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Partially implement Grisu3

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This commit is contained in:
Victor Zverovich
2019-04-27 06:52:46 -07:00
parent 40a7975640
commit 8d8ea21c69
4 changed files with 81 additions and 37 deletions
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29
include/fmt/format.h
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@@ -1124,13 +1124,19 @@ FMT_CONSTEXPR unsigned basic_parse_context<Char, ErrorHandler>::next_arg_id() {
namespace internal {
// Formats value using Grisu2 algorithm:
namespace grisu_options {
enum {
fixed = 1,
grisu3 = 2
};
}
// Formats value using the Grisu algorithm:
// https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf
template <typename Double, FMT_ENABLE_IF(sizeof(Double) == sizeof(uint64_t))>
FMT_API bool grisu2_format(Double value, buffer<char>& buf, int precision,
bool fixed, int& exp);
FMT_API bool grisu_format(Double, buffer<char>&, int, unsigned, int&);
template <typename Double, FMT_ENABLE_IF(sizeof(Double) != sizeof(uint64_t))>
inline bool grisu2_format(Double, buffer<char>&, int, bool, int&) {
inline bool grisu_format(Double, buffer<char>&, int, unsigned, int&) {
return false;
}
@@ -1166,8 +1172,8 @@ template <typename Char, typename It> It write_exponent(int exp, It it) {
// The number is given as v = digits * pow(10, exp).
template <typename Char, typename It>
It grisu2_prettify(const char* digits, int size, int exp, It it,
gen_digits_params params) {
It grisu_prettify(const char* digits, int size, int exp, It it,
gen_digits_params params) {
// pow(10, full_exp - 1) <= v <= pow(10, full_exp).
int full_exp = size + exp;
if (!params.fixed) {
@@ -2663,7 +2669,7 @@ template <typename Range> class basic_writer {
int full_exp = num_digits + exp - 1;
int precision = params.num_digits > 0 ? params.num_digits : 11;
params_.fixed |= full_exp >= -4 && full_exp < precision;
auto it = internal::grisu2_prettify<char>(
auto it = internal::grisu_prettify<char>(
digits.data(), num_digits, exp, internal::counting_iterator<char>(),
params_);
size_ = it.count();
@@ -2675,8 +2681,8 @@ template <typename Range> class basic_writer {
template <typename It> void operator()(It&& it) {
if (sign_) *it++ = static_cast<char_type>(sign_);
int num_digits = static_cast<int>(digits_.size());
it = internal::grisu2_prettify<char_type>(digits_.data(), num_digits,
exp_, it, params_);
it = internal::grisu_prettify<char_type>(digits_.data(), num_digits, exp_,
it, params_);
}
};
@@ -2876,11 +2882,12 @@ void basic_writer<Range>::write_double(T value, const format_specs& spec) {
memory_buffer buffer;
int exp = 0;
int precision = spec.has_precision() || !spec.type ? spec.precision : 6;
unsigned options = handler.fixed ? internal::grisu_options::fixed : 0;
bool use_grisu = fmt::internal::use_grisu<T>() &&
(spec.type != 'a' && spec.type != 'A' && spec.type != 'e' &&
spec.type != 'E') &&
internal::grisu2_format(static_cast<double>(value), buffer,
precision, handler.fixed, exp);
internal::grisu_format(static_cast<double>(value), buffer,
precision, options, exp);
if (!use_grisu) internal::sprintf_format(value, buffer, spec);
if (handler.as_percentage) {