Merge pull request #76 from ahmetalpbalkan/azure-fixes

storagedriver/azure: fix azure storage driver methods, implement Stat

Godeps/Godeps.json

@@ -22,6 +22,11 @@
 			"ImportPath": "github.com/AdRoll/goamz/s3",
 			"Rev": "d3664b76d90508cdda5a6c92042f26eab5db3103"
 		},
+		{
+			"ImportPath": "github.com/MSOpenTech/azure-sdk-for-go/clients/storage",
+			"Comment": "v1.1-119-g0fbd371",
+			"Rev": "0fbd37144de3adc2aef74db867c0e15e41c7f74a"
+		},
 		{
 			"ImportPath": "github.com/Sirupsen/logrus",
 			"Comment": "v0.6.4-12-g467d9d5",

Godeps/_workspace/src/github.com/MSOpenTech/azure-sdk-for-go/clients/storage/blob.go

@@ -0,0 +1,884 @@
+package storage
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type BlobStorageClient struct {
+	client StorageClient
+}
+
+// A Container is an entry in ContainerListResponse.
+type Container struct {
+	Name       string              `xml:"Name"`
+	Properties ContainerProperties `xml:"Properties"`
+	// TODO (ahmetalpbalkan) Metadata
+}
+
+// ContainerProperties contains various properties of a
+// container returned from various endpoints like ListContainers.
+type ContainerProperties struct {
+	LastModified  string `xml:"Last-Modified"`
+	Etag          string `xml:"Etag"`
+	LeaseStatus   string `xml:"LeaseStatus"`
+	LeaseState    string `xml:"LeaseState"`
+	LeaseDuration string `xml:"LeaseDuration"`
+	// TODO (ahmetalpbalkan) remaining fields
+}
+
+// ContainerListResponse contains the response fields from
+// ListContainers call. https://msdn.microsoft.com/en-us/library/azure/dd179352.aspx
+type ContainerListResponse struct {
+	XMLName    xml.Name    `xml:"EnumerationResults"`
+	Xmlns      string      `xml:"xmlns,attr"`
+	Prefix     string      `xml:"Prefix"`
+	Marker     string      `xml:"Marker"`
+	NextMarker string      `xml:"NextMarker"`
+	MaxResults int64       `xml:"MaxResults"`
+	Containers []Container `xml:"Containers>Container"`
+}
+
+// A Blob is an entry in BlobListResponse.
+type Blob struct {
+	Name       string         `xml:"Name"`
+	Properties BlobProperties `xml:"Properties"`
+	// TODO (ahmetalpbalkan) Metadata
+}
+
+// BlobProperties contains various properties of a blob
+// returned in various endpoints like ListBlobs or GetBlobProperties.
+type BlobProperties struct {
+	LastModified          string   `xml:"Last-Modified"`
+	Etag                  string   `xml:"Etag"`
+	ContentMD5            string   `xml:"Content-MD5"`
+	ContentLength         int64    `xml:"Content-Length"`
+	ContentType           string   `xml:"Content-Type"`
+	ContentEncoding       string   `xml:"Content-Encoding"`
+	BlobType              BlobType `xml:"x-ms-blob-blob-type"`
+	SequenceNumber        int64    `xml:"x-ms-blob-sequence-number"`
+	CopyId                string   `xml:"CopyId"`
+	CopyStatus            string   `xml:"CopyStatus"`
+	CopySource            string   `xml:"CopySource"`
+	CopyProgress          string   `xml:"CopyProgress"`
+	CopyCompletionTime    string   `xml:"CopyCompletionTime"`
+	CopyStatusDescription string   `xml:"CopyStatusDescription"`
+}
+
+// BlobListResponse contains the response fields from
+// ListBlobs call. https://msdn.microsoft.com/en-us/library/azure/dd135734.aspx
+type BlobListResponse struct {
+	XMLName    xml.Name `xml:"EnumerationResults"`
+	Xmlns      string   `xml:"xmlns,attr"`
+	Prefix     string   `xml:"Prefix"`
+	Marker     string   `xml:"Marker"`
+	NextMarker string   `xml:"NextMarker"`
+	MaxResults int64    `xml:"MaxResults"`
+	Blobs      []Blob   `xml:"Blobs>Blob"`
+}
+
+// ListContainersParameters defines the set of customizable
+// parameters to make a List Containers call. https://msdn.microsoft.com/en-us/library/azure/dd179352.aspx
+type ListContainersParameters struct {
+	Prefix     string
+	Marker     string
+	Include    string
+	MaxResults uint
+	Timeout    uint
+}
+
+func (p ListContainersParameters) getParameters() url.Values {
+	out := url.Values{}
+
+	if p.Prefix != "" {
+		out.Set("prefix", p.Prefix)
+	}
+	if p.Marker != "" {
+		out.Set("marker", p.Marker)
+	}
+	if p.Include != "" {
+		out.Set("include", p.Include)
+	}
+	if p.MaxResults != 0 {
+		out.Set("maxresults", fmt.Sprintf("%v", p.MaxResults))
+	}
+	if p.Timeout != 0 {
+		out.Set("timeout", fmt.Sprintf("%v", p.Timeout))
+	}
+
+	return out
+}
+
+// ListBlobsParameters defines the set of customizable
+// parameters to make a List Blobs call. https://msdn.microsoft.com/en-us/library/azure/dd135734.aspx
+type ListBlobsParameters struct {
+	Prefix     string
+	Delimiter  string
+	Marker     string
+	Include    string
+	MaxResults uint
+	Timeout    uint
+}
+
+func (p ListBlobsParameters) getParameters() url.Values {
+	out := url.Values{}
+
+	if p.Prefix != "" {
+		out.Set("prefix", p.Prefix)
+	}
+	if p.Delimiter != "" {
+		out.Set("delimiter", p.Delimiter)
+	}
+	if p.Marker != "" {
+		out.Set("marker", p.Marker)
+	}
+	if p.Include != "" {
+		out.Set("include", p.Include)
+	}
+	if p.MaxResults != 0 {
+		out.Set("maxresults", fmt.Sprintf("%v", p.MaxResults))
+	}
+	if p.Timeout != 0 {
+		out.Set("timeout", fmt.Sprintf("%v", p.Timeout))
+	}
+
+	return out
+}
+
+// BlobType defines the type of the Azure Blob.
+type BlobType string
+
+const (
+	BlobTypeBlock BlobType = "BlockBlob"
+	BlobTypePage  BlobType = "PageBlob"
+)
+
+// PageWriteType defines the type updates that are going to be
+// done on the page blob.
+type PageWriteType string
+
+const (
+	PageWriteTypeUpdate PageWriteType = "update"
+	PageWriteTypeClear  PageWriteType = "clear"
+)
+
+const (
+	blobCopyStatusPending = "pending"
+	blobCopyStatusSuccess = "success"
+	blobCopyStatusAborted = "aborted"
+	blobCopyStatusFailed  = "failed"
+)
+
+// BlockListType is used to filter out types of blocks
+// in a Get Blocks List call for a block blob. See
+// https://msdn.microsoft.com/en-us/library/azure/dd179400.aspx
+// for all block types.
+type BlockListType string
+
+const (
+	BlockListTypeAll         BlockListType = "all"
+	BlockListTypeCommitted   BlockListType = "committed"
+	BlockListTypeUncommitted BlockListType = "uncommitted"
+)
+
+// ContainerAccessType defines the access level to the container
+// from a public request. See https://msdn.microsoft.com/en-us/library/azure/dd179468.aspx
+// and "x-ms-blob-public-access" header.
+type ContainerAccessType string
+
+const (
+	ContainerAccessTypePrivate   ContainerAccessType = ""
+	ContainerAccessTypeBlob      ContainerAccessType = "blob"
+	ContainerAccessTypeContainer ContainerAccessType = "container"
+)
+
+const (
+	MaxBlobBlockSize = 4 * 1024 * 1024
+	MaxBlobPageSize  = 4 * 1024 * 1024
+)
+
+// BlockStatus defines states a block for a block blob can
+// be in.
+type BlockStatus string
+
+const (
+	BlockStatusUncommitted BlockStatus = "Uncommitted"
+	BlockStatusCommitted   BlockStatus = "Committed"
+	BlockStatusLatest      BlockStatus = "Latest"
+)
+
+// Block is used to create Block entities for Put Block List
+// call.
+type Block struct {
+	Id     string
+	Status BlockStatus
+}
+
+// BlockListResponse contains the response fields from
+// Get Block List call. https://msdn.microsoft.com/en-us/library/azure/dd179400.aspx
+type BlockListResponse struct {
+	XMLName           xml.Name        `xml:"BlockList"`
+	CommittedBlocks   []BlockResponse `xml:"CommittedBlocks>Block"`
+	UncommittedBlocks []BlockResponse `xml:"UncommittedBlocks>Block"`
+}
+
+// BlockResponse contains the block information returned
+// in the GetBlockListCall.
+type BlockResponse struct {
+	Name string `xml:"Name"`
+	Size int64  `xml:"Size"`
+}
+
+// GetPageRangesResponse contains the reponse fields from
+// Get Page Ranges call. https://msdn.microsoft.com/en-us/library/azure/ee691973.aspx
+type GetPageRangesResponse struct {
+	XMLName  xml.Name    `xml:"PageList"`
+	PageList []PageRange `xml:"PageRange"`
+}
+
+// PageRange contains information about a page of a page blob from
