absl::from_chars for double and float types. This is a forward-compatible implementation of std::from_chars from C++17. This provides exact "round_to_nearest" conversions, and has some nice properties: * Works with string_view (it can convert numbers from non-NUL-terminated buffers) * Never allocates memory * Faster than the standard library strtod() in our toolchain * Uses integer math in its calculations, so is unaffected by floating point environment * Unaffected by C locale Also change SimpleAtod/SimpleAtoi to use this new API under the hood. PiperOrigin-RevId: 201003324 -- 542869258eb100779497c899103dc96aced52749 by Greg Falcon <gfalcon@google.com>: Internal change PiperOrigin-RevId: 200999200 -- 3aba192775c7f80e2cd7f221b0a73537823c54ea by Gennadiy Rozental <rogeeff@google.com>: Internal change PiperOrigin-RevId: 200947470 -- daf9b9feedd748d5364a4c06165b7cb7604d3e1e by Mark Barolak <mbar@google.com>: Add an absl:: qualification to a usage of base_internal::SchedulingMode outside of an absl:: namespace. PiperOrigin-RevId: 200748234 -- a8d265290a22d629f3d9bf9f872c204200bfe8c8 by Mark Barolak <mbar@google.com>: Add a missing namespace closing comment to optional.h. PiperOrigin-RevId: 200739934 -- f05af8ee1c6b864dad2df7c907d424209a3e3202 by Abseil Team <absl-team@google.com>: Internal change PiperOrigin-RevId: 200719115 GitOrigin-RevId: f28d30df5769bb832dec3ff36d2fcd2bcdf494a3 Change-Id: Ie4fa601078fd4aa57286372611f1d114fdec82c0
2018-06-18 22:18:53 +02:00
// 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
//
// https://www.apache.org/licenses/LICENSE-2.0
-- f28d30df5769bb832dec3ff36d2fcd2bcdf494a3 by Shaindel Schwartz <shaindel@google.com>: Internal change PiperOrigin-RevId: 201046831 -- 711715a78b7e53dfaafd4d7f08a74e76db22af88 by Mark Barolak <mbar@google.com>: Internal fix PiperOrigin-RevId: 201043684 -- 64b53edd6bf1fa48f74e7f5d33f00f80d5089147 by Shaindel Schwartz <shaindel@google.com>: Remove extra whitespace PiperOrigin-RevId: 201041989 -- 0bdd2a0b33657b688e4a04aeba9ebba47e4dc6ca by Shaindel Schwartz <shaindel@google.com>: Whitespace fix. PiperOrigin-RevId: 201034413 -- 3deb0ac296ef1b74c4789e114a8a8bf53253f26b by Shaindel Schwartz <shaindel@google.com>: Scrub build tags. No functional changes. PiperOrigin-RevId: 201032927 -- da75d0f8b73baa7e8f4e9a092bba546012ed3b71 by Alex Strelnikov <strel@google.com>: Internal change. PiperOrigin-RevId: 201026131 -- 6815d80caa19870d0c441b6b9816c68db41393a5 by Tom Manshreck <shreck@google.com>: Add documentation for our LTS snapshot branches PiperOrigin-RevId: 201025191 -- 64c3b02006f39e6a8127bbabf9ec947fb45b6504 by Greg Falcon <gfalcon@google.com>: Provide absl::from_chars for double and float types. This is a forward-compatible implementation of std::from_chars from C++17. This provides exact "round_to_nearest" conversions, and has some nice properties: * Works with string_view (it can convert numbers from non-NUL-terminated buffers) * Never allocates memory * Faster than the standard library strtod() in our toolchain * Uses integer math in its calculations, so is unaffected by floating point environment * Unaffected by C locale Also change SimpleAtod/SimpleAtoi to use this new API under the hood. PiperOrigin-RevId: 201003324 -- 542869258eb100779497c899103dc96aced52749 by Greg Falcon <gfalcon@google.com>: Internal change PiperOrigin-RevId: 200999200 -- 3aba192775c7f80e2cd7f221b0a73537823c54ea by Gennadiy Rozental <rogeeff@google.com>: Internal change PiperOrigin-RevId: 200947470 -- daf9b9feedd748d5364a4c06165b7cb7604d3e1e by Mark Barolak <mbar@google.com>: Add an absl:: qualification to a usage of base_internal::SchedulingMode outside of an absl:: namespace. PiperOrigin-RevId: 200748234 -- a8d265290a22d629f3d9bf9f872c204200bfe8c8 by Mark Barolak <mbar@google.com>: Add a missing namespace closing comment to optional.h. PiperOrigin-RevId: 200739934 -- f05af8ee1c6b864dad2df7c907d424209a3e3202 by Abseil Team <absl-team@google.com>: Internal change PiperOrigin-RevId: 200719115 GitOrigin-RevId: f28d30df5769bb832dec3ff36d2fcd2bcdf494a3 Change-Id: Ie4fa601078fd4aa57286372611f1d114fdec82c0
2018-06-18 22:18:53 +02:00
//
// 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_