Add precision modifier for seconds in chrono format #3148
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Could you copy the summary (updating it if needed) from #3122? |
include/fmt/chrono.h
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| return; | ||
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| FMT_ASSERT(std::is_floating_point<typename Duration::rep>::value, ""); |
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Let's add an alias for typename Duration::rep and use it here and in several places below.
include/fmt/chrono.h
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| @@ -1056,31 +1056,91 @@ void write_fractional_seconds(OutputIt& out, Duration d) { | |||
| } | |||
| } | |||
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| template <typename Char, typename OutputIt, typename Duration> | |||
| void write_fractional_seconds(OutputIt& out, Duration d, int precision) { | |||
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Let's merge this overload with the one above to reduce code duplication.
include/fmt/chrono.h
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| : std::chrono::duration_cast<subsecond_precision>(fractional) | ||
| .count(); | ||
| uint32_or_64_or_128_t<long long> n = | ||
| to_unsigned(to_nonnegative_int(subseconds, max_value<long long>())); |
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Can subseconds be negative?
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It's nonnegative because fractional is nonnegative:
const auto fractional = detail::abs(d) - std::chrono::duration_cast<std::chrono::seconds>(d);But subseconds can be signed or unsigned and to_unsigned raises error if argument is unsigned, so i'll make static_cast.
include/fmt/chrono.h
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| // Format subseconds which are given as a floating point type with an appropiate | ||
| // number of digits. We cannot pass the Duration here, as we explicitly need to | ||
| // pass the Rep value in the chrono_formatter. | ||
| template <typename Duration> | ||
| void write_floating_seconds(memory_buffer& buf, Duration duration) { | ||
| FMT_ASSERT(std::is_floating_point<typename Duration::rep>::value, ""); | ||
| using Rep = typename Duration::rep; |
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nit: Rep -> rep to follow naming conventions
include/fmt/chrono.h
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| void write_floating_seconds(memory_buffer& buf, Duration duration, | ||
| int precision) { |
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Similarly, let's merge the two write_floating_seconds overloads.
include/fmt/chrono.h
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| bool is_floating_point = false; | ||
| bool has_precision = false; |
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We only need one flag for the condition has_precision && !is_floating_point, something like has_precision_integral.
include/fmt/chrono.h
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| const auto fractional = | ||
| detail::abs(d) - std::chrono::duration_cast<std::chrono::seconds>(d); | ||
| const auto& subseconds = |
include/fmt/chrono.h
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| if (precision >= 0) { | ||
| write_fractional_seconds<char_type>( | ||
| out, std::chrono::duration<rep, Period>(val), precision); | ||
| } else { | ||
| write_fractional_seconds<char_type>( | ||
| out, std::chrono::duration<rep, Period>(val)); | ||
| } |
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Now that write_fractional_seconds overloads have been merged, the if statement is no longer needed. You can just call
write_fractional_seconds<char_type>(
out, std::chrono::duration<rep, Period>(val), precision);
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Thanks! |
Continuation of #3122
Add precision modifier for seconds in chrono format and test for it.
It's became important for custom datetime types that store date, time and subseconds. I want to use chrono format for those types, but I have no way to control subsecond precision.
Use case:
So precision can be applied not only for %Q spec, but for %S too.