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 // 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"
 #include "absl/base/nullability.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
 // Workalike compatibility 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 {
   absl::Nonnull<const char*> ptr;
   std::errc ec;
 };
 
 // Workalike compatibility 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(absl::Nonnull<const char*> first,
                                    absl::Nonnull<const char*> last,
                                    double& value,  // NOLINT
                                    chars_format fmt = chars_format::general);
 
 absl::from_chars_result from_chars(absl::Nonnull<const char*> first,
                                    absl::Nonnull<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_

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