| ... | ... | @@ -2956,7 +2956,22 @@ fn nowWindows(userdata: ?*anyopaque, clock: Io.Clock) Io.Clock.Error!Io.Timestam |
| 2956 | 2956 | }, |
| 2957 | 2957 | .awake, .boot => { |
| 2958 | 2958 | // QPC on windows doesn't fail on >= XP/2000 and includes time suspended. |
| 2959 | | return .{ .nanoseconds = windows.QueryPerformanceCounter() }; |
| 2959 | const qpc = windows.QueryPerformanceCounter(); |
| 2960 | // We don't need to cache QPF as it's internally just a memory read to KUSER_SHARED_DATA |
| 2961 | // (a read-only page of info updated and mapped by the kernel to all processes): |
| 2962 | // https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/ns-ntddk-kuser_shared_data |
| 2963 | // https://www.geoffchappell.com/studies/windows/km/ntoskrnl/inc/api/ntexapi_x/kuser_shared_data/index.htm |
| 2964 | const qpf = windows.QueryPerformanceFrequency(); |
| 2965 | |
| 2966 | // 10Mhz (1 qpc tick every 100ns) is a common enough QPF value that we can optimize on it. |
| 2967 | // https://github.com/microsoft/STL/blob/785143a0c73f030238ef618890fd4d6ae2b3a3a0/stl/inc/chrono#L694-L701 |
| 2968 | const common_qpf = 10_000_000; |
| 2969 | if (qpf == common_qpf) return .{ .nanoseconds = qpc * (std.time.ns_per_s / common_qpf) }; |
| 2970 | |
| 2971 | // Convert to ns using fixed point. |
| 2972 | const scale = @as(u64, std.time.ns_per_s << 32) / @as(u32, @intCast(qpf)); |
| 2973 | const result = (@as(u96, qpc) * scale) >> 32; |
| 2974 | return .{ .nanoseconds = @intCast(result) }; |
| 2960 | 2975 | }, |
| 2961 | 2976 | .cpu_process, |
| 2962 | 2977 | .cpu_thread, |
Zihad <zihadmahiuddin@gmail.com> 2025-11-23 16:15:20+06:00
Andrew Kelley <andrew@ziglang.org> 2025-11-25 03:46:24-08:00
lib