from_chars.hpp

Go to the documentation of this file.

// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2019 Tobias Hienzsch
 
#ifndef TETL_CHARCONV_FROM_CHARS_HPP
#define TETL_CHARCONV_FROM_CHARS_HPP
 
#include <etl/_concepts/integral.hpp>
#include <etl/_concepts/same_as.hpp>
#include <etl/_cstddef/size_t.hpp>
#include <etl/_strings/to_integer.hpp>
#include <etl/_system_error/errc.hpp>
 
namespace etl {
 
/// \brief Primitive numerical input conversion
struct from_chars_result {
    char const* ptr{nullptr};
    etl::errc ec{};
 
    [[nodiscard]] constexpr explicit operator bool() const noexcept
    {
        return ec == etl::errc{};
    }
 
    friend auto operator==(from_chars_result const&, from_chars_result const&) -> bool = default;
};
 
/// \brief Analyzes the character sequence [first,last) for a pattern described
/// below. If no characters match the pattern or if the value obtained by
/// parsing the matched characters is not representable in the type of value,
/// value is unmodified, otherwise the characters matching the pattern are
/// interpreted as a text representation of an arithmetic value, which is stored
/// in value.
template <integral Int>
    requires(not same_as<Int, bool>)
[[nodiscard]] constexpr auto from_chars(char const* first, char const* last, Int& value, int base = 10)
    -> from_chars_result
{
    constexpr auto options     = strings::to_integer_options{.skip_whitespace = false, .check_overflow = true};
    auto const [end, err, val] = strings::to_integer<Int, options>({first, last}, static_cast<Int>(base));
 
    if (err == strings::to_integer_error::overflow) {
        return from_chars_result{.ptr = end, .ec = errc::result_out_of_range};
    }
    if (err == strings::to_integer_error::invalid_input) {
        return from_chars_result{.ptr = end, .ec = errc::invalid_argument};
    }
 
    value = val;
    return from_chars_result{.ptr = end, .ec = {}};
}
 
} // namespace etl
 
#endif // TETL_CHARCONV_FROM_CHARS_HPP