| // 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 | |
| // | |
| // 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. | |
| namespace absl { | |
| ABSL_NAMESPACE_BEGIN | |
| 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 | |
| ABSL_NAMESPACE_END | |
| } // namespace absl | |