Code restructuring, assigning proper subsystems to each

- Drivers contain
    * donut/*
    * file/*
    * memory/*

 - Storage format contains
    * donut/*
      - GetObject() --> renamed to GetObjectReader()
      - Deleted stale objectwriter.go, renamed donutwriter.go to object_writer.go

Simplifying, and documenting codebase further

pkg/storage/donut/bucket.go

@@ -1,11 +1,12 @@
 package donut
 
-type bucketDriver struct {
+type donutBucket struct {
 	nodes   []string
 	objects map[string][]byte
 }
 
-func (b bucketDriver) GetNodes() ([]string, error) {
+// GetNodes - get list of associated nodes for a given bucket
+func (b donutBucket) GetNodes() ([]string, error) {
 	var nodes []string
 	for _, node := range b.nodes {
 		nodes = append(nodes, node)

pkg/storage/donut/donut.go

@@ -1,50 +1,160 @@
 package donut
 
 import (
+	"errors"
 	"io"
+	"sort"
+	"strconv"
+	"strings"
 )
 
-// INTERFACES
-
-// Donut interface
-type Donut interface {
-	CreateBucket(bucket string) error
-	GetObject(bucket, object string) (io.ReadCloser, error)
-	GetObjectMetadata(bucket, object string) (map[string]string, error)
-	GetObjectWriter(bucket, object string) (ObjectWriter, error)
-	ListBuckets() ([]string, error)
-	ListObjects(bucket string) ([]string, error)
+type donut struct {
+	buckets map[string]Bucket
+	nodes   map[string]Node
 }
 
-// Bucket interface
-type Bucket interface {
-	GetNodes() ([]string, error)
+// NewDonut - instantiate new donut
+func NewDonut(root string) Donut {
+	nodes := make(map[string]Node)
+	nodes["localhost"] = localDirectoryNode{root: root}
+	d := donut{
+		buckets: make(map[string]Bucket),
+		nodes:   nodes,
+	}
+	return d
 }
 
-// Node interface
-type Node interface {
-	CreateBucket(bucket string) error
-	GetBuckets() ([]string, error)
-	GetDonutMetadata(bucket, object string) (map[string]string, error)
-	GetMetadata(bucket, object string) (map[string]string, error)
-	GetReader(bucket, object string) (io.ReadCloser, error)
-	GetWriter(bucket, object string) (Writer, error)
-	ListObjects(bucket string) ([]string, error)
+// CreateBucket - create a new bucket
+func (d donut) CreateBucket(bucketName string) error {
+	if _, ok := d.buckets[bucketName]; ok == false {
+		bucketName = strings.TrimSpace(bucketName)
+		if bucketName == "" {
+			return errors.New("Cannot create bucket with no name")
+		}
+		// assign nodes
+		// TODO assign other nodes
+		nodes := make([]string, 16)
+		for i := 0; i < 16; i++ {
+			nodes[i] = "localhost"
+			if node, ok := d.nodes["localhost"]; ok {
+				node.CreateBucket(bucketName + ":0:" + strconv.Itoa(i))
+			}
+		}
+		bucket := donutBucket{
+			nodes: nodes,
+		}
+		d.buckets[bucketName] = bucket
+		return nil
+	}
+	return errors.New("Bucket exists")
 }
 
-// ObjectWriter interface
-type ObjectWriter interface {
-	Close() error
-	CloseWithError(error) error
-	GetMetadata() (map[string]string, error)
-	SetMetadata(map[string]string) error
-	Write([]byte) (int, error)
+// ListBuckets - list all buckets
+func (d donut) ListBuckets() ([]string, error) {
+	var buckets []string
+	for bucket := range d.buckets {
+		buckets = append(buckets, bucket)
+	}
+	sort.Strings(buckets)
+	return buckets, nil
 }
 
