metadata: merge storage into package

The implementations for the storage of metadata have been merged into a
single metadata package where they can share storage primitives and
techniques. The is a requisite for the addition of namespaces, which
will require a coordinated layout for records to be organized by
namespace.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

metadata/buckets.go

@@ -0,0 +1,107 @@
+package metadata
+
+import (
+	"github.com/boltdb/bolt"
+	"github.com/containerd/containerd/log"
+)
+
+var (
+	bucketKeyStorageVersion = []byte("v1")
+	bucketKeyImages         = []byte("images")
+	bucketKeyContainers     = []byte("containers")
+
+	bucketKeyDigest    = []byte("digest")
+	bucketKeyMediaType = []byte("mediatype")
+	bucketKeySize      = []byte("size")
+	bucketKeyLabels    = []byte("labels")
+	bucketKeyImage     = []byte("image")
+	bucketKeyRuntime   = []byte("runtime")
+	bucketKeySpec      = []byte("spec")
+	bucketKeyRootFS    = []byte("rootfs")
+)
+
+// InitDB will initialize the database for use. The database must be opened for
+// write and the caller must not be holding an open transaction.
+func InitDB(db *bolt.DB) error {
+	log.L.Debug("init db")
+	return db.Update(func(tx *bolt.Tx) error {
+		if _, err := createBucketIfNotExists(tx, bucketKeyStorageVersion, bucketKeyImages); err != nil {
+			return err
+		}
+		if _, err := createBucketIfNotExists(tx, bucketKeyStorageVersion, bucketKeyContainers); err != nil {
+			return err
+		}
+		return nil
+	})
+}
+
+func getBucket(tx *bolt.Tx, keys ...[]byte) *bolt.Bucket {
+	bkt := tx.Bucket(keys[0])
+
+	for _, key := range keys[1:] {
+		if bkt == nil {
+			break
+		}
+		bkt = bkt.Bucket(key)
+	}
+
+	return bkt
+}
+
+func createBucketIfNotExists(tx *bolt.Tx, keys ...[]byte) (*bolt.Bucket, error) {
+	bkt, err := tx.CreateBucketIfNotExists(keys[0])
+	if err != nil {
+		return nil, err
+	}
+
+	for _, key := range keys[1:] {
+		bkt, err = bkt.CreateBucketIfNotExists(key)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return bkt, nil
+}
+
+func withImagesBucket(tx *bolt.Tx, fn func(bkt *bolt.Bucket) error) error {
+	bkt := getImagesBucket(tx)
+	if bkt == nil {
+		return ErrNotFound
+	}
+
+	return fn(bkt)
+}
+
+func withImageBucket(tx *bolt.Tx, name string, fn func(bkt *bolt.Bucket) error) error {
+	bkt := getImageBucket(tx, name)
+	if bkt == nil {
+		return ErrNotFound
+	}
+
+	return fn(bkt)
+}
+
+func getImagesBucket(tx *bolt.Tx) *bolt.Bucket {
+	return getBucket(tx, bucketKeyStorageVersion, bucketKeyImages)
+}
+
+func getImageBucket(tx *bolt.Tx, name string) *bolt.Bucket {
+	return getBucket(tx, bucketKeyStorageVersion, bucketKeyImages, []byte(name))
+}
+
+func createContainersBucket(tx *bolt.Tx) (*bolt.Bucket, error) {
+	bkt, err := tx.CreateBucketIfNotExists(bucketKeyStorageVersion)
+	if err != nil {
+		return nil, err
+	}
+	return bkt.CreateBucketIfNotExists(bucketKeyContainers)
+}
+
+func getContainersBucket(tx *bolt.Tx) *bolt.Bucket {
+	return getBucket(tx, bucketKeyStorageVersion, bucketKeyContainers)
+}
+
+func getContainerBucket(tx *bolt.Tx, id string) *bolt.Bucket {
+	return getBucket(tx, bucketKeyStorageVersion, bucketKeyContainers, []byte(id))
+}