Add new metadata store.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/store/image/image.go

@@ -0,0 +1,120 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+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
+
+    http://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 image
+
+import (
+	"sync"
+
+	imagespec "github.com/opencontainers/image-spec/specs-go/v1"
+
+	"github.com/kubernetes-incubator/cri-containerd/pkg/store"
+)
+
+// Image contains all resources associated with the image. All fields
+// MUST not be mutated directly after created.
+type Image struct {
+	// Id of the image. Normally the digest of image config.
+	ID string
+	// Other names by which this image is known.
+	RepoTags []string
+	// Digests by which this image is known.
+	RepoDigests []string
+	// ChainID is the chainID of the image.
+	ChainID string
+	// Size is the compressed size of the image.
+	Size int64
+	// Config is the oci image config of the image.
+	Config *imagespec.ImageConfig
+	// TODO(random-liu): Add containerd image client.
+}
+
+// Store stores all images.
+type Store struct {
+	lock   sync.RWMutex
+	images map[string]Image
+	// TODO(random-liu): Add trunc index.
+}
+
+// LoadStore loads images from runtime.
+// TODO(random-liu): Implement LoadStore.
+func LoadStore() *Store { return nil }
+
+// NewStore creates an image store.
+func NewStore() *Store {
+	return &Store{images: make(map[string]Image)}
+}
+
+// Add an image into the store.
+func (s *Store) Add(img Image) {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+	i, ok := s.images[img.ID]
+	if !ok {
+		// If the image doesn't exist, add it.
+		s.images[img.ID] = img
+		return
+	}
+	// Or else, merge the repo tags/digests.
+	i.RepoTags = mergeStringSlices(i.RepoTags, img.RepoTags)
+	i.RepoDigests = mergeStringSlices(i.RepoDigests, img.RepoDigests)
+	s.images[img.ID] = i
+}
+
+// Get returns the image with specified id. Returns store.ErrNotExist if the
+// image doesn't exist.
+func (s *Store) Get(id string) (Image, error) {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+	if i, ok := s.images[id]; ok {
+		return i, nil
+	}
+	return Image{}, store.ErrNotExist
+}
+
+// List lists all images.
+func (s *Store) List() []Image {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+	var images []Image
+	for _, sb := range s.images {
+		images = append(images, sb)
+	}
+	return images
+}
+
+// Delete deletes the image with specified id.
+func (s *Store) Delete(id string) {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+	delete(s.images, id)
+}
+
+// mergeStringSlices merges 2 string slices into one and remove duplicated elements.
+func mergeStringSlices(a []string, b []string) []string {
+	set := map[string]struct{}{}
+	for _, s := range a {
+		set[s] = struct{}{}
+	}
+	for _, s := range b {
+		set[s] = struct{}{}
+	}
+	var ss []string
+	for s := range set {
+		ss = append(ss, s)
+	}
+	return ss
+}