1 // Copyright 2018 The Abseil Authors.
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
7 // https://www.apache.org/licenses/LICENSE-2.0
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.
15 #ifndef ABSL_STRINGS_CHARCONV_H_
16 #define ABSL_STRINGS_CHARCONV_H_
18 #include <system_error> // NOLINT(build/c++11)
22 // Workalike compatibilty version of std::chars_format from C++17.
24 // This is an bitfield enumerator which can be passed to absl::from_chars to
25 // configure the string-to-float conversion.
26 enum class chars_format {
30 general = fixed | scientific,
33 // The return result of a string-to-number conversion.
35 // `ec` will be set to `invalid_argument` if a well-formed number was not found
36 // at the start of the input range, `result_out_of_range` if a well-formed
37 // number was found, but it was out of the representable range of the requested
38 // type, or to std::errc() otherwise.
40 // If a well-formed number was found, `ptr` is set to one past the sequence of
41 // characters that were successfully parsed. If none was found, `ptr` is set
42 // to the `first` argument to from_chars.
43 struct from_chars_result {
48 // Workalike compatibilty version of std::from_chars from C++17. Currently
49 // this only supports the `double` and `float` types.
51 // This interface incorporates the proposed resolutions for library issues
52 // DR 3080 and DR 3081. If these are adopted with different wording,
53 // Abseil's behavior will change to match the standard. (The behavior most
54 // likely to change is for DR 3081, which says what `value` will be set to in
55 // the case of overflow and underflow. Code that wants to avoid possible
56 // breaking changes in this area should not depend on `value` when the returned
57 // from_chars_result indicates a range error.)
59 // Searches the range [first, last) for the longest matching pattern beginning
60 // at `first` that represents a floating point number. If one is found, store
61 // the result in `value`.
63 // The matching pattern format is almost the same as that of strtod(), except
64 // that C locale is not respected, and an initial '+' character in the input
65 // range will never be matched.
67 // If `fmt` is set, it must be one of the enumerator values of the chars_format.
68 // (This is despite the fact that chars_format is a bitmask type.) If set to
69 // `scientific`, a matching number must contain an exponent. If set to `fixed`,
70 // then an exponent will never match. (For example, the string "1e5" will be
71 // parsed as "1".) If set to `hex`, then a hexadecimal float is parsed in the
72 // format that strtod() accepts, except that a "0x" prefix is NOT matched.
73 // (In particular, in `hex` mode, the input "0xff" results in the largest
74 // matching pattern "0".)
75 absl::from_chars_result from_chars(const char* first, const char* last,
76 double& value, // NOLINT
77 chars_format fmt = chars_format::general);
79 absl::from_chars_result from_chars(const char* first, const char* last,
80 float& value, // NOLINT
81 chars_format fmt = chars_format::general);
83 // std::chars_format is specified as a bitmask type, which means the following
84 // operations must be provided:
85 inline constexpr chars_format operator&(chars_format lhs, chars_format rhs) {
86 return static_cast<chars_format>(static_cast<int>(lhs) &
87 static_cast<int>(rhs));
89 inline constexpr chars_format operator|(chars_format lhs, chars_format rhs) {
90 return static_cast<chars_format>(static_cast<int>(lhs) |
91 static_cast<int>(rhs));
93 inline constexpr chars_format operator^(chars_format lhs, chars_format rhs) {
94 return static_cast<chars_format>(static_cast<int>(lhs) ^
95 static_cast<int>(rhs));
97 inline constexpr chars_format operator~(chars_format arg) {
98 return static_cast<chars_format>(~static_cast<int>(arg));
100 inline chars_format& operator&=(chars_format& lhs, chars_format rhs) {
104 inline chars_format& operator|=(chars_format& lhs, chars_format rhs) {
108 inline chars_format& operator^=(chars_format& lhs, chars_format rhs) {
115 #endif // ABSL_STRINGS_CHARCONV_H_