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Merged
bmehta001 merged 3 commits into from
Aug 5, 2026
Merged

Preserve sub-millisecond event timestamp precision #1516

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f9d020b
Preserve sub-millisecond event timestamp precision
bmehta001 Aug 3, 2026
babeb98
Cache precise Windows clock lookup
bmehta001 Aug 3, 2026
fa38087
Merge branch 'main' into bhamehta/fix-event-timestamp-precision
bmehta001 Aug 4, 2026
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28 changes: 23 additions & 5 deletions lib/pal/PAL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -430,7 +430,26 @@ namespace PAL_NS_BEGIN {
{
#ifdef _WIN32
FILETIME tocks;
::GetSystemTimeAsFileTime(&tocks);
// Resolve the precise API dynamically so the SDK retains its Windows 7
// runtime compatibility and falls back when the API is unavailable.
using GetSystemTimePreciseAsFileTimeProc = VOID (WINAPI*)(LPFILETIME);
static const GetSystemTimePreciseAsFileTimeProc getSystemTimePreciseAsFileTime =
[]() -> GetSystemTimePreciseAsFileTimeProc
{
HMODULE kernel32 = ::GetModuleHandleW(L"kernel32.dll");
return kernel32
? reinterpret_cast<GetSystemTimePreciseAsFileTimeProc>(
::GetProcAddress(kernel32, "GetSystemTimePreciseAsFileTime"))
: nullptr;
}();
if (getSystemTimePreciseAsFileTime)
{
getSystemTimePreciseAsFileTime(&tocks);
}
else
{
::GetSystemTimeAsFileTime(&tocks);
}
ULONGLONG ticks = (ULONGLONG(tocks.dwHighDateTime) << 32) | tocks.dwLowDateTime;
// number of days from beginning to 1601 multiplied by ticks per day
return ticks + 0x701ce1722770000ULL;
Expand All @@ -440,10 +459,9 @@ namespace PAL_NS_BEGIN {
// This UTC epoch contract has been signed in blood since C++20
std::chrono::time_point<std::chrono::system_clock> now = std::chrono::system_clock::now();
auto duration = now.time_since_epoch();
auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(duration).count();
uint64_t ticks = millis;
ticks *= 10000; // convert millis to ticks (1 tick = 100ns)
ticks += 0x89F7FF5F7B58000ULL; // UTC time 0 in .NET ticks
auto nanos = std::chrono::duration_cast<std::chrono::nanoseconds>(duration).count();
int64_t ticks = nanos / 100; // convert nanoseconds to .NET ticks (1 tick = 100ns)
ticks += static_cast<int64_t>(0x89F7FF5F7B58000ULL); // UTC time 0 in .NET ticks
return ticks;
#endif
}
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16 changes: 16 additions & 0 deletions tests/unittests/PalTests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -122,6 +122,22 @@ TEST_F(PalTests, SystemTime)
EXPECT_THAT(t1, Lt(t0 + 1000));
}

#if !defined(_WIN32) && !defined(_WIN64)
TEST_F(PalTests, SystemTimeInTicksPreservesSubMillisecondPrecision)
{
constexpr int64_t TicksPerMillisecond = 10000;
bool observedSubMillisecondTick = false;

for (int i = 0; i < 1000 && !observedSubMillisecondTick; ++i)
{
observedSubMillisecondTick =
PAL::getUtcSystemTimeinTicks() % TicksPerMillisecond != 0;
}

EXPECT_TRUE(observedSubMillisecondTick);
}
#endif

TEST_F(PalTests, FormatUtcTimestampMsAsISO8601)
{
EXPECT_THAT(PAL::formatUtcTimestampMsAsISO8601(0ll), Eq("1970-01-01T00:00:00.000Z"));
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