time: add methods to convert duration to microseconds and milliseconds

The return values are integers, as opposed to floats, since the fractionals can be derived from multiplying t.Seconds().

Fixes #28564

Change-Id: I3796227e1f64ead39ff0aacfbdce912d952f2994
GitHub-Last-Rev: b843ab740bf5a8216478322533521d6243fe1cb1
GitHub-Pull-Request: golang/go#30819
Reviewed-on: https://go-review.googlesource.com/c/go/+/167387
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/time/time.go

@@ -783,6 +783,12 @@ func fmtInt(buf []byte, v uint64) int {
 // Nanoseconds returns the duration as an integer nanosecond count.
 func (d Duration) Nanoseconds() int64 { return int64(d) }
 
+// Microseconds returns the duration as an integer microsecond count.
+func (d Duration) Microseconds() int64 { return int64(d) / 1e3 }
+
+// Milliseconds returns the duration as an integer millisecond count.
+func (d Duration) Milliseconds() int64 { return int64(d) / 1e6 }
+
 // These methods return float64 because the dominant
 // use case is for printing a floating point number like 1.5s, and
 // a truncation to integer would make them not useful in those cases.

src/time/time_test.go

@@ -1021,7 +1021,39 @@ var nsDurationTests = []struct {
 func TestDurationNanoseconds(t *testing.T) {
 	for _, tt := range nsDurationTests {
 		if got := tt.d.Nanoseconds(); got != tt.want {
-			t.Errorf("d.Nanoseconds() = %d; want: %d", got, tt.want)
+			t.Errorf("Duration(%s).Nanoseconds() = %d; want: %d", tt.d, got, tt.want)
+		}
+	}
+}
+
+var usDurationTests = []struct {
+	d    Duration
+	want int64
+}{
+	{Duration(-1000), -1},
+	{Duration(1000), 1},
+}
+
+func TestDurationMicroseconds(t *testing.T) {
+	for _, tt := range usDurationTests {
+		if got := tt.d.Microseconds(); got != tt.want {
+			t.Errorf("Duration(%s).Microseconds() = %d; want: %d", tt.d, got, tt.want)
+		}
+	}
+}
+
+var msDurationTests = []struct {
+	d    Duration
+	want int64
+}{
+	{Duration(-1000000), -1},
+	{Duration(1000000), 1},
+}
+
+func TestDurationMilliseconds(t *testing.T) {
+	for _, tt := range msDurationTests {
+		if got := tt.d.Milliseconds(); got != tt.want {
+			t.Errorf("Duration(%s).Milliseconds() = %d; want: %d", tt.d, got, tt.want)
 		}
 	}
 }
@@ -1036,7 +1068,7 @@ var secDurationTests = []struct {
 func TestDurationSeconds(t *testing.T) {
 	for _, tt := range secDurationTests {
 		if got := tt.d.Seconds(); got != tt.want {
-			t.Errorf("d.Seconds() = %g; want: %g", got, tt.want)
+			t.Errorf("Duration(%s).Seconds() = %g; want: %g", tt.d, got, tt.want)
 		}
 	}
 }
@@ -1055,7 +1087,7 @@ var minDurationTests = []struct {
 func TestDurationMinutes(t *testing.T) {
 	for _, tt := range minDurationTests {
 		if got := tt.d.Minutes(); got != tt.want {
-			t.Errorf("d.Minutes() = %g; want: %g", got, tt.want)
+			t.Errorf("Duration(%s).Minutes() = %g; want: %g", tt.d, got, tt.want)
 		}
 	}
 }
@@ -1074,7 +1106,7 @@ var hourDurationTests = []struct {
 func TestDurationHours(t *testing.T) {
 	for _, tt := range hourDurationTests {
 		if got := tt.d.Hours(); got != tt.want {
-			t.Errorf("d.Hours() = %g; want: %g", got, tt.want)
+			t.Errorf("Duration(%s).Hours() = %g; want: %g", tt.d, got, tt.want)
 		}
 	}
 }