Skip to content
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

Optimize %T in tm formatting #2500

Merged
merged 2 commits into from
Sep 15, 2021
Merged

Optimize %T in tm formatting #2500

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
20c68a6
Optimize %T in tm formatting
phprus Sep 13, 2021
7407f76
Fix wchar_t tm formatting
phprus Sep 13, 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
15 changes: 14 additions & 1 deletion include/fmt/chrono.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -549,6 +549,7 @@ template <typename Char> struct formatter<std::tm, Char> {
enum class spec {
unknown,
year_month_day,
hh_mm_ss,
};
spec spec_ = spec::unknown;

Expand All @@ -563,7 +564,13 @@ template <typename Char> struct formatter<std::tm, Char> {
while (end != ctx.end() && *end != '}') ++end;
auto size = detail::to_unsigned(end - it);
specs = {it, size};
if (specs == string_view("%F", 2)) spec_ = spec::year_month_day;
// basic_string_view<>::compare isn't constexpr before C++17
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There is no basic_string_view<> before C++17.

Could it be that the internal replacement should be updated?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Problem in std::char_traits<>::compare:

fmt/include/fmt/core.h

Lines 472 to 478 in 3d0c7ae

FMT_CONSTEXPR_CHAR_TRAITS auto compare(basic_string_view other) const -> int {
size_t str_size = size_ < other.size_ ? size_ : other.size_;
int result = std::char_traits<Char>::compare(data_, other.data_, str_size);
if (result == 0)
result = size_ == other.size_ ? 0 : (size_ < other.size_ ? -1 : 1);
return result;
}

constexpr std::char_traits<>::compare starts from C++17 only

if (specs.size() == 2 && specs[0] == Char('%')) {
if (specs[1] == Char('F'))
spec_ = spec::year_month_day;
else if (specs[1] == Char('T'))
spec_ = spec::hh_mm_ss;
}
return end;
}

Expand All @@ -578,6 +585,12 @@ template <typename Char> struct formatter<std::tm, Char> {
detail::to_unsigned(tm.tm_mon + 1),
detail::to_unsigned(tm.tm_mday), '-');
return std::copy_n(buf, sizeof(buf), ctx.out());
} else if (spec_ == spec::hh_mm_ss) {
char buf[8];
detail::write_digit2_separated(buf, detail::to_unsigned(tm.tm_hour),
detail::to_unsigned(tm.tm_min),
detail::to_unsigned(tm.tm_sec), ':');
return std::copy_n(buf, sizeof(buf), ctx.out());
}
basic_memory_buffer<Char> tm_format;
tm_format.append(specs.begin(), specs.end());
Expand Down
1 change: 1 addition & 0 deletions test/chrono-test.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,7 @@ TEST(chrono_test, format_tm) {
EXPECT_EQ(fmt::format("The date is {:%Y-%m-%d %H:%M:%S}.", tm),
"The date is 2016-04-25 11:22:33.");
EXPECT_EQ(fmt::format("{:%F}", tm), "2016-04-25");
EXPECT_EQ(fmt::format("{:%T}", tm), "11:22:33");
}

TEST(chrono_test, grow_buffer) {
Expand Down
2 changes: 2 additions & 0 deletions test/xchar-test.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -261,6 +261,8 @@ TEST(xchar_test, chrono) {
EXPECT_EQ(fmt::format("The date is {:%Y-%m-%d %H:%M:%S}.", tm),
"The date is 2016-04-25 11:22:33.");
EXPECT_EQ(L"42s", fmt::format(L"{}", std::chrono::seconds(42)));
EXPECT_EQ(fmt::format(L"{:%F}", tm), L"2016-04-25");
EXPECT_EQ(fmt::format(L"{:%T}", tm), L"11:22:33");
}

TEST(xchar_test, color) {
Expand Down