1 files changed, 38 insertions, 0 deletions
diff --git a/src/testing/testing_windows.go b/src/testing/testing_windows.go
index fd48ae9579..ebe4e01d23 100644
--- a/src/testing/testing_windows.go
+++ b/src/testing/testing_windows.go
@@ -9,7 +9,9 @@ package testing
 import (
 	"errors"
 	"internal/syscall/windows"
+	"math/bits"
 	"syscall"
+	"time"
 )
 
 // isWindowsRetryable reports whether err is a Windows error code
@@ -30,3 +32,39 @@ func isWindowsRetryable(err error) bool {
 	}
 	return false
 }
+
+// highPrecisionTime represents a single point in time with query performance counter.
+// time.Time on Windows has low system granularity, which is not suitable for
+// measuring short time intervals.
+//
+// TODO: If Windows runtime implements high resolution timing then highPrecisionTime
+// can be removed.
+type highPrecisionTime struct {
+	now int64
+}
+
+// highPrecisionTimeNow returns high precision time for benchmarking.
+func highPrecisionTimeNow() highPrecisionTime {
+	var t highPrecisionTime
+	// This should always succeed for Windows XP and above.
+	t.now = windows.QueryPerformanceCounter()
+	return t
+}
+
+func (a highPrecisionTime) sub(b highPrecisionTime) time.Duration {
+	delta := a.now - b.now
+
+	if queryPerformanceFrequency == 0 {
+		queryPerformanceFrequency = windows.QueryPerformanceFrequency()
+	}
+	hi, lo := bits.Mul64(uint64(delta), uint64(time.Second)/uint64(time.Nanosecond))
+	quo, _ := bits.Div64(hi, lo, uint64(queryPerformanceFrequency))
+	return time.Duration(quo)
+}
+
+var queryPerformanceFrequency int64
+
+// highPrecisionTimeSince returns duration since a.
+func highPrecisionTimeSince(a highPrecisionTime) time.Duration {
+	return highPrecisionTimeNow().sub(a)
+}