spdlog/include/spdlog/fmt/chrono.h

105 lines
3.2 KiB
C++

//
// Copyright(c) 2016 Gabi Melman.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
//
#pragma once
#if defined(SPDLOG_USE_STD_FORMAT)
// Add a formatter for std::tm, since std::format only supports std::chrono
// taken from fmtlib
#include <cassert>
#include <ctime>
#include <format>
#include <string>
#include <string_view>
#include <type_traits>
#include <spdlog/common.h>
namespace spdlog::details
{
inline size_t strftime(char *str, size_t count, const char *format, const std::tm *time)
{
// Assign to a pointer to suppress GCCs -Wformat-nonliteral
// First assign the nullptr to suppress -Wsuggest-attribute=format
std::size_t (*strftime)(char*, std::size_t, const char*, const std::tm*) = nullptr;
strftime = std::strftime;
return strftime(str, count, format, time);
}
inline size_t strftime(wchar_t *str, size_t count, const wchar_t *format, const std::tm *time)
{
// See above
std::size_t (*wcsftime)(wchar_t*, std::size_t, const wchar_t*, const std::tm*) = nullptr;
wcsftime = std::wcsftime;
return wcsftime(str, count, format, time);
}
// Casts a nonnegative integer to unsigned.
template <typename Int>
SPDLOG_CONSTEXPR auto to_unsigned(Int value) -> typename std::make_unsigned<Int>::type
{
assert(value >= 0, "negative value");
return static_cast<typename std::make_unsigned<Int>::type>(value);
}
}
template <typename Char>
struct std::formatter<std::tm, Char>
{
template <typename ParseContext>
SPDLOG_CONSTEXPR_FUNC auto parse(ParseContext &ctx) -> decltype(ctx.begin())
{
auto it = ctx.begin();
if (it != ctx.end() && *it == ':') ++it;
auto end = it;
while (end != ctx.end() && *end != '}') ++end;
specs = {it, spdlog::details::to_unsigned(end - it)};
return end;
}
template <typename FormatContext>
auto format(const std::tm &tm, FormatContext &ctx) const -> decltype(ctx.out()) {
basic_string<Char> tm_format;
tm_format.append(specs);
// By appending an extra space we can distinguish an empty result that
// indicates insufficient buffer size from a guaranteed non-empty result
// https://github.com/fmtlib/fmt/issues/2238
tm_format.push_back(' ');
const size_t MIN_SIZE = 10;
basic_string<Char> buf;
buf.resize(MIN_SIZE);
for (;;)
{
size_t count = spdlog::details::strftime(buf.data(), buf.size(), tm_format.c_str(), &tm);
if (count != 0)
{
buf.resize(count);
break;
}
buf.resize(buf.size() * 2);
}
// Remove the extra space.
return std::copy(buf.begin(), buf.end() - 1, ctx.out());
}
basic_string_view<Char> specs;
};
#else
//
// include bundled or external copy of fmtlib's chrono support
//
# if !defined(SPDLOG_FMT_EXTERNAL)
# ifdef SPDLOG_HEADER_ONLY
# ifndef FMT_HEADER_ONLY
# define FMT_HEADER_ONLY
# endif
# endif
# include <spdlog/fmt/bundled/chrono.h>
# else
# include <fmt/chrono.h>
# endif
#endif