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AK: Implement now_time_from_clock for Windows

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Monotonic uses QueryPerformanceCounter, while realtime uses
GetSystemTimeAsFileTime. These should approximate clock_gettime
fairly accurately. The QPC implementation only grabs microseconds,
but if we have actual use cases for nanos, we can bump that up.

Co-authored-by: Andrew Kaster <akaster@serenityos.org>
This commit is contained in:
Cameron Youell 2023-08-30 16:57:14 +10:00 committed by Andrew Kaster
parent e7c209820d
commit e1710939ce
Notes: github-actions[bot] 2024-10-16 18:16:37 +00:00 
Author: https://github.com/stasoid
Commit: https://github.com/LadybirdBrowser/ladybird/commit/e1710939ce7
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1806
Reviewed-by: https://github.com/ADKaster ✅
2 changed files with 61 additions and 2 deletions
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57
AK/Time.cpp
View file

@ -6,8 +6,13 @@
#include <AK/Checked.h>
#include <AK/Time.h>
#include <sys/time.h>
#include <time.h>
#if defined(AK_OS_WINDOWS)
# include <profileapi.h>
#else
# include <sys/time.h>
#endif
namespace AK {
@ -201,12 +206,62 @@ Duration Duration::from_half_sanitized(i64 seconds, i32 extra_seconds, u32 nanos
}
namespace {
#if defined(AK_OS_WINDOWS)
# define CLOCK_REALTIME 0
# define CLOCK_MONOTONIC 1
// Ref https://stackoverflow.com/a/51974214
Duration now_time_from_filetime()
{
FILETIME ft {};
GetSystemTimeAsFileTime(&ft);
// Units: 1 LSB == 100 ns
ULARGE_INTEGER hundreds_of_nanos {
.LowPart = ft.dwLowDateTime,
.HighPart = ft.dwHighDateTime
};
constexpr u64 num_hundred_nanos_per_sec = 1000ULL * 1000ULL * 10ULL;
constexpr u64 seconds_from_jan_1601_to_jan_1970 = 11644473600ULL;
// To convert to Unix Epoch, subtract the number of hundred nanosecond intervals from Jan 1, 1601 to Jan 1, 1970.
hundreds_of_nanos.QuadPart -= (seconds_from_jan_1601_to_jan_1970 * num_hundred_nanos_per_sec);
return Duration::from_nanoseconds(hundreds_of_nanos.QuadPart * 100);
}
Duration now_time_from_query_performance_counter()
{
static LARGE_INTEGER ticks_per_second;
// FIXME: Limit to microseconds for now, but could probably use nanos?
static float ticks_per_microsecond;
if (ticks_per_second.QuadPart == 0) {
QueryPerformanceFrequency(&ticks_per_second);
VERIFY(ticks_per_second.QuadPart != 0);
ticks_per_microsecond = static_cast<float>(ticks_per_second.QuadPart) / 1'000'000.0F;
}
LARGE_INTEGER now_time {};
QueryPerformanceCounter(&now_time);
return Duration::from_microseconds(static_cast<i64>(now_time.QuadPart / ticks_per_microsecond));
}
Duration now_time_from_clock(int clock_id)
{
if (clock_id == CLOCK_REALTIME)
return now_time_from_filetime();
return now_time_from_query_performance_counter();
}
#else
static Duration now_time_from_clock(clockid_t clock_id)
{
timespec now_spec {};
::clock_gettime(clock_id, &now_spec);
return Duration::from_timespec(now_spec);
}
#endif
}
MonotonicTime MonotonicTime::now()

4
AK/Time.h
View file

@ -12,7 +12,11 @@
#include <AK/Checked.h>
#include <AK/Platform.h>
#include <AK/Types.h>
#if defined(AK_OS_WINDOWS)
# include <winsock2.h>
#else
# include <sys/time.h>
#endif
#include <time.h>
namespace AK {