-// Writer interface
-type Writer interface {
-	ObjectWriter
-
-	GetDonutMetadata() (map[string]string, error)
-	SetDonutMetadata(map[string]string) error
+// GetObjectWriter - get a new writer interface for a new object
+func (d donut) GetObjectWriter(bucketName, objectName string) (ObjectWriter, error) {
+	if bucket, ok := d.buckets[bucketName]; ok == true {
+		writers := make([]Writer, 16)
+		nodes, err := bucket.GetNodes()
+		if err != nil {
+			return nil, err
+		}
+		for i, nodeID := range nodes {
+			if node, ok := d.nodes[nodeID]; ok == true {
+				writer, err := node.GetWriter(bucketName+":0:"+strconv.Itoa(i), objectName)
+				if err != nil {
+					for _, writerToClose := range writers {
+						if writerToClose != nil {
+							writerToClose.CloseWithError(err)
+						}
+					}
+					return nil, err
+				}
+				writers[i] = writer
+			}
+		}
+		return newErasureWriter(writers), nil
+	}
+	return nil, errors.New("Bucket not found")
+}
+
+// GetObjectReader - get a new reader interface for a new object
+func (d donut) GetObjectReader(bucketName, objectName string) (io.ReadCloser, error) {
+	r, w := io.Pipe()
+	if bucket, ok := d.buckets[bucketName]; ok == true {
+		readers := make([]io.ReadCloser, 16)
+		nodes, err := bucket.GetNodes()
+		if err != nil {
+			return nil, err
+		}
+		var metadata map[string]string
+		for i, nodeID := range nodes {
+			if node, ok := d.nodes[nodeID]; ok == true {
+				bucketID := bucketName + ":0:" + strconv.Itoa(i)
+				reader, err := node.GetReader(bucketID, objectName)
+				if err != nil {
+					return nil, err
+				}
+				readers[i] = reader
+				if metadata == nil {
+					metadata, err = node.GetDonutMetadata(bucketID, objectName)
+					if err != nil {
+						return nil, err
+					}
+				}
+			}
+		}
+		go erasureReader(readers, metadata, w)
+		return r, nil
+	}
+	return nil, errors.New("Bucket not found")
+}
+
+// GetObjectMetadata returns metadata for a given object in a bucket
+func (d donut) GetObjectMetadata(bucketName, object string) (map[string]string, error) {
+	if bucket, ok := d.buckets[bucketName]; ok {
+		nodes, err := bucket.GetNodes()
+		if err != nil {
+			return nil, err
+		}
+		if node, ok := d.nodes[nodes[0]]; ok {
+			bucketID := bucketName + ":0:0"
+			metadata, err := node.GetMetadata(bucketID, object)
+			if err != nil {
+				return nil, err
+			}
+			donutMetadata, err := node.GetDonutMetadata(bucketID, object)
+			if err != nil {
+				return nil, err
+			}
+			metadata["sys.created"] = donutMetadata["created"]
+			metadata["sys.md5"] = donutMetadata["md5"]
+			metadata["sys.size"] = donutMetadata["size"]
+			return metadata, nil
+		}
+		return nil, errors.New("Cannot connect to node: " + nodes[0])
+	}
+	return nil, errors.New("Bucket not found")
+}
+
+// ListObjects - list all the available objects in a bucket
+func (d donut) ListObjects(bucketName string) ([]string, error) {
+	if bucket, ok := d.buckets[bucketName]; ok {
+		nodes, err := bucket.GetNodes()
+		if err != nil {
+			return nil, err
+		}
+		if node, ok := d.nodes[nodes[0]]; ok {
+			return node.ListObjects(bucketName + ":0:0")
+		}
+	}
+	return nil, errors.New("Bucket not found")
 }

pkg/storage/donut/donut_test.go

@@ -1,14 +1,14 @@
 package donut
 
 import (
-	"testing"
-
 	"bytes"
-	. "gopkg.in/check.v1"
 	"io"
 	"io/ioutil"
 	"os"
+	"testing"
 	"time"
+
+	. "gopkg.in/check.v1"
 )
 
