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Integrate Grisu

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This commit is contained in:
Victor Zverovich
2018-10-14 14:33:25 -07:00
parent 699297520a
commit 50b18a3c10
5 changed files with 201 additions and 195 deletions
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include/fmt/format.h
+27 -15
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@@ -289,15 +289,20 @@ inline bool use_grisu() {
return FMT_USE_GRISU && std::numeric_limits<double>::is_iec559;
}
struct grisu2_specs {
int precision;
char type;
uint_least8_t flags;
};
// Formats value using Grisu2 algorithm:
// https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf
template <typename Double>
FMT_API typename std::enable_if<sizeof(Double) == sizeof(uint64_t)>::type
grisu2_format(Double value, char *buffer, size_t &size, char type,
int precision, bool write_decimal_point);
FMT_API typename std::enable_if<sizeof(Double) == sizeof(uint64_t), bool>::type
grisu2_format(Double value, char *buffer, size_t &size, grisu2_specs);
template <typename Double>
inline typename std::enable_if<sizeof(Double) != sizeof(uint64_t)>::type
grisu2_format(Double, char *, size_t &, char, int, bool) {}
inline typename std::enable_if<sizeof(Double) != sizeof(uint64_t), bool>::type
grisu2_format(Double, char *, size_t &, grisu2_specs) { return false; }
template <typename Allocator>
typename Allocator::value_type *allocate(Allocator& alloc, std::size_t n) {
@@ -1203,13 +1208,13 @@ struct align_spec : empty_spec {
template <typename Char>
class basic_format_specs : public align_spec {
public:
unsigned flags_;
int precision_;
uint_least8_t flags_;
char type_;
FMT_CONSTEXPR basic_format_specs(
unsigned width = 0, char type = 0, wchar_t fill = ' ')
: align_spec(width, fill), flags_(0), precision_(-1), type_(type) {}
: align_spec(width, fill), precision_(-1), flags_(0), type_(type) {}
FMT_CONSTEXPR bool flag(unsigned f) const { return (flags_ & f) != 0; }
FMT_CONSTEXPR int precision() const { return precision_; }
@@ -2881,16 +2886,23 @@ void basic_writer<Range>::write_double(T value, const format_specs &spec) {
memory_buffer buffer;
char type = static_cast<char>(spec.type());
if (internal::const_check(
internal::use_grisu() && sizeof(T) <= sizeof(double)) &&
type != 'a' && type != 'A') {
bool use_grisu = internal::use_grisu() && sizeof(T) <= sizeof(double) &&
type != 'a' && type != 'A';
if (use_grisu) {
char buf[100]; // TODO: correct buffer size
size_t size = 0;
internal::grisu2_format(static_cast<double>(value), buf, size, type,
spec.precision(), spec.flag(HASH_FLAG));
FMT_ASSERT(size <= 100, "buffer overflow");
buffer.append(buf, buf + size); // TODO: avoid extra copy
} else {
auto gs = internal::grisu2_specs();
gs.type = type;
gs.precision = spec.precision();
gs.flags = spec.flags_;
use_grisu = internal::grisu2_format(
static_cast<double>(value), buf, size, gs);
if (use_grisu) {
FMT_ASSERT(size <= 100, "buffer overflow");
buffer.append(buf, buf + size); // TODO: avoid extra copy
}
}
if (!use_grisu) {
format_specs normalized_spec(spec);
normalized_spec.type_ = handler.type;
write_double_sprintf(value, normalized_spec, buffer);