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Support C++20 std::format as an alternative to fmtlib

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This commit is contained in:
Charless Milette
2021-11-13 11:29:05 -05:00
parent ff9313e6dd
commit 44a4517e2b
34 changed files with 445 additions and 143 deletions
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54
include/spdlog/details/fmt_helper.h
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@@ -8,6 +8,11 @@
#include <spdlog/fmt/fmt.h>
#include <spdlog/common.h>
#ifdef SPDLOG_USE_STD_FORMAT
#include <charconv>
#include <limits>
#endif
// Some fmt helpers to efficiently format and pad ints and strings
namespace spdlog {
namespace details {
@@ -24,17 +29,63 @@ inline void append_string_view(spdlog::string_view_t view, memory_buf_t &dest)
dest.append(buf_ptr, buf_ptr + view.size());
}
#ifdef SPDLOG_USE_STD_FORMAT
template<typename T>
inline void append_int(T n, memory_buf_t &dest)
{
// Buffer should be large enough to hold all digits (digits10 + 1) and a sign
SPDLOG_CONSTEXPR auto BUF_SIZE = std::numeric_limits<T>::digits10 + 2;
char buf[BUF_SIZE];
auto [ptr, ec] = std::to_chars(buf, buf + BUF_SIZE, n, 10);
if (ec == std::errc())
{
dest.append(buf, ptr);
}
else
{
throw_spdlog_ex("Failed to format int", static_cast<int>(ec));
}
}
#else
template<typename T>
inline void append_int(T n, memory_buf_t &dest)
{
fmt::format_int i(n);
dest.append(i.data(), i.data() + i.size());
}
#endif
template<typename T>
SPDLOG_CONSTEXPR unsigned int count_digits_fallback(T n)
{
// taken from fmt.
unsigned int count = 1;
for (;;)
{
// Integer division is slow so do it for a group of four digits instead
// of for every digit. The idea comes from the talk by Alexandrescu
// "Three Optimization Tips for C++". See speed-test for a comparison.
if (n < 10)
return count;
if (n < 100)
return count + 1;
if (n < 1000)
return count + 2;
if (n < 10000)
return count + 3;
n /= 10000u;
count += 4;
}
}
template<typename T>
inline unsigned int count_digits(T n)
{
using count_type = typename std::conditional<(sizeof(T) > sizeof(uint32_t)), uint64_t, uint32_t>::type;
#ifdef SPDLOG_USE_STD_FORMAT
return count_digits_fallback(static_cast<count_type>(n));
#else
return static_cast<unsigned int>(fmt::
// fmt 7.0.0 renamed the internal namespace to detail.
// See: https://github.com/fmtlib/fmt/issues/1538
@@ -44,6 +95,7 @@ inline unsigned int count_digits(T n)
detail
#endif
::count_digits(static_cast<count_type>(n)));
#endif
}
inline void pad2(int n, memory_buf_t &dest)
@@ -55,7 +107,7 @@ inline void pad2(int n, memory_buf_t &dest)
}
else // unlikely, but just in case, let fmt deal with it
{
fmt::format_to(std::back_inserter(dest), SPDLOG_FMT_RUNTIME("{:02}"), n);
fmt_lib::format_to(std::back_inserter(dest), "{:02}", n);
}
}