 func Test(t *testing.T) { TestingT(t) }
@@ -21,7 +21,7 @@ func (s *MySuite) TestEmptyBucket(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 
 	// check buckets are empty
 	buckets, err := donut.ListBuckets()
@@ -33,7 +33,7 @@ func (s *MySuite) TestBucketWithoutNameFails(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 	// fail to create new bucket without a name
 	err = donut.CreateBucket("")
 	c.Assert(err, Not(IsNil))
@@ -46,7 +46,7 @@ func (s *MySuite) TestCreateBucketAndList(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 	// create bucket
 	err = donut.CreateBucket("foo")
 	c.Assert(err, IsNil)
@@ -61,7 +61,7 @@ func (s *MySuite) TestCreateBucketWithSameNameFails(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 	err = donut.CreateBucket("foo")
 	c.Assert(err, IsNil)
 
@@ -73,7 +73,7 @@ func (s *MySuite) TestCreateMultipleBucketsAndList(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 	// add a second bucket
 	err = donut.CreateBucket("foo")
 	c.Assert(err, IsNil)
@@ -97,7 +97,7 @@ func (s *MySuite) TestNewObjectFailsWithoutBucket(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 
 	writer, err := donut.GetObjectWriter("foo", "obj")
 	c.Assert(err, Not(IsNil))
@@ -108,7 +108,7 @@ func (s *MySuite) TestNewObjectFailsWithEmptyName(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 
 	writer, err := donut.GetObjectWriter("foo", "")
 	c.Assert(err, Not(IsNil))
@@ -123,7 +123,7 @@ func (s *MySuite) TestNewObjectCanBeWritten(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 
 	err = donut.CreateBucket("foo")
 	c.Assert(err, IsNil)
@@ -153,7 +153,7 @@ func (s *MySuite) TestNewObjectCanBeWritten(c *C) {
 
 	c.Assert(err, IsNil)
 
-	reader, err := donut.GetObject("foo", "obj")
+	reader, err := donut.GetObjectReader("foo", "obj")
 	c.Assert(err, IsNil)
 
 	var actualData bytes.Buffer
@@ -175,7 +175,7 @@ func (s *MySuite) TestMultipleNewObjects(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 
 	c.Assert(donut.CreateBucket("foo"), IsNil)
 	writer, err := donut.GetObjectWriter("foo", "obj1")
@@ -190,7 +190,7 @@ func (s *MySuite) TestMultipleNewObjects(c *C) {
 
 	//	c.Skip("not complete")
 
-	reader, err := donut.GetObject("foo", "obj1")
+	reader, err := donut.GetObjectReader("foo", "obj1")
 	c.Assert(err, IsNil)
 	var readerBuffer1 bytes.Buffer
 	_, err = io.Copy(&readerBuffer1, reader)
@@ -198,7 +198,7 @@ func (s *MySuite) TestMultipleNewObjects(c *C) {
 	//	c.Skip("Not Implemented")
 	c.Assert(readerBuffer1.Bytes(), DeepEquals, []byte("one"))
 
-	reader, err = donut.GetObject("foo", "obj2")
+	reader, err = donut.GetObjectReader("foo", "obj2")
 	c.Assert(err, IsNil)
 	var readerBuffer2 bytes.Buffer
 	_, err = io.Copy(&readerBuffer2, reader)
@@ -215,7 +215,7 @@ func (s *MySuite) TestSysPrefixShouldFail(c *C) {
 	root, err := ioutil.TempDir(os.TempDir(), "donut-")
 	c.Assert(err, IsNil)
 	defer os.RemoveAll(root)
-	donut := NewDonutDriver(root)
+	donut := NewDonut(root)
 
 	c.Assert(donut.CreateBucket("foo"), IsNil)
 	writer, err := donut.GetObjectWriter("foo", "obj1")

