// 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_