mirror of
https://github.com/dutchcoders/transfer.sh.git
synced 2024-11-24 05:00:18 +01:00
176 lines
6 KiB
Go
176 lines
6 KiB
Go
// Copyright 2016 Google LLC
|
|
//
|
|
// 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.
|
|
|
|
See https://godoc.org/cloud.google.com/go for authentication, timeouts,
|
|
connection pooling and similar aspects of this package.
|
|
|
|
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. Retrying continues
|
|
indefinitely unless the controlling context is canceled or the client is closed. See
|
|
context.WithTimeout and context.WithCancel.
|
|
|
|
|
|
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.
|
|
}
|
|
|
|
The client will use your default application credentials.
|
|
|
|
If you only wish to access public data, you can create
|
|
an unauthenticated client with
|
|
|
|
client, err := storage.NewClient(ctx, option.WithoutAuthentication())
|
|
|
|
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 initial 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, but unlike buckets
|
|
you don't explicitly create an object. Instead, the first time you write
|
|
to an object it will be created. 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 either create the object or overwrite whatever is there already.
|
|
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)
|
|
|
|
Errors
|
|
|
|
Errors returned by this client are often of the type [`googleapi.Error`](https://godoc.org/google.golang.org/api/googleapi#Error).
|
|
These errors can be introspected for more information by type asserting to the richer `googleapi.Error` type. For example:
|
|
|
|
if e, ok := err.(*googleapi.Error); ok {
|
|
if e.Code == 409 { ... }
|
|
}
|
|
*/
|
|
package storage // import "cloud.google.com/go/storage"
|