// Copyright 2019-2020 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
//
// https://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 implements an interface that can be implemented by
// storage backends, such as Google Cloud Storage or the local
// filesystem.
package storage
import (
"context"
"io"
"net/http"
)
type Persister = func(io.Writer) (string, int64, error)
type Backend interface {
// Name returns the name of the storage backend, for use in
// log messages and such.
Name() string
// Persist provides a user-supplied function with a writer
// that stores data in the storage backend.
//
// It needs to return the SHA256 hash of the data written as
// well as the total number of bytes, as those are required
// for the image manifest.
Persist(context.Context, string, Persister) (string, int64, error)
// Fetch retrieves data from the storage backend.
Fetch(ctx context.Context, path string) (io.ReadCloser, error)
// Move renames a path inside the storage backend. This is
// used for staging uploads while calculating their hashes.
Move(ctx context.Context, old, new string) error
// Serve provides a handler function to serve HTTP requests
// for objects in the storage backend.
Serve(digest string, r *http.Request, w http.ResponseWriter) error
}