pkg/storage/donut/donutdriver.go

@@ -1,155 +0,0 @@
-package donut
-
-import (
-	"errors"
-	"io"
-	"sort"
-	"strconv"
-	"strings"
-)
-
-type donutDriver struct {
-	buckets map[string]Bucket
-	nodes   map[string]Node
-}
-
-// NewDonutDriver - instantiate new donut driver
-func NewDonutDriver(root string) Donut {
-	nodes := make(map[string]Node)
-	nodes["localhost"] = localDirectoryNode{root: root}
-	driver := donutDriver{
-		buckets: make(map[string]Bucket),
-		nodes:   nodes,
-	}
-	return driver
-}
-
-func (driver donutDriver) CreateBucket(bucketName string) error {
-	if _, ok := driver.buckets[bucketName]; ok == false {
-		bucketName = strings.TrimSpace(bucketName)
-		if bucketName == "" {
-			return errors.New("Cannot create bucket with no name")
-		}
-		// assign nodes
-		// TODO assign other nodes
-		nodes := make([]string, 16)
-		for i := 0; i < 16; i++ {
-			nodes[i] = "localhost"
-			if node, ok := driver.nodes["localhost"]; ok {
-				node.CreateBucket(bucketName + ":0:" + strconv.Itoa(i))
-			}
-		}
-		bucket := bucketDriver{
-			nodes: nodes,
-		}
-		driver.buckets[bucketName] = bucket
-		return nil
-	}
-	return errors.New("Bucket exists")
-}
-
-func (driver donutDriver) ListBuckets() ([]string, error) {
-	var buckets []string
-	for bucket := range driver.buckets {
-		buckets = append(buckets, bucket)
-	}
-	sort.Strings(buckets)
-	return buckets, nil
-}
-
-func (driver donutDriver) GetObjectWriter(bucketName, objectName string) (ObjectWriter, error) {
-	if bucket, ok := driver.buckets[bucketName]; ok == true {
-		writers := make([]Writer, 16)
-		nodes, err := bucket.GetNodes()
-		if err != nil {
-			return nil, err
-		}
-		for i, nodeID := range nodes {
-			if node, ok := driver.nodes[nodeID]; ok == true {
-				writer, err := node.GetWriter(bucketName+":0:"+strconv.Itoa(i), objectName)
-				if err != nil {
-					for _, writerToClose := range writers {
-						if writerToClose != nil {
-							writerToClose.CloseWithError(err)
-						}
-					}
-					return nil, err
-				}
-				writers[i] = writer
-			}
-		}
-		return newErasureWriter(writers), nil
-	}
-	return nil, errors.New("Bucket not found")
-}
-
-func (driver donutDriver) GetObject(bucketName, objectName string) (io.ReadCloser, error) {
-	r, w := io.Pipe()
-	if bucket, ok := driver.buckets[bucketName]; ok == true {
-		readers := make([]io.ReadCloser, 16)
-		nodes, err := bucket.GetNodes()
-		if err != nil {
-			return nil, err
-		}
-		var metadata map[string]string
-		for i, nodeID := range nodes {
-			if node, ok := driver.nodes[nodeID]; ok == true {
-				bucketID := bucketName + ":0:" + strconv.Itoa(i)
-				reader, err := node.GetReader(bucketID, objectName)
-				if err != nil {
-					return nil, err
-				}
-				readers[i] = reader
-				if metadata == nil {
-					metadata, err = node.GetDonutMetadata(bucketID, objectName)
-					if err != nil {
-						return nil, err
-					}
-				}
-			}
-		}
-		go erasureReader(readers, metadata, w)
-		return r, nil
-	}
-	return nil, errors.New("Bucket not found")
-}
-
-// GetObjectMetadata returns metadata for a given object in a bucket
-func (driver donutDriver) GetObjectMetadata(bucketName, object string) (map[string]string, error) {
-	if bucket, ok := driver.buckets[bucketName]; ok {
-		nodes, err := bucket.GetNodes()
-		if err != nil {
-			return nil, err
-		}
-		if node, ok := driver.nodes[nodes[0]]; ok {
-			bucketID := bucketName + ":0:0"
-			metadata, err := node.GetMetadata(bucketID, object)
-			if err != nil {
-				return nil, err
-			}
-			donutMetadata, err := node.GetDonutMetadata(bucketID, object)
-			if err != nil {
-				return nil, err
-			}
-			metadata["sys.created"] = donutMetadata["created"]
-			metadata["sys.md5"] = donutMetadata["md5"]
-			metadata["sys.size"] = donutMetadata["size"]
-			return metadata, nil
-		}
-		return nil, errors.New("Cannot connect to node: " + nodes[0])
-	}
-	return nil, errors.New("Bucket not found")
-}
-
-func (driver donutDriver) ListObjects(bucketName string) ([]string, error) {
-	if bucket, ok := driver.buckets[bucketName]; ok {
-		nodes, err := bucket.GetNodes()
-		if err != nil {
-			return nil, err
-		}
-		if node, ok := driver.nodes[nodes[0]]; ok {
-			return node.ListObjects(bucketName + ":0:0")
-		}
-	}
-	return nil, errors.New("Bucket not found")
-}

