std.time: more precise nanoTimestamp in windows

ziglang · Feb 12, 2025 · 63c6208 · 63c6208
1 parent 58f9288
commit 63c6208
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Showing 3 changed files with 3 additions and 7 deletions.
diff --git a/lib/std/os/windows/kernel32.zig b/lib/std/os/windows/kernel32.zig
@@ -656,9 +656,5 @@ 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 GetSystemTimePreciseAsFileTime(lpSystemTimeAsFileTime: *FILETIME) callconv(.winapi) void;
 pub extern "kernel32" fn GetSystemInfo(lpSystemInfo: *SYSTEM_INFO) callconv(.winapi) void;
diff --git a/lib/std/posix.zig b/lib/std/posix.zig
@@ -5710,7 +5710,7 @@ pub fn clock_gettime(clock_id: clockid_t) ClockGetTimeError!timespec {
     if (native_os == .windows) {
         if (clock_id == .REALTIME) {
             var ft: windows.FILETIME = undefined;
-            windows.kernel32.GetSystemTimeAsFileTime(&ft);
+            windows.kernel32.GetSystemTimePreciseAsFileTime(&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;

diff --git a/lib/std/time.zig b/lib/std/time.zig
@@ -51,7 +51,7 @@ pub fn nanoTimestamp() i128 {
             // which is 1601-01-01.
             const epoch_adj = epoch.windows * (ns_per_s / 100);
             var ft: windows.FILETIME = undefined;
-            windows.kernel32.GetSystemTimeAsFileTime(&ft);
+            windows.kernel32.GetSystemTimePreciseAsFileTime(&ft);
             const ft64 = (@as(u64, ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
             return @as(i128, @as(i64, @bitCast(ft64)) + epoch_adj) * 100;
         },