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Optimize floating point formatting

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This commit is contained in:
Victor Zverovich 2020-10-09 14:06:24 -07:00
parent 3c13a88b14
commit bf19051a9f
1 changed files with 15 additions and 14 deletions
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29
include/fmt/format.h
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@ -1031,7 +1031,7 @@ template <typename Char> void copy2(Char* dst, const char* src) {
*dst++ = static_cast<Char>(*src++);
*dst = static_cast<Char>(*src);
}
inline void copy2(char* dst, const char* src) { memcpy(dst, src, 2); }
FMT_INLINE void copy2(char* dst, const char* src) { memcpy(dst, src, 2); }
template <typename Iterator> struct format_decimal_result {
Iterator begin;
@ -1764,7 +1764,10 @@ inline Char* write_significand(Char* out, UInt significand,
if (!decimal_point)
return format_decimal(out, significand, significand_size).end;
auto end = format_decimal(out + 1, significand, significand_size).end;
std::copy_n(out + 1, integral_size, out);
if (integral_size == 1)
out[0] = out[1];
else
std::copy_n(out + 1, integral_size, out);
out[integral_size] = decimal_point;
return end;
}
@ -1799,8 +1802,8 @@ OutputIt write_float(OutputIt out, const DecimalFP& fp,
auto significand = fp.significand;
int significand_size = get_significand_size(fp);
static const Char zero = static_cast<Char>('0');
char sign = data::signs[fspecs.sign];
int size = significand_size + (fspecs.sign ? 1 : 0);
auto sign = fspecs.sign;
int size = significand_size + (sign ? 1 : 0);
using iterator = remove_reference_t<decltype(reserve(out, 0))>;
int output_exp = fp.exponent + significand_size - 1;
@ -1816,21 +1819,19 @@ OutputIt write_float(OutputIt out, const DecimalFP& fp,
if (use_exp_format()) {
int num_zeros = 0;
if (fspecs.showpoint) {
num_zeros = fspecs.precision - significand_size;
if (num_zeros < 0) num_zeros = 0;
num_zeros = (std::max)(fspecs.precision - significand_size, 0);
size += num_zeros;
} else if (significand_size == 1) {
decimal_point = Char();
}
auto abs_output_exp = static_cast<unsigned>(output_exp);
if (output_exp < 0) abs_output_exp = 0 - abs_output_exp;
auto abs_output_exp = output_exp >= 0 ? output_exp : -output_exp;
int exp_digits = 2;
if (abs_output_exp >= 100) exp_digits = abs_output_exp >= 1000 ? 4 : 3;
size += (decimal_point ? 1 : 0) + num_zeros + 2 + exp_digits;
size += (decimal_point ? 1 : 0) + 2 + exp_digits;
char exp_char = fspecs.upper ? 'E' : 'e';
auto write = [=](iterator it) {
if (sign) *it++ = static_cast<Char>(sign);
if (sign) *it++ = static_cast<Char>(data::signs[sign]);
// Insert a decimal point after the first digit and add an exponent.
it = write_significand(it, significand, significand_size, 1,
decimal_point);
@ -1859,7 +1860,7 @@ OutputIt write_float(OutputIt out, const DecimalFP& fp,
}
return write_padded<align::right>(
out, specs, to_unsigned(size), [&](iterator it) {
if (sign) *it++ = static_cast<Char>(sign);
if (sign) *it++ = static_cast<Char>(data::signs[sign]);
it = write_significand<Char>(it, significand, significand_size);
it = std::fill_n(it, fp.exponent, zero);
if (!fspecs.showpoint) return it;
@ -1872,7 +1873,7 @@ OutputIt write_float(OutputIt out, const DecimalFP& fp,
size += 1 + (num_zeros > 0 ? num_zeros : 0);
return write_padded<align::right>(
out, specs, to_unsigned(size), [&](iterator it) {
if (sign) *it++ = static_cast<Char>(sign);
if (sign) *it++ = static_cast<Char>(data::signs[sign]);
it = write_significand(it, significand, significand_size, exp,
decimal_point);
return num_zeros > 0 ? std::fill_n(it, num_zeros, zero) : it;
@ -1887,7 +1888,7 @@ OutputIt write_float(OutputIt out, const DecimalFP& fp,
size += 2 + num_zeros;
return write_padded<align::right>(
out, specs, to_unsigned(size), [&](iterator it) {
if (sign) *it++ = static_cast<Char>(sign);
if (sign) *it++ = static_cast<Char>(data::signs[sign]);
*it++ = zero;
if (num_zeros == 0 && significand_size == 0 && !fspecs.showpoint)
return it;