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Add support for extended precision FP

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This commit is contained in:
Victor Zverovich
2022-02-15 17:14:48 -08:00
parent c4c6b42de7
commit 161059dd98
2 changed files with 14 additions and 12 deletions
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23
include/fmt/format-inl.h
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@ -444,9 +444,6 @@ class bigint {
public: public:
FMT_CONSTEXPR20 bigint() : exp_(0) {} FMT_CONSTEXPR20 bigint() : exp_(0) {}
explicit bigint(uint64_t n) { assign(n); } explicit bigint(uint64_t n) { assign(n); }
FMT_CONSTEXPR20 ~bigint() {
FMT_ASSERT(bigits_.capacity() <= bigits_capacity, "");
}
bigint(const bigint&) = delete; bigint(const bigint&) = delete;
void operator=(const bigint&) = delete; void operator=(const bigint&) = delete;
@ -684,6 +681,14 @@ struct gen_digits_handler {
} }
}; };
inline FMT_CONSTEXPR20 void adjust_precision(int& precision, int exp10) {
// Adjust fixed precision by exponent because it is relative to decimal
// point.
if (exp10 > 0 && precision > max_value<int>() - exp10)
FMT_THROW(format_error("number is too big"));
precision += exp10;
}
// Generates output using the Grisu digit-gen algorithm. // Generates output using the Grisu digit-gen algorithm.
// error: the size of the region (lower, upper) outside of which numbers // error: the size of the region (lower, upper) outside of which numbers
// definitely do not round to value (Delta in Grisu3). // definitely do not round to value (Delta in Grisu3).
@ -701,14 +706,7 @@ FMT_INLINE FMT_CONSTEXPR20 digits::result grisu_gen_digits(
exp = count_digits(integral); // kappa in Grisu. exp = count_digits(integral); // kappa in Grisu.
// Non-fixed formats require at least one digit and no precision adjustment. // Non-fixed formats require at least one digit and no precision adjustment.
if (handler.fixed) { if (handler.fixed) {
// Adjust fixed precision by exponent because it is relative to decimal adjust_precision(handler.precision, exp + handler.exp10);
// point.
int precision_offset = exp + handler.exp10;
if (precision_offset > 0 &&
handler.precision > max_value<int>() - precision_offset) {
FMT_THROW(format_error("number is too big"));
}
handler.precision += precision_offset;
// Check if precision is satisfied just by leading zeros, e.g. // Check if precision is satisfied just by leading zeros, e.g.
// format("{:.2f}", 0.001) gives "0.00" without generating any digits. // format("{:.2f}", 0.001) gives "0.00" without generating any digits.
if (handler.precision <= 0) { if (handler.precision <= 0) {
@ -2277,6 +2275,9 @@ FMT_HEADER_ONLY_CONSTEXPR20 int format_float(Float value, int precision,
exp += handler.size - cached_exp10 - 1; exp += handler.size - cached_exp10 - 1;
precision = handler.precision; precision = handler.precision;
} }
} else {
exp = static_cast<int>(std::log10(value));
if (fixed) adjust_precision(precision, exp + 1);
} }
if (use_dragon) { if (use_dragon) {
auto f = fp(); auto f = fp();

3
include/fmt/format.h
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@ -2233,7 +2233,8 @@ FMT_CONSTEXPR20 auto write(OutputIt out, T value,
++precision; ++precision;
} }
if (const_check(std::is_same<T, float>())) fspecs.binary32 = true; if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
if (!is_fast_float<T>()) fspecs.fallback = true; if (!std::numeric_limits<T>::is_iec559 || std::numeric_limits<T>::digits > 64)
fspecs.fallback = true;
int exp = format_float(convert_float(value), precision, fspecs, buffer); int exp = format_float(convert_float(value), precision, fspecs, buffer);
fspecs.precision = precision; fspecs.precision = precision;
auto fp = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp}; auto fp = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp};