diff options
Diffstat (limited to 'AK/Time.h')
| -rw-r--r-- | AK/Time.h | 45 |
1 files changed, 40 insertions, 5 deletions
@@ -26,6 +26,7 @@ #pragma once +#include <AK/Assertions.h> #include <AK/Platform.h> #include <AK/Types.h> @@ -100,18 +101,51 @@ public: return *this; } +private: + // This must be part of the header in order to make the various 'from_*' functions constexpr. + // However, sane_mod can only deal with a limited range of values for 'denominator', so this can't be made public. + ALWAYS_INLINE static constexpr i64 sane_mod(i64& numerator, i64 denominator) + { + VERIFY(2 <= denominator && denominator <= 1'000'000'000); + // '%' in C/C++ does not work in the obvious way: + // For example, -9 % 7 is -2, not +5. + // However, we want a representation like "(-2)*7 + (+5)". + i64 dividend = numerator / denominator; + numerator %= denominator; + if (numerator < 0) { + // Does not overflow: different signs. + numerator += denominator; + // Does not underflow: denominator >= 2. + dividend -= 1; + } + return dividend; + } + ALWAYS_INLINE static constexpr i32 sane_mod(i32& numerator, i32 denominator) + { + i64 numerator_64 = numerator; + i64 dividend = sane_mod(numerator_64, denominator); + // Does not underflow: numerator can only become smaller. + numerator = numerator_64; + // Does not overflow: Will be smaller than original value of 'numerator'. + return dividend; + } + +public: constexpr static Time from_seconds(i64 seconds) { return Time(seconds, 0); } constexpr static Time from_nanoseconds(i64 nanoseconds) { - return Time(nanoseconds / 1'000'000'000, nanoseconds % 1'000'000'000); + i64 seconds = sane_mod(nanoseconds, 1'000'000'000); + return Time(seconds, nanoseconds); } constexpr static Time from_microseconds(i64 microseconds) { - return Time(microseconds / 1'000'000, (microseconds % 1'000'000) * 1'000); + i64 seconds = sane_mod(microseconds, 1'000'000); + return Time(seconds, microseconds * 1'000); } constexpr static Time from_milliseconds(i64 milliseconds) { - return Time(milliseconds / 1'000, (milliseconds % 1'000) * 1'000'000); + i64 seconds = sane_mod(milliseconds, 1'000); + return Time(seconds, milliseconds * 1'000'000); } static Time from_timespec(const struct timespec&); static Time from_timeval(const struct timeval&); @@ -119,16 +153,17 @@ public: static Time zero() { return Time(0, 0); }; static Time max() { return Time(0x7fff'ffff'ffff'ffffLL, 999'999'999); }; - // Truncates "2.8 seconds" to 2 seconds. - // Truncates "-2.8 seconds" to -2 seconds. + // Truncates towards zero (2.8s to 2s, -2.8s to -2s). i64 to_truncated_seconds() const; i64 to_truncated_milliseconds() const; i64 to_truncated_microseconds() const; + // Rounds away from zero (2.3s to 3s, -2.3s to -3s). i64 to_seconds() const; i64 to_milliseconds() const; i64 to_microseconds() const; i64 to_nanoseconds() const; timespec to_timespec() const; + // Rounds towards -inf (it was the easiest to implement). timeval to_timeval() const; bool is_zero() const { return !m_seconds && !m_nanoseconds; } |