+// Get Pages Range call. https://msdn.microsoft.com/en-us/library/azure/ee691973.aspx
+type PageRange struct {
+	Start int64 `xml:"Start"`
+	End   int64 `xml:"End"`
+}
+
+var (
+	ErrNotCreated  = errors.New("storage: operation has returned a successful error code other than 201 Created.")
+	ErrNotAccepted = errors.New("storage: operation has returned a successful error code other than 202 Accepted.")
+
+	errBlobCopyAborted    = errors.New("storage: blob copy is aborted")
+	errBlobCopyIdMismatch = errors.New("storage: blob copy id is a mismatch")
+)
+
+const errUnexpectedStatus = "storage: was expecting status code: %d, got: %d"
+
+// ListContainers returns the list of containers in a storage account along with
+// pagination token and other response details. See https://msdn.microsoft.com/en-us/library/azure/dd179352.aspx
+func (b BlobStorageClient) ListContainers(params ListContainersParameters) (ContainerListResponse, error) {
+	q := mergeParams(params.getParameters(), url.Values{"comp": {"list"}})
+	uri := b.client.getEndpoint(blobServiceName, "", q)
+	headers := b.client.getStandardHeaders()
+
+	var out ContainerListResponse
+	resp, err := b.client.exec("GET", uri, headers, nil)
+	if err != nil {
+		return out, err
+	}
+
+	err = xmlUnmarshal(resp.body, &out)
+	return out, err
+}
+
+// CreateContainer creates a blob container within the storage account
+// with given name and access level. See https://msdn.microsoft.com/en-us/library/azure/dd179468.aspx
+// Returns error if container already exists.
+func (b BlobStorageClient) CreateContainer(name string, access ContainerAccessType) error {
+	resp, err := b.createContainer(name, access)
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusCreated {
+		return ErrNotCreated
+	}
+	return nil
+}
+
+// CreateContainerIfNotExists creates a blob container if it does not exist. Returns
+// true if container is newly created or false if container already exists.
+func (b BlobStorageClient) CreateContainerIfNotExists(name string, access ContainerAccessType) (bool, error) {
+	resp, err := b.createContainer(name, access)
+	if resp != nil && (resp.statusCode == http.StatusCreated || resp.statusCode == http.StatusConflict) {
+		return resp.statusCode == http.StatusCreated, nil
+	}
+	return false, err
+}
+
+func (b BlobStorageClient) createContainer(name string, access ContainerAccessType) (*storageResponse, error) {
+	verb := "PUT"
+	uri := b.client.getEndpoint(blobServiceName, pathForContainer(name), url.Values{"restype": {"container"}})
+
+	headers := b.client.getStandardHeaders()
+	headers["Content-Length"] = "0"
+	if access != "" {
+		headers["x-ms-blob-public-access"] = string(access)
+	}
+	return b.client.exec(verb, uri, headers, nil)
+}
+
+// ContainerExists returns true if a container with given name exists
+// on the storage account, otherwise returns false.
+func (b BlobStorageClient) ContainerExists(name string) (bool, error) {
+	verb := "HEAD"
+	uri := b.client.getEndpoint(blobServiceName, pathForContainer(name), url.Values{"restype": {"container"}})
+	headers := b.client.getStandardHeaders()
+
+	resp, err := b.client.exec(verb, uri, headers, nil)
+	if resp != nil && (resp.statusCode == http.StatusOK || resp.statusCode == http.StatusNotFound) {
+		return resp.statusCode == http.StatusOK, nil
+	}
+	return false, err
+}
+
+// DeleteContainer deletes the container with given name on the storage
+// account. See https://msdn.microsoft.com/en-us/library/azure/dd179408.aspx
+// If the container does not exist returns error.
+func (b BlobStorageClient) DeleteContainer(name string) error {
+	resp, err := b.deleteContainer(name)
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusAccepted {
+		return ErrNotAccepted
+	}
+	return nil
+}
+
+// DeleteContainer deletes the container with given name on the storage
+// account if it exists. See https://msdn.microsoft.com/en-us/library/azure/dd179408.aspx
+// Returns true if container is deleted with this call, or false
+// if the container did not exist at the time of the Delete Container operation.
+func (b BlobStorageClient) DeleteContainerIfExists(name string) (bool, error) {
+	resp, err := b.deleteContainer(name)
+	if resp != nil && (resp.statusCode == http.StatusAccepted || resp.statusCode == http.StatusNotFound) {
+		return resp.statusCode == http.StatusAccepted, nil
+	}
+	return false, err
+}
+
+func (b BlobStorageClient) deleteContainer(name string) (*storageResponse, error) {
+	verb := "DELETE"
+	uri := b.client.getEndpoint(blobServiceName, pathForContainer(name), url.Values{"restype": {"container"}})
+
+	headers := b.client.getStandardHeaders()
+	return b.client.exec(verb, uri, headers, nil)
+}
+
+// ListBlobs returns an object that contains list of blobs in the container,
+// pagination token and other information in the response of List Blobs call.
+// See https://msdn.microsoft.com/en-us/library/azure/dd135734.aspx
+func (b BlobStorageClient) ListBlobs(container string, params ListBlobsParameters) (BlobListResponse, error) {
+	q := mergeParams(params.getParameters(), url.Values{
+		"restype": {"container"},
+		"comp":    {"list"}})
+	uri := b.client.getEndpoint(blobServiceName, pathForContainer(container), q)
+	headers := b.client.getStandardHeaders()
+
+	var out BlobListResponse
+	resp, err := b.client.exec("GET", uri, headers, nil)
+	if err != nil {
+		return out, err
+	}
+
+	err = xmlUnmarshal(resp.body, &out)
+	return out, err
+}
+
+// BlobExists returns true if a blob with given name exists on the
+// specified container of the storage account.
+func (b BlobStorageClient) BlobExists(container, name string) (bool, error) {
+	verb := "HEAD"
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{})
+
+	headers := b.client.getStandardHeaders()
+	resp, err := b.client.exec(verb, uri, headers, nil)
+	if resp != nil && (resp.statusCode == http.StatusOK || resp.statusCode == http.StatusNotFound) {
+		return resp.statusCode == http.StatusOK, nil
+	}
+	return false, err
+}
+
+// GetBlobUrl gets the canonical URL to the blob with the specified
+// name in the specified container. This method does not create a
+// publicly accessible URL if the blob or container is private and this
+// method does not check if the blob exists.
+func (b BlobStorageClient) GetBlobUrl(container, name string) string {
+	if container == "" {
+		container = "$root"
+	}
+	return b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{})
+}
+
+// GetBlob downloads a blob to a stream. See https://msdn.microsoft.com/en-us/library/azure/dd179440.aspx
+func (b BlobStorageClient) GetBlob(container, name string) (io.ReadCloser, error) {
+	resp, err := b.getBlobRange(container, name, "")
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.statusCode != http.StatusOK {
+		return nil, fmt.Errorf(errUnexpectedStatus, http.StatusOK, resp.statusCode)
+	}
+	return resp.body, nil
+}
+
+// GetBlobRange reads the specified range of a blob to a stream.
+// The bytesRange string must be in a format like "0-", "10-100"
+// as defined in HTTP 1.1 spec. See https://msdn.microsoft.com/en-us/library/azure/dd179440.aspx
+func (b BlobStorageClient) GetBlobRange(container, name, bytesRange string) (io.ReadCloser, error) {
+	resp, err := b.getBlobRange(container, name, bytesRange)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.statusCode != http.StatusPartialContent {
+		return nil, fmt.Errorf(errUnexpectedStatus, http.StatusPartialContent, resp.statusCode)
+	}
+	return resp.body, nil
+}
+
+func (b BlobStorageClient) getBlobRange(container, name, bytesRange string) (*storageResponse, error) {
+	verb := "GET"
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{})
+
+	headers := b.client.getStandardHeaders()
+	if bytesRange != "" {
+		headers["Range"] = fmt.Sprintf("bytes=%s", bytesRange)
+	}
