Move client package under registry package

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

docs/client/objectstore.go

@@ -0,0 +1,239 @@
+package client
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"sync"
+
+	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/manifest"
+)
+
+var (
+	// ErrLayerAlreadyExists is returned when attempting to create a layer with
+	// a tarsum that is already in use.
+	ErrLayerAlreadyExists = fmt.Errorf("Layer already exists")
+
+	// ErrLayerLocked is returned when attempting to write to a layer which is
+	// currently being written to.
+	ErrLayerLocked = fmt.Errorf("Layer locked")
+)
+
+// ObjectStore is an interface which is designed to approximate the docker
+// engine storage. This interface is subject to change to conform to the
+// future requirements of the engine.
+type ObjectStore interface {
+	// Manifest retrieves the image manifest stored at the given repository name
+	// and tag
+	Manifest(name, tag string) (*manifest.SignedManifest, error)
+
+	// WriteManifest stores an image manifest at the given repository name and
+	// tag
+	WriteManifest(name, tag string, manifest *manifest.SignedManifest) error
+
+	// Layer returns a handle to a layer for reading and writing
+	Layer(dgst digest.Digest) (Layer, error)
+}
+
+// Layer is a generic image layer interface.
+// A Layer may not be written to if it is already complete.
+type Layer interface {
+	// Reader returns a LayerReader or an error if the layer has not been
+	// written to or is currently being written to.
+	Reader() (LayerReader, error)
+
+	// Writer returns a LayerWriter or an error if the layer has been fully
+	// written to or is currently being written to.
+	Writer() (LayerWriter, error)
+
+	// Wait blocks until the Layer can be read from.
+	Wait() error
+}
+
+// LayerReader is a read-only handle to a Layer, which exposes the CurrentSize
+// and full Size in addition to implementing the io.ReadCloser interface.
+type LayerReader interface {
+	io.ReadCloser
+
+	// CurrentSize returns the number of bytes written to the underlying Layer
+	CurrentSize() int
+
+	// Size returns the full size of the underlying Layer
+	Size() int
+}
+
+// LayerWriter is a write-only handle to a Layer, which exposes the CurrentSize
+// and full Size in addition to implementing the io.WriteCloser interface.
+// SetSize must be called on this LayerWriter before it can be written to.
+type LayerWriter interface {
+	io.WriteCloser
+
+	// CurrentSize returns the number of bytes written to the underlying Layer
+	CurrentSize() int
+
+	// Size returns the full size of the underlying Layer
+	Size() int
+
+	// SetSize sets the full size of the underlying Layer.
+	// This must be called before any calls to Write
+	SetSize(int) error
+}
+
+// memoryObjectStore is an in-memory implementation of the ObjectStore interface
+type memoryObjectStore struct {
+	mutex           *sync.Mutex
+	manifestStorage map[string]*manifest.SignedManifest
+	layerStorage    map[digest.Digest]Layer
+}
+
+func (objStore *memoryObjectStore) Manifest(name, tag string) (*manifest.SignedManifest, error) {
+	objStore.mutex.Lock()
+	defer objStore.mutex.Unlock()
+
+	manifest, ok := objStore.manifestStorage[name+":"+tag]
+	if !ok {
+		return nil, fmt.Errorf("No manifest found with Name: %q, Tag: %q", name, tag)
+	}
+	return manifest, nil
+}
+
+func (objStore *memoryObjectStore) WriteManifest(name, tag string, manifest *manifest.SignedManifest) error {
+	objStore.mutex.Lock()
+	defer objStore.mutex.Unlock()
+
+	objStore.manifestStorage[name+":"+tag] = manifest
+	return nil
+}
+
+func (objStore *memoryObjectStore) Layer(dgst digest.Digest) (Layer, error) {
+	objStore.mutex.Lock()
+	defer objStore.mutex.Unlock()
+
+	layer, ok := objStore.layerStorage[dgst]
+	if !ok {
+		layer = &memoryLayer{cond: sync.NewCond(new(sync.Mutex))}
+		objStore.layerStorage[dgst] = layer
+	}
+
+	return layer, nil
+}
+
+type memoryLayer struct {
+	cond         *sync.Cond
+	contents     []byte
+	expectedSize int
+	writing      bool
+}
+
+func (ml *memoryLayer) Reader() (LayerReader, error) {
+	ml.cond.L.Lock()
+	defer ml.cond.L.Unlock()
+
+	if ml.contents == nil {
+		return nil, fmt.Errorf("Layer has not been written to yet")
+	}
+	if ml.writing {
+		return nil, ErrLayerLocked
+	}
+
+	return &memoryLayerReader{ml: ml, reader: bytes.NewReader(ml.contents)}, nil
+}
+
+func (ml *memoryLayer) Writer() (LayerWriter, error) {
+	ml.cond.L.Lock()
+	defer ml.cond.L.Unlock()
+
+	if ml.contents != nil {
+		if ml.writing {
+			return nil, ErrLayerLocked
+		}
+		if ml.expectedSize == len(ml.contents) {
+			return nil, ErrLayerAlreadyExists
+		}
+	} else {
+		ml.contents = make([]byte, 0)
+	}
+
+	ml.writing = true
+	return &memoryLayerWriter{ml: ml, buffer: bytes.NewBuffer(ml.contents)}, nil
+}
+
+func (ml *memoryLayer) Wait() error {
+	ml.cond.L.Lock()
+	defer ml.cond.L.Unlock()
+
+	if ml.contents == nil {
+		return fmt.Errorf("No writer to wait on")
+	}
+
+	for ml.writing {
+		ml.cond.Wait()
+	}
+
+	return nil
+}
+
+type memoryLayerReader struct {
+	ml     *memoryLayer
+	reader *bytes.Reader
+}
+
+func (mlr *memoryLayerReader) Read(p []byte) (int, error) {
+	return mlr.reader.Read(p)
+}
+
+func (mlr *memoryLayerReader) Close() error {
+	return nil
+}
+
+func (mlr *memoryLayerReader) CurrentSize() int {
+	return len(mlr.ml.contents)
+}
+
+func (mlr *memoryLayerReader) Size() int {
+	return mlr.ml.expectedSize
+}
+
+type memoryLayerWriter struct {
+	ml     *memoryLayer
+	buffer *bytes.Buffer
+}
+
+func (mlw *memoryLayerWriter) Write(p []byte) (int, error) {
+	if mlw.ml.expectedSize == 0 {
+		return 0, fmt.Errorf("Must set size before writing to layer")
+	}
+	wrote, err := mlw.buffer.Write(p)
+	mlw.ml.contents = mlw.buffer.Bytes()
+	return wrote, err
+}
+
+func (mlw *memoryLayerWriter) Close() error {
+	mlw.ml.cond.L.Lock()
+	defer mlw.ml.cond.L.Unlock()
+
+	return mlw.close()
+}
+
+func (mlw *memoryLayerWriter) close() error {
+	mlw.ml.writing = false
+	mlw.ml.cond.Broadcast()
+	return nil
+}
+
+func (mlw *memoryLayerWriter) CurrentSize() int {
+	return len(mlw.ml.contents)
+}
+
+func (mlw *memoryLayerWriter) Size() int {
+	return mlw.ml.expectedSize
+}
+
+func (mlw *memoryLayerWriter) SetSize(size int) error {
+	if !mlw.ml.writing {
+		return fmt.Errorf("Layer is closed for writing")
+	}
+	mlw.ml.expectedSize = size
+	return nil
+}