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std.time: more precise nanoTimestamp in windows #22871

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Feb 13, 2025
+7 −28
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std.time: more precise nanoTimestamp in windows #22871

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5 changes: 0 additions & 5 deletions lib/std/os/windows/kernel32.zig
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Expand Up @@ -656,9 +656,4 @@ pub extern "kernel32" fn SetLastError(

// Everything Else

// TODO:
// Wrapper around KUSER_SHARED_DATA.SystemTime.
// Much better to use NtQuerySystemTime or NtQuerySystemTimePrecise for guaranteed 0.1ns precision.
pub extern "kernel32" fn GetSystemTimeAsFileTime(lpSystemTimeAsFileTime: *FILETIME) callconv(.winapi) void;

pub extern "kernel32" fn GetSystemInfo(lpSystemInfo: *SYSTEM_INFO) callconv(.winapi) void;
1 change: 1 addition & 0 deletions lib/std/os/windows/ntdll.zig
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Expand Up @@ -92,6 +92,7 @@ pub extern "ntdll" fn RtlVirtualUnwind(
EstablisherFrame: *DWORD64,
ContextPointers: ?*KNONVOLATILE_CONTEXT_POINTERS,
) callconv(.winapi) *EXCEPTION_ROUTINE;
pub extern "ntdll" fn RtlGetSystemTimePrecise() callconv(.winapi) LARGE_INTEGER;
pub extern "ntdll" fn NtQueryInformationFile(
FileHandle: HANDLE,
IoStatusBlock: *IO_STATUS_BLOCK,
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22 changes: 4 additions & 18 deletions lib/std/posix.zig
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Expand Up @@ -5693,7 +5693,10 @@ pub const ClockGetTimeError = error{UnsupportedClock} || UnexpectedError;

pub fn clock_gettime(clock_id: clockid_t) ClockGetTimeError!timespec {
var tp: timespec = undefined;
if (native_os == .wasi and !builtin.link_libc) {

if (native_os == .windows) {
@compileError("Windows does not support POSIX; use Windows-specific API or cross-platform std.time API");
} else if (native_os == .wasi and !builtin.link_libc) {
var ts: timestamp_t = undefined;
switch (system.clock_time_get(clock_id, 1, &ts)) {
.SUCCESS => {
Expand All @@ -5707,23 +5710,6 @@ pub fn clock_gettime(clock_id: clockid_t) ClockGetTimeError!timespec {
}
return tp;
}
if (native_os == .windows) {
if (clock_id == .REALTIME) {
var ft: windows.FILETIME = undefined;
windows.kernel32.GetSystemTimeAsFileTime(&ft);
// FileTime has a granularity of 100 nanoseconds and uses the NTFS/Windows epoch.
const ft64 = (@as(u64, ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
const ft_per_s = std.time.ns_per_s / 100;
tp = .{
.sec = @as(i64, @intCast(ft64 / ft_per_s)) + std.time.epoch.windows,
.nsec = @as(c_long, @intCast(ft64 % ft_per_s)) * 100,
};
return tp;
} else {
// TODO POSIX implementation of CLOCK.MONOTONIC on Windows.
return error.UnsupportedClock;
}
}

switch (errno(system.clock_gettime(clock_id, &tp))) {
.SUCCESS => return tp,
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7 changes: 2 additions & 5 deletions lib/std/time.zig
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Expand Up @@ -47,13 +47,10 @@ pub fn microTimestamp() i64 {
pub fn nanoTimestamp() i128 {
switch (builtin.os.tag) {
.windows => {
// FileTime has a granularity of 100 nanoseconds and uses the NTFS/Windows epoch,
// RtlGetSystemTimePrecise() has a granularity of 100 nanoseconds and uses the NTFS/Windows epoch,
// which is 1601-01-01.
const epoch_adj = epoch.windows * (ns_per_s / 100);
var ft: windows.FILETIME = undefined;
windows.kernel32.GetSystemTimeAsFileTime(&ft);
const ft64 = (@as(u64, ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
return @as(i128, @as(i64, @bitCast(ft64)) + epoch_adj) * 100;
return @as(i128, windows.ntdll.RtlGetSystemTimePrecise() + epoch_adj) * 100;
},
.wasi => {
var ns: std.os.wasi.timestamp_t = undefined;
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