+	resp, err := b.client.exec(verb, uri, headers, nil)
+	if err != nil {
+		return nil, err
+	}
+	return resp, err
+}
+
+// GetBlobProperties provides various information about the specified
+// blob. See https://msdn.microsoft.com/en-us/library/azure/dd179394.aspx
+func (b BlobStorageClient) GetBlobProperties(container, name string) (*BlobProperties, error) {
+	verb := "HEAD"
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{})
+
+	headers := b.client.getStandardHeaders()
+	resp, err := b.client.exec(verb, uri, headers, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.statusCode != http.StatusOK {
+		return nil, fmt.Errorf(errUnexpectedStatus, http.StatusOK, resp.statusCode)
+	}
+
+	var contentLength int64
+	contentLengthStr := resp.headers.Get("Content-Length")
+	if contentLengthStr != "" {
+		contentLength, err = strconv.ParseInt(contentLengthStr, 0, 64)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	var sequenceNum int64
+	sequenceNumStr := resp.headers.Get("x-ms-blob-sequence-number")
+	if sequenceNumStr != "" {
+		sequenceNum, err = strconv.ParseInt(sequenceNumStr, 0, 64)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return &BlobProperties{
+		LastModified:          resp.headers.Get("Last-Modified"),
+		Etag:                  resp.headers.Get("Etag"),
+		ContentMD5:            resp.headers.Get("Content-MD5"),
+		ContentLength:         contentLength,
+		ContentEncoding:       resp.headers.Get("Content-Encoding"),
+		SequenceNumber:        sequenceNum,
+		CopyCompletionTime:    resp.headers.Get("x-ms-copy-completion-time"),
+		CopyStatusDescription: resp.headers.Get("x-ms-copy-status-description"),
+		CopyId:                resp.headers.Get("x-ms-copy-id"),
+		CopyProgress:          resp.headers.Get("x-ms-copy-progress"),
+		CopySource:            resp.headers.Get("x-ms-copy-source"),
+		CopyStatus:            resp.headers.Get("x-ms-copy-status"),
+		BlobType:              BlobType(resp.headers.Get("x-ms-blob-type")),
+	}, nil
+}
+
+// CreateBlockBlob initializes an empty block blob with no blocks.
+// See https://msdn.microsoft.com/en-us/library/azure/dd179451.aspx
+func (b BlobStorageClient) CreateBlockBlob(container, name string) error {
+	path := fmt.Sprintf("%s/%s", container, name)
+	uri := b.client.getEndpoint(blobServiceName, path, url.Values{})
+	headers := b.client.getStandardHeaders()
+	headers["x-ms-blob-type"] = string(BlobTypeBlock)
+	headers["Content-Length"] = fmt.Sprintf("%v", 0)
+
+	resp, err := b.client.exec("PUT", uri, headers, nil)
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusCreated {
+		return ErrNotCreated
+	}
+	return nil
+}
+
+// PutBlockBlob uploads given stream into a block blob by splitting
+// data stream into chunks and uploading as blocks. Commits the block
+// list at the end. This is a helper method built on top of PutBlock
+// and PutBlockList methods with sequential block ID counting logic.
+func (b BlobStorageClient) PutBlockBlob(container, name string, blob io.Reader) error { // TODO (ahmetalpbalkan) consider ReadCloser and closing
+	return b.putBlockBlob(container, name, blob, MaxBlobBlockSize)
+}
+
+func (b BlobStorageClient) putBlockBlob(container, name string, blob io.Reader, chunkSize int) error {
+	if chunkSize <= 0 || chunkSize > MaxBlobBlockSize {
+		chunkSize = MaxBlobBlockSize
+	}
+
+	chunk := make([]byte, chunkSize)
+	n, err := blob.Read(chunk)
+	if err != nil && err != io.EOF {
+		return err
+	}
+
+	if err == io.EOF {
+		// Fits into one block
+		return b.putSingleBlockBlob(container, name, chunk[:n])
+	} else {
+		// Does not fit into one block. Upload block by block then commit the block list
+		blockList := []Block{}
+
+		// Put blocks
+		for blockNum := 0; ; blockNum++ {
+			id := base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%011d", blockNum)))
+			data := chunk[:n]
+			err = b.PutBlock(container, name, id, data)
+			if err != nil {
+				return err
+			}
+			blockList = append(blockList, Block{id, BlockStatusLatest})
+
+			// Read next block
+			n, err = blob.Read(chunk)
+			if err != nil && err != io.EOF {
+				return err
+			}
+			if err == io.EOF {
+				break
+			}
+		}
+
+		// Commit block list
+		return b.PutBlockList(container, name, blockList)
+	}
+}
+
+func (b BlobStorageClient) putSingleBlockBlob(container, name string, chunk []byte) error {
+	if len(chunk) > MaxBlobBlockSize {
+		return fmt.Errorf("storage: provided chunk (%d bytes) cannot fit into single-block blob (max %d bytes)", len(chunk), MaxBlobBlockSize)
+	}
+
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{})
+	headers := b.client.getStandardHeaders()
+	headers["x-ms-blob-type"] = string(BlobTypeBlock)
+	headers["Content-Length"] = fmt.Sprintf("%v", len(chunk))
+
+	resp, err := b.client.exec("PUT", uri, headers, bytes.NewReader(chunk))
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusCreated {
+		return ErrNotCreated
+	}
+
+	return nil
+}
+
+// PutBlock saves the given data chunk to the specified block blob with
+// given ID. See https://msdn.microsoft.com/en-us/library/azure/dd135726.aspx
+func (b BlobStorageClient) PutBlock(container, name, blockId string, chunk []byte) error {
+	return b.PutBlockWithLength(container, name, blockId, uint64(len(chunk)), bytes.NewReader(chunk))
+}
+
+// PutBlockWithLength saves the given data stream of exactly specified size to the block blob
+// with given ID. See https://msdn.microsoft.com/en-us/library/azure/dd135726.aspx
+// It is an alternative to PutBlocks where data comes as stream but the length is
+// known in advance.
+func (b BlobStorageClient) PutBlockWithLength(container, name, blockId string, size uint64, blob io.Reader) error {
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{"comp": {"block"}, "blockid": {blockId}})
+	headers := b.client.getStandardHeaders()
+	headers["x-ms-blob-type"] = string(BlobTypeBlock)
+	headers["Content-Length"] = fmt.Sprintf("%v", size)
+
+	resp, err := b.client.exec("PUT", uri, headers, blob)
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusCreated {
+		return ErrNotCreated
+	}
+
+	return nil
+}
+
+// PutBlockList saves list of blocks to the specified block blob. See
+// https://msdn.microsoft.com/en-us/library/azure/dd179467.aspx
+func (b BlobStorageClient) PutBlockList(container, name string, blocks []Block) error {
+	blockListXml := prepareBlockListRequest(blocks)
+
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{"comp": {"blocklist"}})
+	headers := b.client.getStandardHeaders()
+	headers["Content-Length"] = fmt.Sprintf("%v", len(blockListXml))
+
+	resp, err := b.client.exec("PUT", uri, headers, strings.NewReader(blockListXml))
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusCreated {
+		return ErrNotCreated
+	}
+	return nil
+}
+
+// GetBlockList retrieves list of blocks in the specified block blob. See
+// https://msdn.microsoft.com/en-us/library/azure/dd179400.aspx
+func (b BlobStorageClient) GetBlockList(container, name string, blockType BlockListType) (BlockListResponse, error) {
+	params := url.Values{"comp": {"blocklist"}, "blocklisttype": {string(blockType)}}
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), params)
+	headers := b.client.getStandardHeaders()
+
+	var out BlockListResponse
+	resp, err := b.client.exec("GET", uri, headers, nil)
+	if err != nil {
+		return out, err
+	}
+
+	err = xmlUnmarshal(resp.body, &out)
+	return out, err
+}
+
+// PutPageBlob initializes an empty page blob with specified name and maximum
+// size in bytes (size must be aligned to a 512-byte boundary). A page blob must
+// be created using this method before writing pages.
+// See https://msdn.microsoft.com/en-us/library/azure/dd179451.aspx
+func (b BlobStorageClient) PutPageBlob(container, name string, size int64) error {
+	path := fmt.Sprintf("%s/%s", container, name)
+	uri := b.client.getEndpoint(blobServiceName, path, url.Values{})
