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Optimize default fast-float fixed presentation

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This commit is contained in:
Xlqmu 2026-03-09 09:29:04 +08:00
parent 314e8c7f8b
commit d8a6a42e56
1 changed files with 35 additions and 0 deletions
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35
include/fmt/format.h
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@ -2528,6 +2528,26 @@ inline auto write_exponent_significand(Char* out, UInt significand,
return out;
}
template <typename Char, typename UInt,
FMT_ENABLE_IF(std::is_integral<UInt>::value)>
inline auto write_default_fp(Char* out, UInt significand, int significand_size,
int decimal_exponent, sign s) -> Char* {
if (s != sign::none) *out++ = Char('-');
int exp = decimal_exponent + significand_size;
if (decimal_exponent >= 0) {
out = write_significand<Char>(out, significand, significand_size);
return detail::fill_n(out, decimal_exponent, Char('0'));
}
if (exp > 0) {
return write_significand(out, significand, significand_size, exp,
Char('.'));
}
*out++ = Char('0');
*out++ = Char('.');
out = detail::fill_n(out, -exp, Char('0'));
return write_significand<Char>(out, significand, significand_size);
}
template <typename OutputIt, typename Char>
FMT_CONSTEXPR auto write_significand(OutputIt out, const char* significand,
int significand_size, int integral_size,
@ -3605,6 +3625,21 @@ FMT_CONSTEXPR20 auto write(OutputIt out, T value) -> OutputIt {
int significand_size = count_digits(significand);
int exponent = dec.exponent + significand_size - 1;
if (use_fixed(exponent, detail::exp_upper<T>())) {
size_t size = std::is_pointer<OutputIt>::value
? 0u
: to_unsigned((s != sign::none ? 1 : 0) +
(dec.exponent >= 0
? significand_size + dec.exponent
: exponent >= 0
? significand_size + 1
: significand_size + 2 -
(dec.exponent +
significand_size)));
if (auto ptr = to_pointer<Char>(out, size)) {
ptr = write_default_fp(ptr, significand, significand_size, dec.exponent,
s);
return select<std::is_pointer<OutputIt>::value>(ptr, out);
}
return write_fixed<Char, fallback_digit_grouping<Char>>(
out, dec, significand_size, Char('.'), {}, s);
}