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package metadata // import "github.com/docker/docker/distribution/metadata"
import (
"os"
"path/filepath"
"sync"
"github.com/docker/docker/pkg/ioutils"
)
// 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, 0o700); 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 os.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)
if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
return err
}
return ioutils.AtomicWriteFile(path, value, 0o644)
}
// 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)
}
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