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Simplify snprintf_float

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This commit is contained in:
Victor Zverovich 2022-05-21 12:34:21 -07:00
parent 440512f08d
commit f5cdf7cb04
1 changed files with 6 additions and 58 deletions
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64
include/fmt/format.h
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@ -1373,34 +1373,26 @@ FMT_API auto fmt_snprintf(char* buf, size_t size, const char* fmt, ...) -> int;
# define FMT_SNPRINTF fmt_snprintf
#endif // _MSC_VER
// Formats a floating-point number with snprintf.
// Formats a floating-point number with snprintf using the hexfloat format.
template <typename T>
auto snprintf_float(T value, int precision, float_specs specs,
buffer<char>& buf) -> int {
// Buffer capacity must be non-zero, otherwise MSVC's vsnprintf_s will fail.
FMT_ASSERT(buf.capacity() > buf.size(), "empty buffer");
FMT_ASSERT(specs.format == float_format::hex, "");
static_assert(!std::is_same<T, float>::value, "");
// Subtract 1 to account for the difference in precision since we use %e for
// both general and exponent format.
if (specs.format == float_format::general ||
specs.format == float_format::exp) {
precision = (precision >= 0 ? precision : 6) - 1;
}
// Build the format string.
char format[7]; // The longest format is "%#.*Le".
char* format_ptr = format;
*format_ptr++ = '%';
if (specs.showpoint && specs.format == float_format::hex) *format_ptr++ = '#';
if (specs.showpoint) *format_ptr++ = '#';
if (precision >= 0) {
*format_ptr++ = '.';
*format_ptr++ = '*';
}
if (std::is_same<T, long double>()) *format_ptr++ = 'L';
*format_ptr++ = specs.format != float_format::hex
? (specs.format == float_format::fixed ? 'f' : 'e')
: (specs.upper ? 'A' : 'a');
*format_ptr++ = specs.upper ? 'A' : 'a';
*format_ptr = '\0';
// Format using snprintf.
@ -1422,55 +1414,11 @@ auto snprintf_float(T value, int precision, float_specs specs,
}
auto size = to_unsigned(result);
// Size equal to capacity means that the last character was truncated.
if (size >= capacity) {
buf.try_reserve(size + offset + 1); // Add 1 for the terminating '\0'.
continue;
}
auto is_digit = [](char c) { return c >= '0' && c <= '9'; };
if (specs.format == float_format::fixed) {
if (precision == 0) {
buf.try_resize(size);
return 0;
}
// Find and remove the decimal point.
auto end = begin + size, p = end;
do {
--p;
} while (is_digit(*p));
int fraction_size = static_cast<int>(end - p - 1);
std::memmove(p, p + 1, to_unsigned(fraction_size));
buf.try_resize(size - 1);
return -fraction_size;
}
if (specs.format == float_format::hex) {
if (size < capacity) {
buf.try_resize(size + offset);
return 0;
}
// Find and parse the exponent.
auto end = begin + size, exp_pos = end;
do {
--exp_pos;
} while (*exp_pos != 'e');
char sign = exp_pos[1];
FMT_ASSERT(sign == '+' || sign == '-', "");
int exp = 0;
auto p = exp_pos + 2; // Skip 'e' and sign.
do {
FMT_ASSERT(is_digit(*p), "");
exp = exp * 10 + (*p++ - '0');
} while (p != end);
if (sign == '-') exp = -exp;
int fraction_size = 0;
if (exp_pos != begin + 1) {
// Remove trailing zeros.
auto fraction_end = exp_pos - 1;
while (*fraction_end == '0') --fraction_end;
// Move the fractional part left to get rid of the decimal point.
fraction_size = static_cast<int>(fraction_end - begin - 1);
std::memmove(begin + 1, begin + 2, to_unsigned(fraction_size));
}
buf.try_resize(to_unsigned(fraction_size) + offset + 1);
return exp - fraction_size;
buf.try_reserve(size + offset + 1); // Add 1 for the terminating '\0'.
}
}