Allows layers to be partially pulled and resumed

Adds a sort of contrived test for resumable pulls

client/client_test.go

@@ -117,6 +117,7 @@ func TestPush(t *testing.T) {
 			t.Fatal(err)
 		}
 
+		writer.SetSize(len(blob.contents))
 		writer.Write(blob.contents)
 		writer.Close()
 	}
@@ -235,3 +236,133 @@ func TestPull(t *testing.T) {
 		}
 	}
 }
+
+func TestPullResume(t *testing.T) {
+	name := "hello/world"
+	tag := "sometag"
+	testBlobs := []testBlob{
+		{
+			digest:   "12345",
+			contents: []byte("some contents"),
+		},
+		{
+			digest:   "98765",
+			contents: []byte("some other contents"),
+		},
+	}
+	layers := make([]registry.FSLayer, len(testBlobs))
+	history := make([]registry.ManifestHistory, len(testBlobs))
+
+	for i, layer := range testBlobs {
+		layers[i] = registry.FSLayer{BlobSum: layer.digest}
+		history[i] = registry.ManifestHistory{V1Compatibility: layer.digest.String()}
+	}
+
+	manifest := &registry.ImageManifest{
+		Name:          name,
+		Tag:           tag,
+		Architecture:  "x86",
+		FSLayers:      layers,
+		History:       history,
+		SchemaVersion: 1,
+	}
+	manifestBytes, err := json.Marshal(manifest)
+
+	layerRequestResponseMappings := make([]testutil.RequestResponseMapping, 2*len(testBlobs))
+	for i, blob := range testBlobs {
+		layerRequestResponseMappings[2*i] = testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "GET",
+				Route:  "/v2/" + name + "/blob/" + blob.digest.String(),
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusOK,
+				Body:       blob.contents[:len(blob.contents)/2],
+				Headers: http.Header(map[string][]string{
+					"Content-Length": {fmt.Sprint(len(blob.contents))},
+				}),
+			},
+		}
+		layerRequestResponseMappings[2*i+1] = testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "GET",
+				Route:  "/v2/" + name + "/blob/" + blob.digest.String(),
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusOK,
+				Body:       blob.contents[len(blob.contents)/2:],
+			},
+		}
+	}
+
+	for i := 0; i < 3; i++ {
+		layerRequestResponseMappings = append(layerRequestResponseMappings, testutil.RequestResponseMap{
+			testutil.RequestResponseMapping{
+				Request: testutil.Request{
+					Method: "GET",
+					Route:  "/v2/" + name + "/manifest/" + tag,
+				},
+				Response: testutil.Response{
+					StatusCode: http.StatusOK,
+					Body:       manifestBytes,
+				},
+			},
+		}...)
+	}
+
+	handler := testutil.NewHandler(layerRequestResponseMappings)
+	server := httptest.NewServer(handler)
+	client := New(server.URL)
+	objectStore := &memoryObjectStore{
+		mutex:           new(sync.Mutex),
+		manifestStorage: make(map[string]*registry.ImageManifest),
+		layerStorage:    make(map[digest.Digest]Layer),
+	}
+
+	for attempts := 0; attempts < 3; attempts++ {
+		err = Pull(client, objectStore, name, tag)
+		if err == nil {
+			break
+		}
+	}
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	m, err := objectStore.Manifest(name, tag)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mBytes, err := json.Marshal(m)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(mBytes) != string(manifestBytes) {
+		t.Fatal("Incorrect manifest")
+	}
+
+	for _, blob := range testBlobs {
+		l, err := objectStore.Layer(blob.digest)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		reader, err := l.Reader()
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer reader.Close()
+
+		layerBytes, err := ioutil.ReadAll(reader)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if string(layerBytes) != string(blob.contents) {
+			t.Fatal("Incorrect blob")
+		}
+	}
+}