Vendor dependencies for GCS

vendor/cloud.google.com/go/internal/retry.go

@@ -0,0 +1,56 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+	"fmt"
+	"time"
+
+	gax "github.com/googleapis/gax-go"
+
+	"golang.org/x/net/context"
+)
+
+// Retry calls the supplied function f repeatedly according to the provided
+// backoff parameters. It returns when one of the following occurs:
+// When f's first return value is true, Retry immediately returns with f's second
+// return value.
+// When the provided context is done, Retry returns with an error that
+// includes both ctx.Error() and the last error returned by f.
+func Retry(ctx context.Context, bo gax.Backoff, f func() (stop bool, err error)) error {
+	return retry(ctx, bo, f, gax.Sleep)
+}
+
+func retry(ctx context.Context, bo gax.Backoff, f func() (stop bool, err error),
+	sleep func(context.Context, time.Duration) error) error {
+	var lastErr error
+	for {
+		stop, err := f()
+		if stop {
+			return err
+		}
+		// Remember the last "real" error from f.
+		if err != nil && err != context.Canceled && err != context.DeadlineExceeded {
+			lastErr = err
+		}
+		p := bo.Pause()
+		if cerr := sleep(ctx, p); cerr != nil {
+			if lastErr != nil {
+				return fmt.Errorf("%v; last function err: %v", cerr, lastErr)
+			}
+			return cerr
+		}
+	}
+}