Adding interfaces for donut driver

pkg/storage/donut/donut.go

@@ -0,0 +1,45 @@
+package donut
+
+import "io"
+
+// INTERFACES
+
+// Donut interface
+type Donut interface {
+	CreateBucket(bucket string) error
+	GetBuckets() ([]string, error)
+	GetObject(bucket, object string) (io.ReadCloser, error)
+	GetObjectMetadata(bucket, object string) (map[string]string, error)
+	GetObjectWriter(bucket, object string) (ObjectWriter, error)
+}
+
+// Bucket is an interface for managing buckets
+type Bucket interface {
+	GetObject(object string) (io.Reader, error)
+	GetObjectMetadata(object string) (map[string]string, error)
+	GetObjectWriter(object string) (ObjectWriter, error)
+	GetObjects() ([]string, error)
+}
+
+// Disk is an interface for managing disks
+type Disk interface {
+	GetBuckets(object string) ([]string, error)
+}
+
+// ObjectWriter is an interface for writing new objects
+type ObjectWriter interface {
+	Write([]byte) error
+	Close() error
+	CloseWithError(error) error
+
+	SetMetadata(map[string]string)
+	GetMetadata() map[string]string
+}
+
+// InternalObjectWriter is an interface for use internally to donut
+type InternalObjectWriter interface {
+	ObjectWriter
+
+	SetDonutMetadata(map[string]string)
+	GetDonutMetadata() map[string]string
+}