|
||||
File indexing completed on 2025-01-18 09:27:24
0001 // Copyright 2018 The Abseil Authors. 0002 // 0003 // Licensed under the Apache License, Version 2.0 (the "License"); 0004 // you may not use this file except in compliance with the License. 0005 // You may obtain a copy of the License at 0006 // 0007 // https://www.apache.org/licenses/LICENSE-2.0 0008 // 0009 // Unless required by applicable law or agreed to in writing, software 0010 // distributed under the License is distributed on an "AS IS" BASIS, 0011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 0012 // See the License for the specific language governing permissions and 0013 // limitations under the License. 0014 0015 #ifndef ABSL_STRINGS_INTERNAL_CHARCONV_PARSE_H_ 0016 #define ABSL_STRINGS_INTERNAL_CHARCONV_PARSE_H_ 0017 0018 #include <cstdint> 0019 0020 #include "absl/base/config.h" 0021 #include "absl/strings/charconv.h" 0022 0023 namespace absl { 0024 ABSL_NAMESPACE_BEGIN 0025 namespace strings_internal { 0026 0027 // Enum indicating whether a parsed float is a number or special value. 0028 enum class FloatType { kNumber, kInfinity, kNan }; 0029 0030 // The decomposed parts of a parsed `float` or `double`. 0031 struct ParsedFloat { 0032 // Representation of the parsed mantissa, with the decimal point adjusted to 0033 // make it an integer. 0034 // 0035 // During decimal scanning, this contains 19 significant digits worth of 0036 // mantissa value. If digits beyond this point are found, they 0037 // are truncated, and if any of these dropped digits are nonzero, then 0038 // `mantissa` is inexact, and the full mantissa is stored in [subrange_begin, 0039 // subrange_end). 0040 // 0041 // During hexadecimal scanning, this contains 15 significant hex digits worth 0042 // of mantissa value. Digits beyond this point are sticky -- they are 0043 // truncated, but if any dropped digits are nonzero, the low bit of mantissa 0044 // will be set. (This allows for precise rounding, and avoids the need 0045 // to store the full mantissa in [subrange_begin, subrange_end).) 0046 uint64_t mantissa = 0; 0047 0048 // Floating point expontent. This reflects any decimal point adjustments and 0049 // any truncated digits from the mantissa. The absolute value of the parsed 0050 // number is represented by mantissa * (base ** exponent), where base==10 for 0051 // decimal floats, and base==2 for hexadecimal floats. 0052 int exponent = 0; 0053 0054 // The literal exponent value scanned from the input, or 0 if none was 0055 // present. This does not reflect any adjustments applied to mantissa. 0056 int literal_exponent = 0; 0057 0058 // The type of number scanned. 0059 FloatType type = FloatType::kNumber; 0060 0061 // When non-null, [subrange_begin, subrange_end) marks a range of characters 0062 // that require further processing. The meaning is dependent on float type. 0063 // If type == kNumber and this is set, this is a "wide input": the input 0064 // mantissa contained more than 19 digits. The range contains the full 0065 // mantissa. It plus `literal_exponent` need to be examined to find the best 0066 // floating point match. 0067 // If type == kNan and this is set, the range marks the contents of a 0068 // matched parenthesized character region after the NaN. 0069 const char* subrange_begin = nullptr; 0070 const char* subrange_end = nullptr; 0071 0072 // One-past-the-end of the successfully parsed region, or nullptr if no 0073 // matching pattern was found. 0074 const char* end = nullptr; 0075 }; 0076 0077 // Read the floating point number in the provided range, and populate 0078 // ParsedFloat accordingly. 0079 // 0080 // format_flags is a bitmask value specifying what patterns this API will match. 0081 // `scientific` and `fixed` are honored per std::from_chars rules 0082 // ([utility.from.chars], C++17): if exactly one of these bits is set, then an 0083 // exponent is required, or dislallowed, respectively. 0084 // 0085 // Template parameter `base` must be either 10 or 16. For base 16, a "0x" is 0086 // *not* consumed. The `hex` bit from format_flags is ignored by ParseFloat. 0087 template <int base> 0088 ParsedFloat ParseFloat(const char* begin, const char* end, 0089 absl::chars_format format_flags); 0090 0091 extern template ParsedFloat ParseFloat<10>(const char* begin, const char* end, 0092 absl::chars_format format_flags); 0093 extern template ParsedFloat ParseFloat<16>(const char* begin, const char* end, 0094 absl::chars_format format_flags); 0095 0096 } // namespace strings_internal 0097 ABSL_NAMESPACE_END 0098 } // namespace absl 0099 #endif // ABSL_STRINGS_INTERNAL_CHARCONV_PARSE_H_
[ Source navigation ] | [ Diff markup ] | [ Identifier search ] | [ general search ] |
This page was automatically generated by the 2.3.7 LXR engine. The LXR team |