121 lines
4.8 KiB
C++
121 lines
4.8 KiB
C++
// Copyright 2018 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_STRINGS_CHARCONV_H_
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#define ABSL_STRINGS_CHARCONV_H_
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#include <system_error> // NOLINT(build/c++11)
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#include "absl/base/config.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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// Workalike compatibilty version of std::chars_format from C++17.
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//
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// This is an bitfield enumerator which can be passed to absl::from_chars to
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// configure the string-to-float conversion.
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enum class chars_format {
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scientific = 1,
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fixed = 2,
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hex = 4,
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general = fixed | scientific,
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};
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// The return result of a string-to-number conversion.
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//
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// `ec` will be set to `invalid_argument` if a well-formed number was not found
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// at the start of the input range, `result_out_of_range` if a well-formed
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// number was found, but it was out of the representable range of the requested
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// type, or to std::errc() otherwise.
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//
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// If a well-formed number was found, `ptr` is set to one past the sequence of
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// characters that were successfully parsed. If none was found, `ptr` is set
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// to the `first` argument to from_chars.
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struct from_chars_result {
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const char* ptr;
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std::errc ec;
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};
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// Workalike compatibilty version of std::from_chars from C++17. Currently
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// this only supports the `double` and `float` types.
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//
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// This interface incorporates the proposed resolutions for library issues
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// DR 3080 and DR 3081. If these are adopted with different wording,
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// Abseil's behavior will change to match the standard. (The behavior most
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// likely to change is for DR 3081, which says what `value` will be set to in
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// the case of overflow and underflow. Code that wants to avoid possible
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// breaking changes in this area should not depend on `value` when the returned
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// from_chars_result indicates a range error.)
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//
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// Searches the range [first, last) for the longest matching pattern beginning
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// at `first` that represents a floating point number. If one is found, store
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// the result in `value`.
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//
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// The matching pattern format is almost the same as that of strtod(), except
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// that (1) C locale is not respected, (2) an initial '+' character in the
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// input range will never be matched, and (3) leading whitespaces are not
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// ignored.
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//
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// If `fmt` is set, it must be one of the enumerator values of the chars_format.
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// (This is despite the fact that chars_format is a bitmask type.) If set to
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// `scientific`, a matching number must contain an exponent. If set to `fixed`,
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// then an exponent will never match. (For example, the string "1e5" will be
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// parsed as "1".) If set to `hex`, then a hexadecimal float is parsed in the
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// format that strtod() accepts, except that a "0x" prefix is NOT matched.
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// (In particular, in `hex` mode, the input "0xff" results in the largest
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// matching pattern "0".)
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absl::from_chars_result from_chars(const char* first, const char* last,
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double& value, // NOLINT
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chars_format fmt = chars_format::general);
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absl::from_chars_result from_chars(const char* first, const char* last,
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float& value, // NOLINT
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chars_format fmt = chars_format::general);
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// std::chars_format is specified as a bitmask type, which means the following
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// operations must be provided:
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inline constexpr chars_format operator&(chars_format lhs, chars_format rhs) {
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return static_cast<chars_format>(static_cast<int>(lhs) &
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static_cast<int>(rhs));
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}
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inline constexpr chars_format operator|(chars_format lhs, chars_format rhs) {
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return static_cast<chars_format>(static_cast<int>(lhs) |
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static_cast<int>(rhs));
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}
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inline constexpr chars_format operator^(chars_format lhs, chars_format rhs) {
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return static_cast<chars_format>(static_cast<int>(lhs) ^
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static_cast<int>(rhs));
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}
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inline constexpr chars_format operator~(chars_format arg) {
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return static_cast<chars_format>(~static_cast<int>(arg));
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}
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inline chars_format& operator&=(chars_format& lhs, chars_format rhs) {
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lhs = lhs & rhs;
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return lhs;
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}
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inline chars_format& operator|=(chars_format& lhs, chars_format rhs) {
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lhs = lhs | rhs;
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return lhs;
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}
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inline chars_format& operator^=(chars_format& lhs, chars_format rhs) {
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lhs = lhs ^ rhs;
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return lhs;
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}
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_STRINGS_CHARCONV_H_
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