+	headers := b.client.getStandardHeaders()
+	headers["x-ms-blob-type"] = string(BlobTypePage)
+	headers["x-ms-blob-content-length"] = fmt.Sprintf("%v", size)
+	headers["Content-Length"] = fmt.Sprintf("%v", 0)
+
+	resp, err := b.client.exec("PUT", uri, headers, nil)
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusCreated {
+		return ErrNotCreated
+	}
+	return nil
+}
+
+// PutPage writes a range of pages to a page blob or clears the given range.
+// In case of 'clear' writes, given chunk is discarded. Ranges must be aligned
+// with 512-byte boundaries and chunk must be of size multiplies by 512.
+// See https://msdn.microsoft.com/en-us/library/ee691975.aspx
+func (b BlobStorageClient) PutPage(container, name string, startByte, endByte int64, writeType PageWriteType, chunk []byte) error {
+	path := fmt.Sprintf("%s/%s", container, name)
+	uri := b.client.getEndpoint(blobServiceName, path, url.Values{"comp": {"page"}})
+	headers := b.client.getStandardHeaders()
+	headers["x-ms-blob-type"] = string(BlobTypePage)
+	headers["x-ms-page-write"] = string(writeType)
+	headers["x-ms-range"] = fmt.Sprintf("bytes=%v-%v", startByte, endByte)
+
+	var contentLength int64
+	var data io.Reader
+	if writeType == PageWriteTypeClear {
+		contentLength = 0
+		data = bytes.NewReader([]byte{})
+	} else {
+		contentLength = int64(len(chunk))
+		data = bytes.NewReader(chunk)
+	}
+	headers["Content-Length"] = fmt.Sprintf("%v", contentLength)
+
+	resp, err := b.client.exec("PUT", uri, headers, data)
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusCreated {
+		return ErrNotCreated
+	}
+	return nil
+}
+
+// GetPageRanges returns the list of valid page ranges for a page blob.
+// See https://msdn.microsoft.com/en-us/library/azure/ee691973.aspx
+func (b BlobStorageClient) GetPageRanges(container, name string) (GetPageRangesResponse, error) {
+	path := fmt.Sprintf("%s/%s", container, name)
+	uri := b.client.getEndpoint(blobServiceName, path, url.Values{"comp": {"pagelist"}})
+	headers := b.client.getStandardHeaders()
+
+	var out GetPageRangesResponse
+	resp, err := b.client.exec("GET", uri, headers, nil)
+	if err != nil {
+		return out, err
+	}
+
+	if resp.statusCode != http.StatusOK {
+		return out, fmt.Errorf(errUnexpectedStatus, http.StatusOK, resp.statusCode)
+	}
+
+	err = xmlUnmarshal(resp.body, &out)
+	return out, err
+}
+
+// CopyBlob starts a blob copy operation and waits for the operation to complete.
+// sourceBlob parameter must be a canonical URL to the blob (can be obtained using
+// GetBlobURL method.) There is no SLA on blob copy and therefore this helper
+// method works faster on smaller files. See https://msdn.microsoft.com/en-us/library/azure/dd894037.aspx
+func (b BlobStorageClient) CopyBlob(container, name, sourceBlob string) error {
+	copyId, err := b.startBlobCopy(container, name, sourceBlob)
+	if err != nil {
+		return err
+	}
+
+	return b.waitForBlobCopy(container, name, copyId)
+}
+
+func (b BlobStorageClient) startBlobCopy(container, name, sourceBlob string) (string, error) {
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{})
+
+	headers := b.client.getStandardHeaders()
+	headers["Content-Length"] = "0"
+	headers["x-ms-copy-source"] = sourceBlob
+
+	resp, err := b.client.exec("PUT", uri, headers, nil)
+	if err != nil {
+		return "", err
+	}
+	if resp.statusCode != http.StatusAccepted && resp.statusCode != http.StatusCreated {
+		return "", fmt.Errorf(errUnexpectedStatus, []int{http.StatusAccepted, http.StatusCreated}, resp.statusCode)
+	}
+
+	copyId := resp.headers.Get("x-ms-copy-id")
+	if copyId == "" {
+		return "", errors.New("Got empty copy id header")
+	}
+	return copyId, nil
+}
+
+func (b BlobStorageClient) waitForBlobCopy(container, name, copyId string) error {
+	for {
+		props, err := b.GetBlobProperties(container, name)
+		if err != nil {
+			return err
+		}
+
+		if props.CopyId != copyId {
+			return errBlobCopyIdMismatch
+		}
+
+		switch props.CopyStatus {
+		case blobCopyStatusSuccess:
+			return nil
+		case blobCopyStatusPending:
+			continue
+		case blobCopyStatusAborted:
+			return errBlobCopyAborted
+		case blobCopyStatusFailed:
+			return fmt.Errorf("storage: blob copy failed. Id=%s Description=%s", props.CopyId, props.CopyStatusDescription)
+		default:
+			return fmt.Errorf("storage: unhandled blob copy status: '%s'", props.CopyStatus)
+		}
+	}
+}
+
+// DeleteBlob deletes the given blob from the specified container.
+// If the blob does not exists at the time of the Delete Blob operation, it
+// returns error. See https://msdn.microsoft.com/en-us/library/azure/dd179413.aspx
+func (b BlobStorageClient) DeleteBlob(container, name string) error {
+	resp, err := b.deleteBlob(container, name)
+	if err != nil {
+		return err
+	}
+	if resp.statusCode != http.StatusAccepted {
+		return ErrNotAccepted
+	}
+	return nil
+}
+
+// DeleteBlobIfExists deletes the given blob from the specified container
+// If the blob is deleted with this call, returns true. Otherwise returns
+// false. See https://msdn.microsoft.com/en-us/library/azure/dd179413.aspx
+func (b BlobStorageClient) DeleteBlobIfExists(container, name string) (bool, error) {
+	resp, err := b.deleteBlob(container, name)
+	if resp != nil && (resp.statusCode == http.StatusAccepted || resp.statusCode == http.StatusNotFound) {
+		return resp.statusCode == http.StatusAccepted, nil
+	}
+	return false, err
+}
+
+func (b BlobStorageClient) deleteBlob(container, name string) (*storageResponse, error) {
+	verb := "DELETE"
+	uri := b.client.getEndpoint(blobServiceName, pathForBlob(container, name), url.Values{})
+	headers := b.client.getStandardHeaders()
+
+	return b.client.exec(verb, uri, headers, nil)
+}
+
+// helper method to construct the path to a container given its name
+func pathForContainer(name string) string {
+	return fmt.Sprintf("/%s", name)
+}
+
+// helper method to construct the path to a blob given its container and blob name
+func pathForBlob(container, name string) string {
+	return fmt.Sprintf("/%s/%s", container, name)
+}
+
+// GetBlobSASURI creates an URL to the specified blob which contains the Shared Access Signature
+// with specified permissions and expiration time. See https://msdn.microsoft.com/en-us/library/azure/ee395415.aspx
+func (b BlobStorageClient) GetBlobSASURI(container, name string, expiry time.Time, permissions string) (string, error) {
+	var (
+		signedPermissions = permissions
+		blobUrl           = b.GetBlobUrl(container, name)
+	)
+	canonicalizedResource, err := b.client.buildCanonicalizedResource(blobUrl)
+	if err != nil {
+		return "", err
+	}
+	signedExpiry := expiry.Format(time.RFC3339)
+	signedResource := "b"
+
+	stringToSign, err := blobSASStringToSign(b.client.apiVersion, canonicalizedResource, signedExpiry, signedPermissions)
+	if err != nil {
+		return "", err
+	}
+
+	sig := b.client.computeHmac256(stringToSign)
+	sasParams := url.Values{
+		"sv":  {b.client.apiVersion},
+		"se":  {signedExpiry},
+		"sr":  {signedResource},
+		"sp":  {signedPermissions},
+		"sig": {sig},
+	}
+
+	sasUrl, err := url.Parse(blobUrl)
+	if err != nil {
+		return "", err
+	}
+	sasUrl.RawQuery = sasParams.Encode()
+	return sasUrl.String(), nil
+}
+
+func blobSASStringToSign(signedVersion, canonicalizedResource, signedExpiry, signedPermissions string) (string, error) {
+	var signedStart, signedIdentifier, rscc, rscd, rsce, rscl, rsct string
+
+	// reference: http://msdn.microsoft.com/en-us/library/azure/dn140255.aspx
+	if signedVersion >= "2013-08-15" {
+		return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s", signedPermissions, signedStart, signedExpiry, canonicalizedResource, signedIdentifier, signedVersion, rscc, rscd, rsce, rscl, rsct), nil
+	} else {
+		return "", errors.New("storage: not implemented SAS for versions earlier than 2013-08-15")
+	}
+}