pkg/storage/donut/erasure.go

@@ -14,6 +14,7 @@ import (
 	"strings"
 )
 
+// erasureReader - returns aligned streaming reads over a PipeWriter
 func erasureReader(readers []io.ReadCloser, donutMetadata map[string]string, writer *io.PipeWriter) {
 	// TODO handle errors
 	totalChunks, _ := strconv.Atoi(donutMetadata["chunkCount"])
@@ -70,6 +71,7 @@ type erasureWriter struct {
 	isClosed      <-chan bool
 }
 
+// newErasureWriter - get a new writer
 func newErasureWriter(writers []Writer) ObjectWriter {
 	r, w := io.Pipe()
 	isClosed := make(chan bool)

pkg/storage/donut/interfaces.go

@@ -0,0 +1,50 @@
+package donut
+
+import (
+	"io"
+)
+
+// Collection of Donut specification interfaces
+
+// Donut interface
+type Donut interface {
+	CreateBucket(bucket string) error
+	GetObjectReader(bucket, object string) (io.ReadCloser, error)
+	GetObjectWriter(bucket, object string) (ObjectWriter, error)
+	GetObjectMetadata(bucket, object string) (map[string]string, error)
+	ListBuckets() ([]string, error)
+	ListObjects(bucket string) ([]string, error)
+}
+
+// Bucket interface
+type Bucket interface {
+	GetNodes() ([]string, error)
+}
+
+// Node interface
+type Node interface {
+	CreateBucket(bucket string) error
+	GetBuckets() ([]string, error)
+	GetDonutMetadata(bucket, object string) (map[string]string, error)
+	GetMetadata(bucket, object string) (map[string]string, error)
+	GetReader(bucket, object string) (io.ReadCloser, error)
+	GetWriter(bucket, object string) (Writer, error)
+	ListObjects(bucket string) ([]string, error)
+}
+
+// ObjectWriter interface
+type ObjectWriter interface {
+	Close() error
+	CloseWithError(error) error
+	GetMetadata() (map[string]string, error)
+	SetMetadata(map[string]string) error
+	Write([]byte) (int, error)
+}
+
+// Writer interface
+type Writer interface {
+	ObjectWriter
+
+	GetDonutMetadata() (map[string]string, error)
+	SetDonutMetadata(map[string]string) error
+}

pkg/storage/donut/node_local.go

@@ -31,7 +31,7 @@ func (d localDirectoryNode) GetWriter(bucket, object string) (Writer, error) {
 	if err != nil {
 		return nil, err
 	}
-	return newDonutFileWriter(objectPath)
+	return newDonutObjectWriter(objectPath)
 }
 
 func (d localDirectoryNode) GetReader(bucket, object string) (io.ReadCloser, error) {

pkg/storage/donut/object_writer.go

@@ -7,12 +7,12 @@ import (
 	"path"
 )
 
