Initial commit

vendor/github.com/hyperhq/hypercli/distribution/metadata/metadata.go

@@ -0,0 +1,77 @@
+package metadata
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+// Store implements a K/V store for mapping distribution-related IDs
+// to on-disk layer IDs and image IDs. The namespace identifies the type of
+// mapping (i.e. "v1ids" or "artifacts"). MetadataStore is goroutine-safe.
+type Store interface {
+	// Get retrieves data by namespace and key.
+	Get(namespace string, key string) ([]byte, error)
+	// Set writes data indexed by namespace and key.
+	Set(namespace, key string, value []byte) error
+	// Delete removes data indexed by namespace and key.
+	Delete(namespace, key string) error
+}
+
+// FSMetadataStore uses the filesystem to associate metadata with layer and
+// image IDs.
+type FSMetadataStore struct {
+	sync.RWMutex
+	basePath string
+}
+
+// NewFSMetadataStore creates a new filesystem-based metadata store.
+func NewFSMetadataStore(basePath string) (*FSMetadataStore, error) {
+	if err := os.MkdirAll(basePath, 0700); err != nil {
+		return nil, err
+	}
+	return &FSMetadataStore{
+		basePath: basePath,
+	}, nil
+}
+
+func (store *FSMetadataStore) path(namespace, key string) string {
+	return filepath.Join(store.basePath, namespace, key)
+}
+
+// Get retrieves data by namespace and key. The data is read from a file named
+// after the key, stored in the namespace's directory.
+func (store *FSMetadataStore) Get(namespace string, key string) ([]byte, error) {
+	store.RLock()
+	defer store.RUnlock()
+
+	return ioutil.ReadFile(store.path(namespace, key))
+}
+
+// Set writes data indexed by namespace and key. The data is written to a file
+// named after the key, stored in the namespace's directory.
+func (store *FSMetadataStore) Set(namespace, key string, value []byte) error {
+	store.Lock()
+	defer store.Unlock()
+
+	path := store.path(namespace, key)
+	tempFilePath := path + ".tmp"
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+		return err
+	}
+	if err := ioutil.WriteFile(tempFilePath, value, 0644); err != nil {
+		return err
+	}
+	return os.Rename(tempFilePath, path)
+}
+
+// Delete removes data indexed by namespace and key. The data file named after
+// the key, stored in the namespace's directory is deleted.
+func (store *FSMetadataStore) Delete(namespace, key string) error {
+	store.Lock()
+	defer store.Unlock()
+
+	path := store.path(namespace, key)
+	return os.Remove(path)
+}