Godeps/_workspace/src/github.com/MSOpenTech/azure-sdk-for-go/clients/storage/client.go

@@ -0,0 +1,315 @@
+package storage
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"regexp"
+	"sort"
+	"strings"
+)
+
+const (
+	DefaultBaseUrl    = "core.windows.net"
+	DefaultApiVersion = "2014-02-14"
+	defaultUseHttps   = true
+
+	blobServiceName  = "blob"
+	tableServiceName = "table"
+	queueServiceName = "queue"
+)
+
+// StorageClient is the object that needs to be constructed
+// to perform operations on the storage account.
+type StorageClient struct {
+	accountName string
+	accountKey  []byte
+	useHttps    bool
+	baseUrl     string
+	apiVersion  string
+}
+
+type storageResponse struct {
+	statusCode int
+	headers    http.Header
+	body       io.ReadCloser
+}
+
+// StorageServiceError contains fields of the error response from
+// Azure Storage Service REST API. See https://msdn.microsoft.com/en-us/library/azure/dd179382.aspx
+// Some fields might be specific to certain calls.
+type StorageServiceError struct {
+	Code                      string `xml:"Code"`
+	Message                   string `xml:"Message"`
+	AuthenticationErrorDetail string `xml:"AuthenticationErrorDetail"`
+	QueryParameterName        string `xml:"QueryParameterName"`
+	QueryParameterValue       string `xml:"QueryParameterValue"`
+	Reason                    string `xml:"Reason"`
+	StatusCode                int
+	RequestId                 string
+}
+
+// NewBasicClient constructs a StorageClient with given storage service name
+// and key.
+func NewBasicClient(accountName, accountKey string) (*StorageClient, error) {
+	return NewClient(accountName, accountKey, DefaultBaseUrl, DefaultApiVersion, defaultUseHttps)
+}
+
+// NewClient constructs a StorageClient. This should be used if the caller
+// wants to specify whether to use HTTPS, a specific REST API version or a
+// custom storage endpoint than Azure Public Cloud.
+func NewClient(accountName, accountKey, blobServiceBaseUrl, apiVersion string, useHttps bool) (*StorageClient, error) {
+	if accountName == "" {
+		return nil, fmt.Errorf("azure: account name required")
+	} else if accountKey == "" {
+		return nil, fmt.Errorf("azure: account key required")
+	} else if blobServiceBaseUrl == "" {
+		return nil, fmt.Errorf("azure: base storage service url required")
+	}
+
+	key, err := base64.StdEncoding.DecodeString(accountKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return &StorageClient{
+		accountName: accountName,
+		accountKey:  key,
+		useHttps:    useHttps,
+		baseUrl:     blobServiceBaseUrl,
+		apiVersion:  apiVersion}, nil
+}
+
+func (c StorageClient) getBaseUrl(service string) string {
+	scheme := "http"
+	if c.useHttps {
+		scheme = "https"
+	}
+
+	host := fmt.Sprintf("%s.%s.%s", c.accountName, service, c.baseUrl)
+
+	u := &url.URL{
+		Scheme: scheme,
+		Host:   host}
+	return u.String()
+}
+
+func (c StorageClient) getEndpoint(service, path string, params url.Values) string {
+	u, err := url.Parse(c.getBaseUrl(service))
+	if err != nil {
+		// really should not be happening
+		panic(err)
+	}
+
+	if path == "" {
+		path = "/" // API doesn't accept path segments not starting with '/'
+	}
+
+	u.Path = path
+	u.RawQuery = params.Encode()
+	return u.String()
+}
+
+// GetBlobService returns a BlobStorageClient which can operate on the
+// blob service of the storage account.
+func (c StorageClient) GetBlobService() *BlobStorageClient {
+	return &BlobStorageClient{c}
+}
+
+func (c StorageClient) createAuthorizationHeader(canonicalizedString string) string {
+	signature := c.computeHmac256(canonicalizedString)
+	return fmt.Sprintf("%s %s:%s", "SharedKey", c.accountName, signature)
+}
+
+func (c StorageClient) getAuthorizationHeader(verb, url string, headers map[string]string) (string, error) {
+	canonicalizedResource, err := c.buildCanonicalizedResource(url)
+	if err != nil {
+		return "", err
+	}
+
+	canonicalizedString := c.buildCanonicalizedString(verb, headers, canonicalizedResource)
+	return c.createAuthorizationHeader(canonicalizedString), nil
+}
+
+func (c StorageClient) getStandardHeaders() map[string]string {
+	return map[string]string{
+		"x-ms-version": c.apiVersion,
+		"x-ms-date":    currentTimeRfc1123Formatted(),
+	}
+}
+
+func (c StorageClient) buildCanonicalizedHeader(headers map[string]string) string {
+	cm := make(map[string]string)
+
+	for k, v := range headers {
+		headerName := strings.TrimSpace(strings.ToLower(k))
+		match, _ := regexp.MatchString("x-ms-", headerName)
+		if match {
+			cm[headerName] = v
+		}
+	}
+
+	if len(cm) == 0 {
+		return ""
+	}
+
+	keys := make([]string, 0, len(cm))
+	for key := range cm {
+		keys = append(keys, key)
+	}
+
+	sort.Strings(keys)
+
+	ch := ""
+
+	for i, key := range keys {
+		if i == len(keys)-1 {
+			ch += fmt.Sprintf("%s:%s", key, cm[key])
+		} else {
+			ch += fmt.Sprintf("%s:%s\n", key, cm[key])
+		}
+	}
+	return ch
+}
+
+func (c StorageClient) buildCanonicalizedResource(uri string) (string, error) {
+	errMsg := "buildCanonicalizedResource error: %s"
+	u, err := url.Parse(uri)
+	if err != nil {
+		return "", fmt.Errorf(errMsg, err.Error())
+	}
+
+	cr := "/" + c.accountName
+	if len(u.Path) > 0 {
+		cr += u.Path
+	}
+
+	params, err := url.ParseQuery(u.RawQuery)
+	if err != nil {
+		return "", fmt.Errorf(errMsg, err.Error())
+	}
+
+	if len(params) > 0 {
+		cr += "\n"
+		keys := make([]string, 0, len(params))
+		for key := range params {
+			keys = append(keys, key)
+		}
+
+		sort.Strings(keys)
+
+		for i, key := range keys {
+			if len(params[key]) > 1 {
+				sort.Strings(params[key])
+			}
+
+			if i == len(keys)-1 {
+				cr += fmt.Sprintf("%s:%s", key, strings.Join(params[key], ","))
+			} else {
+				cr += fmt.Sprintf("%s:%s\n", key, strings.Join(params[key], ","))
+			}
+		}
+	}
+	return cr, nil
+}
+
+func (c StorageClient) buildCanonicalizedString(verb string, headers map[string]string, canonicalizedResource string) string {
+	canonicalizedString := fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s",
+		verb,
+		headers["Content-Encoding"],
+		headers["Content-Language"],
+		headers["Content-Length"],
+		headers["Content-MD5"],
+		headers["Content-Type"],
+		headers["Date"],
+		headers["If-Modified-Singe"],
+		headers["If-Match"],
+		headers["If-None-Match"],
+		headers["If-Unmodified-Singe"],
+		headers["Range"],
+		c.buildCanonicalizedHeader(headers),
+		canonicalizedResource)
+
+	return canonicalizedString
+}
+
+func (c StorageClient) exec(verb, url string, headers map[string]string, body io.Reader) (*storageResponse, error) {
+	authHeader, err := c.getAuthorizationHeader(verb, url, headers)
+	if err != nil {
+		return nil, err
+	}
+	headers["Authorization"] = authHeader
+
+	if err != nil {
+		return nil, err
+	}
+
+	req, err := http.NewRequest(verb, url, body)
+	for k, v := range headers {
+		req.Header.Add(k, v)
+	}
+	httpClient := http.Client{}
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	statusCode := resp.StatusCode
+	if statusCode >= 400 && statusCode <= 505 {
+		var respBody []byte
+		respBody, err = readResponseBody(resp)
+		if err != nil {
+			return nil, err
+		}
+
+		if len(respBody) == 0 {
+			// no error in response body
+			err = fmt.Errorf("storage: service returned without a response body (%s).", resp.Status)
+		} else {
+			// response contains storage service error object, unmarshal
+			storageErr, errIn := serviceErrFromXml(respBody, resp.StatusCode, resp.Header.Get("x-ms-request-id"))
+			if err != nil { // error unmarshaling the error response
+				err = errIn
+			}
+			err = storageErr
+		}
+		return &storageResponse{
+			statusCode: resp.StatusCode,
+			headers:    resp.Header,
+			body:       ioutil.NopCloser(bytes.NewReader(respBody)), /* restore the body */
+		}, err
+	}
+
+	return &storageResponse{
+		statusCode: resp.StatusCode,
+		headers:    resp.Header,
+		body:       resp.Body}, nil
+}
+
+func readResponseBody(resp *http.Response) ([]byte, error) {
+	defer resp.Body.Close()
+	out, err := ioutil.ReadAll(resp.Body)
+	if err == io.EOF {
+		err = nil
+	}
+	return out, err
+}
+
+func serviceErrFromXml(body []byte, statusCode int, requestId string) (StorageServiceError, error) {
+	var storageErr StorageServiceError
+	if err := xml.Unmarshal(body, &storageErr); err != nil {
+		return storageErr, err
+	}
+	storageErr.StatusCode = statusCode
+	storageErr.RequestId = requestId
+	return storageErr, nil
+}
+
+func (e StorageServiceError) Error() string {
+	return fmt.Sprintf("storage: remote server returned error. StatusCode=%d, ErrorCode=%s, ErrorMessage=%s, RequestId=%s", e.StatusCode, e.Code, e.Message, e.RequestId)
+}

