Metadata and writing the object are now both committed together.

pkg/donutbox/donutbox.go

@@ -14,13 +14,58 @@ type DonutBox interface {
 	SetBucketMetadata(bucket string, metadata map[string]string) error
 
 	// object operations
-	GetObjectWriter(bucket, object string, column, blockSize uint) *io.PipeWriter
-	GetObjectReader(bucket, object string, column int) (io.Reader, error)
-	SetObjectMetadata(bucket, object string, metadata map[string]string) error
-	GetObjectMetadata(bucket, object string) (map[string]string, error)
+	GetObjectWriter(bucket, object string, column, blockSize uint) (*NewObject, error)
+	GetObjectReader(bucket, object string, column uint) (io.Reader, error)
+	GetObjectMetadata(bucket, object string, column uint) (map[string]string, error)
 }
 
 // Result is a result for async tasks
 type Result struct {
 	Err error
 }
+
+// CreateNewObject creates a new object wrapping a writer. Clients are not expected to use this directly. This is exposed for storage drivers.
+func CreateNewObject(writer *io.PipeWriter) *NewObject {
+	return &NewObject{writer: writer}
+}
+
+// NewObject wraps a writer and allows setting metadata. On a successful close, the object is committed by the backend.
+type NewObject struct {
+	metadata map[string]string
+	writer   *io.PipeWriter
+}
+
+// Write data
+func (newObject *NewObject) Write(data []byte) (int, error) {
+	return newObject.writer.Write(data)
+}
+
+// SetMetadata sets metadata for an object
+func (newObject *NewObject) SetMetadata(metadata map[string]string) {
+	newMetadata := make(map[string]string)
+	for k, v := range metadata {
+		newMetadata[k] = v
+	}
+	newObject.metadata = newMetadata
+}
+
+// Close and commit the object
+func (newObject *NewObject) Close() error {
+	return newObject.writer.Close()
+}
+
+// CloseWithError closes the object with an error, causing the backend to abandon the object
+func (newObject *NewObject) CloseWithError(err error) error {
+	return newObject.writer.CloseWithError(err)
+}
+
+// GetMetadata returns a copy of the metadata set metadata
+func (newObject *NewObject) GetMetadata() map[string]string {
+	newMetadata := make(map[string]string)
+	if newMetadata != nil {
+		for k, v := range newObject.metadata {
+			newMetadata[k] = v
+		}
+	}
+	return newMetadata
+}