improve performance on copy

common/buf/copy_test.go

@@ -1,7 +1,8 @@
 package buf_test
 
 import (
-	"crypto/rand"
+	"io"
+	"math/rand"
 	"testing"
 
 	"github.com/golang/mock/gomock"
@@ -39,7 +40,7 @@ func TestWriteError(t *testing.T) {
 	mockWriter := mocks.NewWriter(mockCtl)
 	mockWriter.EXPECT().Write(gomock.Any()).Return(0, errors.New("error"))
 
-	err := buf.Copy(buf.NewReader(rand.Reader), buf.NewWriter(mockWriter))
+	err := buf.Copy(buf.NewReader(rand.New(rand.NewSource(0))), buf.NewWriter(mockWriter))
 	if err == nil {
 		t.Fatal("expected error, but nil")
 	}
@@ -52,3 +53,13 @@ func TestWriteError(t *testing.T) {
 		t.Fatal("unexpected error message: ", err.Error())
 	}
 }
+
+func BenchmarkCopy(b *testing.B) {
+	reader := buf.NewReader(io.LimitReader(rand.New(rand.NewSource(0)), 1024*10))
+	writer := buf.Discard
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = buf.Copy(reader, writer)
+	}
+}