Godeps/_workspace/src/github.com/MSOpenTech/azure-sdk-for-go/clients/storage/client_test.go

@@ -0,0 +1,203 @@
+package storage
+
+import (
+	"encoding/base64"
+	"net/url"
+	"testing"
+)
+
+func TestGetBaseUrl_Basic_Https(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if cli.apiVersion != DefaultApiVersion {
+		t.Fatalf("Wrong api version. Expected: '%s', got: '%s'", DefaultApiVersion, cli.apiVersion)
+	}
+
+	if err != nil {
+		t.Fatal(err)
+	}
+	output := cli.getBaseUrl("table")
+
+	if expected := "https://foo.table.core.windows.net"; output != expected {
+		t.Fatalf("Wrong base url. Expected: '%s', got: '%s'", expected, output)
+	}
+}
+
+func TestGetBaseUrl_Custom_NoHttps(t *testing.T) {
+	apiVersion := DefaultApiVersion
+	cli, err := NewClient("foo", "YmFy", "core.chinacloudapi.cn", apiVersion, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if cli.apiVersion != apiVersion {
+		t.Fatalf("Wrong api version. Expected: '%s', got: '%s'", apiVersion, cli.apiVersion)
+	}
+
+	output := cli.getBaseUrl("table")
+
+	if expected := "http://foo.table.core.chinacloudapi.cn"; output != expected {
+		t.Fatalf("Wrong base url. Expected: '%s', got: '%s'", expected, output)
+	}
+}
+
+func TestGetEndpoint_None(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+	output := cli.getEndpoint(blobServiceName, "", url.Values{})
+
+	if expected := "https://foo.blob.core.windows.net/"; output != expected {
+		t.Fatalf("Wrong endpoint url. Expected: '%s', got: '%s'", expected, output)
+	}
+}
+
+func TestGetEndpoint_PathOnly(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+	output := cli.getEndpoint(blobServiceName, "path", url.Values{})
+
+	if expected := "https://foo.blob.core.windows.net/path"; output != expected {
+		t.Fatalf("Wrong endpoint url. Expected: '%s', got: '%s'", expected, output)
+	}
+}
+
+func TestGetEndpoint_ParamsOnly(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+	params := url.Values{}
+	params.Set("a", "b")
+	params.Set("c", "d")
+	output := cli.getEndpoint(blobServiceName, "", params)
+
+	if expected := "https://foo.blob.core.windows.net/?a=b&c=d"; output != expected {
+		t.Fatalf("Wrong endpoint url. Expected: '%s', got: '%s'", expected, output)
+	}
+}
+
+func TestGetEndpoint_Mixed(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+	params := url.Values{}
+	params.Set("a", "b")
+	params.Set("c", "d")
+	output := cli.getEndpoint(blobServiceName, "path", params)
+
+	if expected := "https://foo.blob.core.windows.net/path?a=b&c=d"; output != expected {
+		t.Fatalf("Wrong endpoint url. Expected: '%s', got: '%s'", expected, output)
+	}
+}
+
+func Test_getStandardHeaders(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	headers := cli.getStandardHeaders()
+	if len(headers) != 2 {
+		t.Fatal("Wrong standard header count")
+	}
+	if v, ok := headers["x-ms-version"]; !ok || v != cli.apiVersion {
+		t.Fatal("Wrong version header")
+	}
+	if _, ok := headers["x-ms-date"]; !ok {
+		t.Fatal("Missing date header")
+	}
+}
+
+func Test_buildCanonicalizedResource(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type test struct{ url, expected string }
+	tests := []test{
+		{"https://foo.blob.core.windows.net/path?a=b&c=d", "/foo/path\na:b\nc:d"},
+		{"https://foo.blob.core.windows.net/?comp=list", "/foo/\ncomp:list"},
+		{"https://foo.blob.core.windows.net/cnt/blob", "/foo/cnt/blob"},
+	}
+
+	for _, i := range tests {
+		if out, err := cli.buildCanonicalizedResource(i.url); err != nil {
+			t.Fatal(err)
+		} else if out != i.expected {
+			t.Fatalf("Wrong canonicalized resource. Expected:\n'%s', Got:\n'%s'", i.expected, out)
+		}
+	}
+}
+
+func Test_buildCanonicalizedHeader(t *testing.T) {
+	cli, err := NewBasicClient("foo", "YmFy")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type test struct {
+		headers  map[string]string
+		expected string
+	}
+	tests := []test{
+		{map[string]string{}, ""},
+		{map[string]string{"x-ms-foo": "bar"}, "x-ms-foo:bar"},
+		{map[string]string{"foo:": "bar"}, ""},
+		{map[string]string{"foo:": "bar", "x-ms-foo": "bar"}, "x-ms-foo:bar"},
+		{map[string]string{
+			"x-ms-version":   "9999-99-99",
+			"x-ms-blob-type": "BlockBlob"}, "x-ms-blob-type:BlockBlob\nx-ms-version:9999-99-99"}}
+
+	for _, i := range tests {
+		if out := cli.buildCanonicalizedHeader(i.headers); out != i.expected {
+			t.Fatalf("Wrong canonicalized resource. Expected:\n'%s', Got:\n'%s'", i.expected, out)
+		}
+	}
+}
+
+func TestReturnsStorageServiceError(t *testing.T) {
+	cli, err := getBlobClient()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// attempt to delete a nonexisting container
+	_, err = cli.deleteContainer(randContainer())
+	if err == nil {
+		t.Fatal("Service has not returned an error")
+	}
+
+	if v, ok := err.(StorageServiceError); !ok {
+		t.Fatal("Cannot assert to specific error")
+	} else if v.StatusCode != 404 {
+		t.Fatalf("Expected status:%d, got: %d", 404, v.StatusCode)
+	} else if v.Code != "ContainerNotFound" {
+		t.Fatalf("Expected code: %s, got: %s", "ContainerNotFound", v.Code)
+	} else if v.RequestId == "" {
+		t.Fatalf("RequestId does not exist")
+	}
+}
+
+func Test_createAuthorizationHeader(t *testing.T) {
+	key := base64.StdEncoding.EncodeToString([]byte("bar"))
+	cli, err := NewBasicClient("foo", key)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	canonicalizedString := `foobarzoo`
+	expected := `SharedKey foo:h5U0ATVX6SpbFX1H6GNuxIMeXXCILLoIvhflPtuQZ30=`
+
+	if out := cli.createAuthorizationHeader(canonicalizedString); out != expected {
+		t.Fatalf("Wrong authorization header. Expected: '%s', Got:'%s'", expected, out)
+	}
+}

Godeps/_workspace/src/github.com/MSOpenTech/azure-sdk-for-go/clients/storage/util.go

@@ -0,0 +1,63 @@
+package storage
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+func (c StorageClient) computeHmac256(message string) string {
+	h := hmac.New(sha256.New, c.accountKey)
+	h.Write([]byte(message))
+	return base64.StdEncoding.EncodeToString(h.Sum(nil))
+}
+
+func currentTimeRfc1123Formatted() string {
+	return timeRfc1123Formatted(time.Now().UTC())
+}
+
+func timeRfc1123Formatted(t time.Time) string {
+	return t.Format(http.TimeFormat)
+}
+
+func mergeParams(v1, v2 url.Values) url.Values {
+	out := url.Values{}
+	for k, v := range v1 {
+		out[k] = v
+	}
+	for k, v := range v2 {
+		vals, ok := out[k]
+		if ok {
+			vals = append(vals, v...)
+			out[k] = vals
+		} else {
+			out[k] = v
+		}
+	}
+	return out
+}
+
+func prepareBlockListRequest(blocks []Block) string {
+	s := `<?xml version="1.0" encoding="utf-8"?><BlockList>`
+	for _, v := range blocks {
+		s += fmt.Sprintf("<%s>%s</%s>", v.Status, v.Id, v.Status)
+	}
+	s += `</BlockList>`
+	return s
+}
+
+func xmlUnmarshal(body io.ReadCloser, v interface{}) error {
+	data, err := ioutil.ReadAll(body)
+	if err != nil {
+		return err
+	}
+	defer body.Close()
+	return xml.Unmarshal(data, v)
+}

