Skip to content

Simplifying format_decimal() #2498

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
vitaut merged 2 commits into from
Sep 12, 2021
Merged

Simplifying format_decimal() #2498

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
8c5c428
Add copy2() constexpr
Roman-Koshelev Sep 12, 2021
9052207
Removed redundant format_decimal implementation for constexpr context
Roman-Koshelev Sep 12, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 12 additions & 12 deletions include/fmt/format.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1049,11 +1049,19 @@ inline auto equal2(const char* lhs, const char* rhs) -> bool {
}

// Copies two characters from src to dst.
template <typename Char> void copy2(Char* dst, const char* src) {
*dst++ = static_cast<Char>(*src++);
*dst = static_cast<Char>(*src);
template <typename Char>
FMT_CONSTEXPR20 FMT_INLINE void copy2(Char* dst, const char* src) {
if (!is_constant_evaluated() && std::is_same<Char, char>::value) {
memcpy(dst, src, 2);
} else {
// We read both bytes before writing so that the compiler can do it in
// one pair of read/write instructions (even if Char aliases char)
char dc0 = *src++;
char dc1 = *src;
*dst++ = static_cast<Char>(dc0);
*dst = static_cast<Char>(dc1);
}
}
FMT_INLINE void copy2(char* dst, const char* src) { memcpy(dst, src, 2); }

template <typename Iterator> struct format_decimal_result {
Iterator begin;
Expand All @@ -1069,14 +1077,6 @@ FMT_CONSTEXPR20 auto format_decimal(Char* out, UInt value, int size)
FMT_ASSERT(size >= count_digits(value), "invalid digit count");
out += size;
Char* end = out;
if (is_constant_evaluated()) {
while (value >= 10) {
*--out = static_cast<Char>('0' + value % 10);
value /= 10;
}
*--out = static_cast<Char>('0' + value);
return {out, end};
}
while (value >= 100) {
// Integer division is slow so do it for a group of two digits instead
// of for every digit. The idea comes from the talk by Alexandrescu
Expand Down