63e88f80
 Hu Chunming
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// Copyright (c) 2022 Dvir Yitzchaki.
// Use, modification and distribution are subject to the Boost Software License,
// Version 1.0. See http://www.boost.org/LICENSE_1_0.txt.
#ifndef BOOST_CONVERT_CHARCONV_BASED_CONVERTER_HPP
#define BOOST_CONVERT_CHARCONV_BASED_CONVERTER_HPP
#ifdef BOOST_NO_CXX17_HDR_CHARCONV
#error "This header requires <charconv> which is unavailable"
#endif // BOOST_NO_CXX17_HDR_CHARCONV
#ifdef BOOST_NO_CXX17_STRUCTURED_BINDINGS
#error "This header requires structured bindings which is unavailable"
#endif // BOOST_NO_CXX17_STRUCTURED_BINDINGS
#ifdef BOOST_NO_CXX17_IF_CONSTEXPR
#error "This header requires constexpr if which is unavailable"
#endif // BOOST_NO_CXX17_IF_CONSTEXPR
#include <boost/convert/base.hpp>
#include <charconv>
#include <type_traits>
namespace boost { namespace cnv { struct charconv; }}
/// @brief std::to/from_chars-based extended converter
/// @details The converter offers good overall performance and moderate formatting facilities.
struct boost::cnv::charconv : boost::cnv::cnvbase<boost::cnv::charconv>
{
using this_type = boost::cnv::charconv;
using base_type = boost::cnv::cnvbase<this_type>;
private:
friend struct boost::cnv::cnvbase<this_type>;
template<typename in_type>
cnv::range<char*>
to_str(in_type value_in, char* buf) const
{
const auto [ptr, ec] = [&]{
if constexpr (std::is_integral_v<in_type>) {
return std::to_chars(buf, buf + bufsize_, value_in, static_cast<int>(base_));
} else {
return std::to_chars(buf, buf + bufsize_, value_in, chars_format(), precision_);
}
}();
bool success = ec == std::errc{};
return cnv::range<char*>(buf, success ? ptr : buf);
}
template<typename string_type, typename out_type>
void
str_to(cnv::range<string_type> range, optional<out_type>& result_out) const
{
out_type result = boost::make_default<out_type>();
const auto [ptr, ec] = [&]{
if constexpr (std::is_integral_v<out_type>) {
return std::from_chars(&*range.begin(), &*range.end(), result, static_cast<int>(base_));
} else {
return std::from_chars(&*range.begin(), &*range.end(), result, chars_format());
}
}();
if (ec == std::errc{})
result_out = result;
}
std::chars_format chars_format() const
{
static constexpr std::chars_format format[] =
{
std::chars_format::fixed,
std::chars_format::scientific,
std::chars_format::hex
};
return format[int(notation_)];
}
std::chars_format fmt_ = std::chars_format::fixed;
};
#endif // BOOST_CONVERT_CHARCONV_BASED_CONVERTER_HPP
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