Godeps/_workspace/src/github.com/MSOpenTech/azure-sdk-for-go/clients/storage/util_test.go

@@ -0,0 +1,80 @@
+package storage
+
+import (
+	"io/ioutil"
+	"net/url"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+func Test_timeRfc1123Formatted(t *testing.T) {
+	now := time.Now().UTC()
+
+	expectedLayout := "Mon, 02 Jan 2006 15:04:05 GMT"
+	expected := now.Format(expectedLayout)
+
+	if output := timeRfc1123Formatted(now); output != expected {
+		t.Errorf("Expected: %s, got: %s", expected, output)
+	}
+}
+
+func Test_mergeParams(t *testing.T) {
+	v1 := url.Values{
+		"k1": {"v1"},
+		"k2": {"v2"}}
+	v2 := url.Values{
+		"k1": {"v11"},
+		"k3": {"v3"}}
+
+	out := mergeParams(v1, v2)
+	if v := out.Get("k1"); v != "v1" {
+		t.Errorf("Wrong value for k1: %s", v)
+	}
+
+	if v := out.Get("k2"); v != "v2" {
+		t.Errorf("Wrong value for k2: %s", v)
+	}
+
+	if v := out.Get("k3"); v != "v3" {
+		t.Errorf("Wrong value for k3: %s", v)
+	}
+
+	if v := out["k1"]; !reflect.DeepEqual(v, []string{"v1", "v11"}) {
+		t.Errorf("Wrong multi-value for k1: %s", v)
+	}
+}
+
+func Test_prepareBlockListRequest(t *testing.T) {
+	empty := []Block{}
+	expected := `<?xml version="1.0" encoding="utf-8"?><BlockList></BlockList>`
+	if out := prepareBlockListRequest(empty); expected != out {
+		t.Errorf("Wrong block list. Expected: '%s', got: '%s'", expected, out)
+	}
+
+	blocks := []Block{{"foo", BlockStatusLatest}, {"bar", BlockStatusUncommitted}}
+	expected = `<?xml version="1.0" encoding="utf-8"?><BlockList><Latest>foo</Latest><Uncommitted>bar</Uncommitted></BlockList>`
+	if out := prepareBlockListRequest(blocks); expected != out {
+		t.Errorf("Wrong block list. Expected: '%s', got: '%s'", expected, out)
+	}
+}
+
+func Test_xmlUnmarshal(t *testing.T) {
+	xml := `<?xml version="1.0" encoding="utf-8"?>
+	<Blob>
+		<Name>myblob</Name>
+	</Blob>`
+
+	body := ioutil.NopCloser(strings.NewReader(xml))
+
+	var blob Blob
+	err := xmlUnmarshal(body, &blob)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if blob.Name != "myblob" {
+		t.Fatal("Got wrong value")
+	}
+}

cmd/registry-storagedriver-azure/main.go

@@ -14,7 +14,7 @@ import (
 // An out-of-process Azure Storage driver, intended to be run by ipc.NewDriverClient
 func main() {
 	parametersBytes := []byte(os.Args[1])
-	var parameters map[string]string
+	var parameters map[string]interface{}
 	err := json.Unmarshal(parametersBytes, &parameters)
 	if err != nil {
 		panic(err)

storagedriver/azure/azure.go

@@ -1,19 +1,18 @@
-// +build ignore
-
 // Package azure provides a storagedriver.StorageDriver implementation to
 // store blobs in Microsoft Azure Blob Storage Service.
 package azure
 
 import (
 	"bytes"
-	"encoding/base64"
 	"fmt"
 	"io"
 	"io/ioutil"
-	"strconv"
+	"net/http"
 	"strings"
+	"time"
 
 	"github.com/docker/distribution/storagedriver"
+	"github.com/docker/distribution/storagedriver/base"
 	"github.com/docker/distribution/storagedriver/factory"
 
 	azure "github.com/MSOpenTech/azure-sdk-for-go/clients/storage"
@@ -27,41 +26,45 @@ const (
 	paramContainer   = "container"
 )
 
-// Driver is a storagedriver.StorageDriver implementation backed by
+type driver struct {
-// Microsoft Azure Blob Storage Service.
+	client    azure.BlobStorageClient
-type Driver struct {
-	client    *azure.BlobStorageClient
 	container string
 }
 
+type baseEmbed struct{ base.Base }
+
+// Driver is a storagedriver.StorageDriver implementation backed by
+// Microsoft Azure Blob Storage Service.
+type Driver struct{ baseEmbed }
+
 func init() {
 	factory.Register(driverName, &azureDriverFactory{})
 }
 
 type azureDriverFactory struct{}
 
-func (factory *azureDriverFactory) Create(parameters map[string]string) (storagedriver.StorageDriver, error) {
+func (factory *azureDriverFactory) Create(parameters map[string]interface{}) (storagedriver.StorageDriver, error) {
 	return FromParameters(parameters)
 }
 
 // FromParameters constructs a new Driver with a given parameters map.
-func FromParameters(parameters map[string]string) (*Driver, error) {
+func FromParameters(parameters map[string]interface{}) (*Driver, error) {
 	accountName, ok := parameters[paramAccountName]
-	if !ok {
+	if !ok || fmt.Sprint(accountName) == "" {
 		return nil, fmt.Errorf("No %s parameter provided", paramAccountName)
 	}
 
 	accountKey, ok := parameters[paramAccountKey]
-	if !ok {
+	if !ok || fmt.Sprint(accountKey) == "" {
 		return nil, fmt.Errorf("No %s parameter provided", paramAccountKey)
 	}
 
 	container, ok := parameters[paramContainer]
-	if !ok {
+	if !ok || fmt.Sprint(container) == "" {
 		return nil, fmt.Errorf("No %s parameter provided", paramContainer)
 	}
 
-	return New(accountName, accountKey, container)
+	return New(fmt.Sprint(accountName), fmt.Sprint(accountKey), fmt.Sprint(container))
 }
 
 // New constructs a new Driver with the given Azure Storage Account credentials
@@ -78,15 +81,16 @@ func New(accountName, accountKey, container string) (*Driver, error) {
 		return nil, err
 	}
 
-	return &Driver{
+	d := &driver{
-		client:    blobClient,
+		client:    *blobClient,
-		container: container}, nil
+		container: container}
+	return &Driver{baseEmbed: baseEmbed{Base: base.Base{StorageDriver: d}}}, nil
 }
 
 // Implement the storagedriver.StorageDriver interface.
 
 // GetContent retrieves the content stored at "path" as a []byte.
-func (d *Driver) GetContent(path string) ([]byte, error) {
+func (d *driver) GetContent(path string) ([]byte, error) {
 	blob, err := d.client.GetBlob(d.container, path)
 	if err != nil {
 		if is404(err) {
@@ -99,26 +103,27 @@ func (d *Driver) GetContent(path string) ([]byte, error) {
 }
 
 // PutContent stores the []byte content at a location designated by "path".
-func (d *Driver) PutContent(path string, contents []byte) error {
+func (d *driver) PutContent(path string, contents []byte) error {
 	return d.client.PutBlockBlob(d.container, path, ioutil.NopCloser(bytes.NewReader(contents)))
 }
 
 // ReadStream retrieves an io.ReadCloser for the content stored at "path" with a
 // given byte offset.
-func (d *Driver) ReadStream(path string, offset int64) (io.ReadCloser, error) {
+func (d *driver) ReadStream(path string, offset int64) (io.ReadCloser, error) {
 	if ok, err := d.client.BlobExists(d.container, path); err != nil {
 		return nil, err
 	} else if !ok {
 		return nil, storagedriver.PathNotFoundError{Path: path}
 	}
 
-	size, err := d.CurrentSize(path)
+	info, err := d.client.GetBlobProperties(d.container, path)
 	if err != nil {
 		return nil, err
 	}
 
-	if offset >= int64(size) {
+	size := int64(info.ContentLength)
-		return nil, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
+	if offset >= size {
+		return ioutil.NopCloser(bytes.NewReader(nil)), nil
 	}
 
 	bytesRange := fmt.Sprintf("%v-", offset)
@@ -131,91 +136,77 @@ func (d *Driver) ReadStream(path string, offset int64) (io.ReadCloser, error) {
 
