syncs: add Semaphore

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2021-03-23 12:15:08 -07:00
parent 9643d8b34d
commit 77ec80538a
2 changed files with 72 additions and 2 deletions
@@ -4,7 +4,10 @@

 package syncs

-import "testing"
+import (
+	"context"
+	"testing"
+)

 func TestWaitGroupChan(t *testing.T) {
 	wg := NewWaitGroupChan()
@@ -48,3 +51,25 @@ func TestClosedChan(t *testing.T) {
 		}
 	}
 }
+
+func TestSemaphore(t *testing.T) {
+	s := NewSemaphore(2)
+	s.Acquire()
+	if !s.TryAcquire() {
+		t.Fatal("want true")
+	}
+	if s.TryAcquire() {
+		t.Fatal("want false")
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if s.AcquireContext(ctx) {
+		t.Fatal("want false")
+	}
+	s.Release()
+	if !s.AcquireContext(context.Background()) {
+		t.Fatal("want true")
+	}
+	s.Release()
+	s.Release()
+}