THUAI6/CAPI/cpp/grpc/include/absl/strings/charconv.h

// 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"

namespace absl
{
    ABSL_NAMESPACE_BEGIN

    // Workalike compatibilty 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
    {
        const char* ptr;
        std::errc ec;
    };

    // Workalike compatibilty 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(const char* first, const char* last,
                                       double& value,  // NOLINT
                                       chars_format fmt = chars_format::general);

    absl::from_chars_result from_chars(const char* first, 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_