// 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. #ifndef ABSL_STRINGS_CHARCONV_H_ #define ABSL_STRINGS_CHARCONV_H_ #include <system_error> // NOLINT(build/c++11) #include "absl/base/config.h" namespace absl { ABSL_NAMESPACE_BEGIN // Workalike compatibilty version of std::chars_format from C++17. // // This is an bitfield enumerator which can be passed to absl::from_chars to // configure the string-to-float conversion. enum class chars_format { scientific = 1, fixed = 2, hex = 4, general = fixed | scientific, }; // The return result of a string-to-number conversion. // // `ec` will be set to `invalid_argument` if a well-formed number was not found // at the start of the input range, `result_out_of_range` if a well-formed // number was found, but it was out of the representable range of the requested // type, or to std::errc() otherwise. // // If a well-formed number was found, `ptr` is set to one past the sequence of // characters that were successfully parsed. If none was found, `ptr` is set // to the `first` argument to from_chars. struct from_chars_result { const char* ptr; std::errc ec; }; // Workalike compatibilty version of std::from_chars from C++17. Currently // this only supports the `double` and `float` types. // // This interface incorporates the proposed resolutions for library issues // DR 3080 and DR 3081. If these are adopted with different wording, // Abseil's behavior will change to match the standard. (The behavior most // likely to change is for DR 3081, which says what `value` will be set to in // the case of overflow and underflow. Code that wants to avoid possible // breaking changes in this area should not depend on `value` when the returned // from_chars_result indicates a range error.) // // Searches the range [first, last) for the longest matching pattern beginning // at `first` that represents a floating point number. If one is found, store // the result in `value`. // // The matching pattern format is almost the same as that of strtod(), except // that (1) C locale is not respected, (2) an initial '+' character in the // input range will never be matched, and (3) leading whitespaces are not // ignored. // // If `fmt` is set, it must be one of the enumerator values of the chars_format. // (This is despite the fact that chars_format is a bitmask type.) If set to // `scientific`, a matching number must contain an exponent. If set to `fixed`, // then an exponent will never match. (For example, the string "1e5" will be // parsed as "1".) If set to `hex`, then a hexadecimal float is parsed in the // format that strtod() accepts, except that a "0x" prefix is NOT matched. // (In particular, in `hex` mode, the input "0xff" results in the largest // matching pattern "0".) absl::from_chars_result from_chars(const char* first, const char* last, double& value, // NOLINT chars_format fmt = chars_format::general); absl::from_chars_result from_chars(const char* first, const char* last, float& value, // NOLINT chars_format fmt = chars_format::general); // std::chars_format is specified as a bitmask type, which means the following // operations must be provided: inline constexpr chars_format operator&(chars_format lhs, chars_format rhs) { return static_cast<chars_format>(static_cast<int>(lhs) & static_cast<int>(rhs)); } inline constexpr chars_format operator|(chars_format lhs, chars_format rhs) { return static_cast<chars_format>(static_cast<int>(lhs) | static_cast<int>(rhs)); } inline constexpr chars_format operator^(chars_format lhs, chars_format rhs) { return static_cast<chars_format>(static_cast<int>(lhs) ^ static_cast<int>(rhs)); } inline constexpr chars_format operator~(chars_format arg) { return static_cast<chars_format>(~static_cast<int>(arg)); } inline chars_format& operator&=(chars_format& lhs, chars_format rhs) { lhs = lhs & rhs; return lhs; } inline chars_format& operator|=(chars_format& lhs, chars_format rhs) { lhs = lhs | rhs; return lhs; } inline chars_format& operator^=(chars_format& lhs, chars_format rhs) { lhs = lhs ^ rhs; return lhs; } ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_STRINGS_CHARCONV_H_