Implement gateway support Google Cloud Storage

vendor/cloud.google.com/go/storage/doc.go

@@ -0,0 +1,161 @@
+// 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 storage provides an easy way to work with Google Cloud Storage.
+Google Cloud Storage stores data in named objects, which are grouped into buckets.
+
+More information about Google Cloud Storage is available at
+https://cloud.google.com/storage/docs.
+
+All of the methods of this package use exponential backoff to retry calls
+that fail with certain errors, as described in
+https://cloud.google.com/storage/docs/exponential-backoff.
+
+Note: This package is in beta.  Some backwards-incompatible changes may occur.
+
+
+Creating a Client
+
+To start working with this package, create a client:
+
+    ctx := context.Background()
+    client, err := storage.NewClient(ctx)
+    if err != nil {
+        // TODO: Handle error.
+    }
+
+Buckets
+
+A Google Cloud Storage bucket is a collection of objects. To work with a
+bucket, make a bucket handle:
+
+    bkt := client.Bucket(bucketName)
+
+A handle is a reference to a bucket. You can have a handle even if the
+bucket doesn't exist yet. To create a bucket in Google Cloud Storage,
+call Create on the handle:
+
+    if err := bkt.Create(ctx, projectID, nil); err != nil {
+        // TODO: Handle error.
+    }
+
+Note that although buckets are associated with projects, bucket names are
+global across all projects.
+
+Each bucket has associated metadata, represented in this package by
+BucketAttrs. The third argument to BucketHandle.Create allows you to set
+the intial BucketAttrs of a bucket. To retrieve a bucket's attributes, use
+Attrs:
+
+    attrs, err := bkt.Attrs(ctx)
+    if err != nil {
+        // TODO: Handle error.
+    }
+    fmt.Printf("bucket %s, created at %s, is located in %s with storage class %s\n",
+        attrs.Name, attrs.Created, attrs.Location, attrs.StorageClass)
+
+Objects
+
+An object holds arbitrary data as a sequence of bytes, like a file. You
+refer to objects using a handle, just as with buckets. You can use the
+standard Go io.Reader and io.Writer interfaces to read and write
+object data:
+
+    obj := bkt.Object("data")
+    // Write something to obj.
+    // w implements io.Writer.
+    w := obj.NewWriter(ctx)
+    // Write some text to obj. This will overwrite whatever is there.
+    if _, err := fmt.Fprintf(w, "This object contains text.\n"); err != nil {
+        // TODO: Handle error.
+    }
+    // Close, just like writing a file.
+    if err := w.Close(); err != nil {
+        // TODO: Handle error.
+    }
+
+    // Read it back.
+    r, err := obj.NewReader(ctx)
+    if err != nil {
+        // TODO: Handle error.
+    }
+    defer r.Close()
+    if _, err := io.Copy(os.Stdout, r); err != nil {
+        // TODO: Handle error.
+    }
+    // Prints "This object contains text."
+
+Objects also have attributes, which you can fetch with Attrs:
+
+    objAttrs, err := obj.Attrs(ctx)
+    if err != nil {
+        // TODO: Handle error.
+    }
+    fmt.Printf("object %s has size %d and can be read using %s\n",
+        objAttrs.Name, objAttrs.Size, objAttrs.MediaLink)
+
+ACLs
+
+Both objects and buckets have ACLs (Access Control Lists). An ACL is a list of
+ACLRules, each of which specifies the role of a user, group or project. ACLs
+are suitable for fine-grained control, but you may prefer using IAM to control
+access at the project level (see
+https://cloud.google.com/storage/docs/access-control/iam).
+
+To list the ACLs of a bucket or object, obtain an ACLHandle and call its List method:
+
+    acls, err := obj.ACL().List(ctx)
+    if err != nil {
+        // TODO: Handle error.
+    }
+    for _, rule := range acls {
+        fmt.Printf("%s has role %s\n", rule.Entity, rule.Role)
+    }
+
+You can also set and delete ACLs.
+
+Conditions
+
+Every object has a generation and a metageneration. The generation changes
+whenever the content changes, and the metageneration changes whenever the
+metadata changes. Conditions let you check these values before an operation;
+the operation only executes if the conditions match. You can use conditions to
+prevent race conditions in read-modify-write operations.
+
+For example, say you've read an object's metadata into objAttrs. Now
+you want to write to that object, but only if its contents haven't changed
+since you read it. Here is how to express that:
+
+    w = obj.If(storage.Conditions{GenerationMatch: objAttrs.Generation}).NewWriter(ctx)
+    // Proceed with writing as above.
+
+Signed URLs
+
+You can obtain a URL that lets anyone read or write an object for a limited time.
+You don't need to create a client to do this. See the documentation of
+SignedURL for details.
+
+    url, err := storage.SignedURL(bucketName, "shared-object", opts)
+    if err != nil {
+        // TODO: Handle error.
+    }
+    fmt.Println(url)
+
+Authentication
+
+See examples of authorization and authentication at
+https://godoc.org/cloud.google.com/go#pkg-examples.
+*/
+package storage // import "cloud.google.com/go/storage"