-func newDonutFileWriter(objectDir string) (Writer, error) {
+func newDonutObjectWriter(objectDir string) (Writer, error) {
 	dataFile, err := os.OpenFile(path.Join(objectDir, "data"), os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
 	if err != nil {
 		return nil, err
 	}
-	return donutFileWriter{
+	return donutObjectWriter{
 		root:          objectDir,
 		file:          dataFile,
 		metadata:      make(map[string]string),
@@ -20,7 +20,7 @@ func newDonutFileWriter(objectDir string) (Writer, error) {
 	}, nil
 }
 
-type donutFileWriter struct {
+type donutObjectWriter struct {
 	root          string
 	file          *os.File
 	metadata      map[string]string
@@ -28,11 +28,11 @@ type donutFileWriter struct {
 	err           error
 }
 
-func (d donutFileWriter) Write(data []byte) (int, error) {
+func (d donutObjectWriter) Write(data []byte) (int, error) {
 	return d.file.Write(data)
 }
 
-func (d donutFileWriter) Close() error {
+func (d donutObjectWriter) Close() error {
 	if d.err != nil {
 		return d.err
 	}
@@ -44,14 +44,14 @@ func (d donutFileWriter) Close() error {
 	return d.file.Close()
 }
 
-func (d donutFileWriter) CloseWithError(err error) error {
+func (d donutObjectWriter) CloseWithError(err error) error {
 	if d.err != nil {
 		d.err = err
 	}
 	return d.Close()
 }
 
-func (d donutFileWriter) SetMetadata(metadata map[string]string) error {
+func (d donutObjectWriter) SetMetadata(metadata map[string]string) error {
 	for k := range d.metadata {
 		delete(d.metadata, k)
 	}
@@ -61,7 +61,7 @@ func (d donutFileWriter) SetMetadata(metadata map[string]string) error {
 	return nil
 }
 
-func (d donutFileWriter) GetMetadata() (map[string]string, error) {
+func (d donutObjectWriter) GetMetadata() (map[string]string, error) {
 	metadata := make(map[string]string)
 	for k, v := range d.metadata {
 		metadata[k] = v
@@ -69,7 +69,7 @@ func (d donutFileWriter) GetMetadata() (map[string]string, error) {
 	return metadata, nil
 }
 
-func (d donutFileWriter) SetDonutMetadata(metadata map[string]string) error {
+func (d donutObjectWriter) SetDonutMetadata(metadata map[string]string) error {
 	for k := range d.donutMetadata {
 		delete(d.donutMetadata, k)
 	}
@@ -79,7 +79,7 @@ func (d donutFileWriter) SetDonutMetadata(metadata map[string]string) error {
 	return nil
 }
 
-func (d donutFileWriter) GetDonutMetadata() (map[string]string, error) {
+func (d donutObjectWriter) GetDonutMetadata() (map[string]string, error) {
 	donutMetadata := make(map[string]string)
 	for k, v := range d.donutMetadata {
 		donutMetadata[k] = v

pkg/storage/donut/objectwriter.go

@@ -1,39 +0,0 @@
-package donut
-
-import (
-	"errors"
-)
-
-type objectWriter struct {
-	metadata map[string]string
-}
-
-func (obj objectWriter) Write(data []byte) (length int, err error) {
-	return 11, nil
-}
-
-func (obj objectWriter) Close() error {
-	return nil
-}
-
-func (obj objectWriter) CloseWithError(err error) error {
-	return errors.New("Not Implemented")
-}
-
-func (obj objectWriter) SetMetadata(metadata map[string]string) error {
-	for k := range obj.metadata {
-		delete(obj.metadata, k)
-	}
-	for k, v := range metadata {
-		obj.metadata[k] = v
-	}
-	return nil
-}
-
-func (obj objectWriter) GetMetadata() (map[string]string, error) {
-	ret := make(map[string]string)
-	for k, v := range obj.metadata {
-		ret[k] = v
-	}
-	return ret, nil
-}