feat(tools/nixery): Absorb Nixery into depot r/3978

This absorbs a josh-filtered Nix subtree into depot, at
//tools/nixery.

This subtree was created through `josh-filter ':prefix=tools/nixery'`,
which allows a filter on tools/nixery to yield the same commit hashes
as the original Nixery repository (allowing for history continuity).

Change-Id: Icc1a99bf1248226b91f437b0a90361d36fb0d327

1 files changed, 51 insertions, 0 deletions

diff --git a/tools/nixery/storage/storage.go b/tools/nixery/storage/storage.go
new file mode 100644
index 000000000000..fd496f440ae3
--- /dev/null
+++ b/tools/nixery/storage/storage.go
@@ -0,0 +1,51 @@
+// 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(ctx context.Context, path, contentType string, f 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
+}