1 // Copyright 2018 The Abseil Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef ABSL_STRINGS_CHARCONV_H_ 16 #define ABSL_STRINGS_CHARCONV_H_ 17 18 #include <system_error> // NOLINT(build/c++11) 19 20 #include "absl/base/config.h" 21 #include "absl/base/nullability.h" 22 23 namespace absl { 24 ABSL_NAMESPACE_BEGIN 25 26 // Workalike compatibility version of std::chars_format from C++17. 27 // 28 // This is an bitfield enumerator which can be passed to absl::from_chars to 29 // configure the string-to-float conversion. 30 enum class chars_format { 31 scientific = 1, 32 fixed = 2, 33 hex = 4, 34 general = fixed | scientific, 35 }; 36 37 // The return result of a string-to-number conversion. 38 // 39 // `ec` will be set to `invalid_argument` if a well-formed number was not found 40 // at the start of the input range, `result_out_of_range` if a well-formed 41 // number was found, but it was out of the representable range of the requested 42 // type, or to std::errc() otherwise. 43 // 44 // If a well-formed number was found, `ptr` is set to one past the sequence of 45 // characters that were successfully parsed. If none was found, `ptr` is set 46 // to the `first` argument to from_chars. 47 struct from_chars_result { 48 absl::Nonnull<const char*> ptr; 49 std::errc ec; 50 }; 51 52 // Workalike compatibility version of std::from_chars from C++17. Currently 53 // this only supports the `double` and `float` types. 54 // 55 // This interface incorporates the proposed resolutions for library issues 56 // DR 3080 and DR 3081. If these are adopted with different wording, 57 // Abseil's behavior will change to match the standard. (The behavior most 58 // likely to change is for DR 3081, which says what `value` will be set to in 59 // the case of overflow and underflow. Code that wants to avoid possible 60 // breaking changes in this area should not depend on `value` when the returned 61 // from_chars_result indicates a range error.) 62 // 63 // Searches the range [first, last) for the longest matching pattern beginning 64 // at `first` that represents a floating point number. If one is found, store 65 // the result in `value`. 66 // 67 // The matching pattern format is almost the same as that of strtod(), except 68 // that (1) C locale is not respected, (2) an initial '+' character in the 69 // input range will never be matched, and (3) leading whitespaces are not 70 // ignored. 71 // 72 // If `fmt` is set, it must be one of the enumerator values of the chars_format. 73 // (This is despite the fact that chars_format is a bitmask type.) If set to 74 // `scientific`, a matching number must contain an exponent. If set to `fixed`, 75 // then an exponent will never match. (For example, the string "1e5" will be 76 // parsed as "1".) If set to `hex`, then a hexadecimal float is parsed in the 77 // format that strtod() accepts, except that a "0x" prefix is NOT matched. 78 // (In particular, in `hex` mode, the input "0xff" results in the largest 79 // matching pattern "0".) 80 absl::from_chars_result from_chars(absl::Nonnull<const char*> first, 81 absl::Nonnull<const char*> last, 82 double& value, // NOLINT 83 chars_format fmt = chars_format::general); 84 85 absl::from_chars_result from_chars(absl::Nonnull<const char*> first, 86 absl::Nonnull<const char*> last, 87 float& value, // NOLINT 88 chars_format fmt = chars_format::general); 89 90 // std::chars_format is specified as a bitmask type, which means the following 91 // operations must be provided: 92 inline constexpr chars_format operator&(chars_format lhs, chars_format rhs) { 93 return static_cast<chars_format>(static_cast<int>(lhs) & 94 static_cast<int>(rhs)); 95 } 96 inline constexpr chars_format operator|(chars_format lhs, chars_format rhs) { 97 return static_cast<chars_format>(static_cast<int>(lhs) | 98 static_cast<int>(rhs)); 99 } 100 inline constexpr chars_format operator^(chars_format lhs, chars_format rhs) { 101 return static_cast<chars_format>(static_cast<int>(lhs) ^ 102 static_cast<int>(rhs)); 103 } 104 inline constexpr chars_format operator~(chars_format arg) { 105 return static_cast<chars_format>(~static_cast<int>(arg)); 106 } 107 inline chars_format& operator&=(chars_format& lhs, chars_format rhs) { 108 lhs = lhs & rhs; 109 return lhs; 110 } 111 inline chars_format& operator|=(chars_format& lhs, chars_format rhs) { 112 lhs = lhs | rhs; 113 return lhs; 114 } 115 inline chars_format& operator^=(chars_format& lhs, chars_format rhs) { 116 lhs = lhs ^ rhs; 117 return lhs; 118 } 119 120 ABSL_NAMESPACE_END 121 } // namespace absl 122 123 #endif // ABSL_STRINGS_CHARCONV_H_ 124