 // WriteStream stores the contents of the provided io.ReadCloser at a location
 // designated by the given path.
-func (d *Driver) WriteStream(path string, offset, size int64, reader io.ReadCloser) error {
+func (d *driver) WriteStream(path string, offset int64, reader io.Reader) (int64, error) {
-	var (
-		lastBlockNum    int
-		resumableOffset int64
-		blocks          []azure.Block
-	)
-
 	if blobExists, err := d.client.BlobExists(d.container, path); err != nil {
-		return err
+		return 0, err
-	} else if !blobExists { // new blob
+	} else if !blobExists {
-		lastBlockNum = 0
+		err := d.client.CreateBlockBlob(d.container, path)
-		resumableOffset = 0
-	} else { // append
-		if parts, err := d.client.GetBlockList(d.container, path, azure.BlockListTypeCommitted); err != nil {
-			return err
-		} else if len(parts.CommittedBlocks) == 0 {
-			lastBlockNum = 0
-			resumableOffset = 0
-		} else {
-			lastBlock := parts.CommittedBlocks[len(parts.CommittedBlocks)-1]
-			if lastBlockNum, err = blockNum(lastBlock.Name); err != nil {
-				return fmt.Errorf("Cannot parse block name as number '%s': %s", lastBlock.Name, err.Error())
-			}
-
-			var totalSize int64
-			for _, v := range parts.CommittedBlocks {
-				blocks = append(blocks, azure.Block{
-					Id:     v.Name,
-					Status: azure.BlockStatusCommitted})
-				totalSize += int64(v.Size)
-			}
-
-			// NOTE: Azure driver currently supports only append mode (resumable
-			// index is exactly where the committed blocks of the blob end).
-			// In order to support writing to offsets other than last index,
-			// adjacent blocks overlapping with the [offset:offset+size] area
-			// must be fetched, splitted and should be overwritten accordingly.
-			// As the current use of this method is append only, that implementation
-			// is omitted.
-			resumableOffset = totalSize
-		}
-	}
-
-	if offset != resumableOffset {
-		return storagedriver.InvalidOffsetError{Path: path, Offset: offset}
-	}
-
-	// Put content
-	buf := make([]byte, azure.MaxBlobBlockSize)
-	for {
-		// Read chunks of exactly size N except the last chunk to
-		// maximize block size and minimize block count.
-		n, err := io.ReadFull(reader, buf)
-		if err == io.EOF {
-			break
-		}
-
-		data := buf[:n]
-		blockID := toBlockID(lastBlockNum + 1)
-		if err = d.client.PutBlock(d.container, path, blockID, data); err != nil {
-			return err
-		}
-		blocks = append(blocks, azure.Block{
-			Id:     blockID,
-			Status: azure.BlockStatusLatest})
-		lastBlockNum++
-	}
-
-	// Commit block list
-	return d.client.PutBlockList(d.container, path, blocks)
-}
-
-// CurrentSize retrieves the curernt size in bytes of the object at the given
-// path.
-func (d *Driver) CurrentSize(path string) (uint64, error) {
-	props, err := d.client.GetBlobProperties(d.container, path)
 		if err != nil {
 			return 0, err
 		}
-	return props.ContentLength, nil
+	}
+	if offset < 0 {
+		return 0, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
+	}
+
+	bs := newAzureBlockStorage(d.client)
+	bw := newRandomBlobWriter(&bs, azure.MaxBlobBlockSize)
+	zw := newZeroFillWriter(&bw)
+	return zw.Write(d.container, path, offset, reader)
+}
+
+// Stat retrieves the FileInfo for the given path, including the current size
+// in bytes and the creation time.
+func (d *driver) Stat(path string) (storagedriver.FileInfo, error) {
+	// Check if the path is a blob
+	if ok, err := d.client.BlobExists(d.container, path); err != nil {
+		return nil, err
+	} else if ok {
+		blob, err := d.client.GetBlobProperties(d.container, path)
+		if err != nil {
+			return nil, err
+		}
+
+		mtim, err := time.Parse(http.TimeFormat, blob.LastModified)
+		if err != nil {
+			return nil, err
+		}
+
+		return storagedriver.FileInfoInternal{FileInfoFields: storagedriver.FileInfoFields{
+			Path:    path,
+			Size:    int64(blob.ContentLength),
+			ModTime: mtim,
+			IsDir:   false,
+		}}, nil
+	}
+
+	// Check if path is a virtual container
+	virtContainerPath := path
+	if !strings.HasSuffix(virtContainerPath, "/") {
+		virtContainerPath += "/"
+	}
+	blobs, err := d.client.ListBlobs(d.container, azure.ListBlobsParameters{
+		Prefix:     virtContainerPath,
+		MaxResults: 1,
+	})
+	if err != nil {
+		return nil, err
+	}
+	if len(blobs.Blobs) > 0 {
+		// path is a virtual container
+		return storagedriver.FileInfoInternal{FileInfoFields: storagedriver.FileInfoFields{
+			Path:  path,
+			IsDir: true,
+		}}, nil
+	}
+
+	// path is not a blob or virtual container
+	return nil, storagedriver.PathNotFoundError{Path: path}
 }
 
 // List returns a list of the objects that are direct descendants of the given
 // path.
-func (d *Driver) List(path string) ([]string, error) {
+func (d *driver) List(path string) ([]string, error) {
 	if path == "/" {
 		path = ""
 	}
@@ -231,7 +222,7 @@ func (d *Driver) List(path string) ([]string, error) {
 
 // Move moves an object stored at sourcePath to destPath, removing the original
 // object.
-func (d *Driver) Move(sourcePath string, destPath string) error {
+func (d *driver) Move(sourcePath string, destPath string) error {
 	sourceBlobURL := d.client.GetBlobUrl(d.container, sourcePath)
 	err := d.client.CopyBlob(d.container, destPath, sourceBlobURL)
 	if err != nil {
@@ -245,7 +236,7 @@ func (d *Driver) Move(sourcePath string, destPath string) error {
 }
 
 // Delete recursively deletes all objects stored at "path" and its subpaths.
-func (d *Driver) Delete(path string) error {
+func (d *driver) Delete(path string) error {
 	ok, err := d.client.DeleteBlobIfExists(d.container, path)
 	if err != nil {
 		return err
@@ -272,6 +263,21 @@ func (d *Driver) Delete(path string) error {
 	return nil
 }
 
+// URLFor returns a publicly accessible URL for the blob stored at given path
+// for specified duration by making use of Azure Storage Shared Access Signatures (SAS).
+// See https://msdn.microsoft.com/en-us/library/azure/ee395415.aspx for more info.
+func (d *driver) URLFor(path string, options map[string]interface{}) (string, error) {
+	expiresTime := time.Now().UTC().Add(20 * time.Minute) // default expiration
+	expires, ok := options["expiry"]
+	if ok {
+		t, ok := expires.(time.Time)
+		if ok {
+			expiresTime = t
+		}
+	}
+	return d.client.GetBlobSASURI(d.container, path, expiresTime, "r")
+}
+
 // directDescendants will find direct descendants (blobs or virtual containers)
 // of from list of blob paths and will return their full paths. Elements in blobs
 // list must be prefixed with a "/" and
@@ -306,7 +312,7 @@ func directDescendants(blobs []string, prefix string) []string {
 	return keys
 }
 
-func (d *Driver) listBlobs(container, virtPath string) ([]string, error) {
+func (d *driver) listBlobs(container, virtPath string) ([]string, error) {
 	if virtPath != "" && !strings.HasSuffix(virtPath, "/") { // containerify the path
 		virtPath += "/"
 	}
@@ -339,16 +345,3 @@ func is404(err error) bool {
 	e, ok := err.(azure.StorageServiceError)
 	return ok && e.StatusCode == 404
 }
-
-func blockNum(b64Name string) (int, error) {
-	s, err := base64.StdEncoding.DecodeString(b64Name)
-	if err != nil {
-		return 0, err
-	}
-
-	return strconv.Atoi(string(s))
-}
-
-func toBlockID(i int) string {
-	return base64.StdEncoding.EncodeToString([]byte(strconv.Itoa(i)))
-}

storagedriver/azure/azure_test.go

@@ -1,5 +1,3 @@
-// +build ignore
-
 package azure
 
 import (
@@ -59,9 +57,9 @@ func init() {
 	}
 
 	testsuites.RegisterInProcessSuite(azureDriverConstructor, skipCheck)
-	testsuites.RegisterIPCSuite(driverName, map[string]string{
+	// testsuites.RegisterIPCSuite(driverName, map[string]string{
-		paramAccountName: accountName,
+	// 	paramAccountName: accountName,
-		paramAccountKey:  accountKey,
+	// 	paramAccountKey:  accountKey,
-		paramContainer:   container,
+	// 	paramContainer:   container,
-	}, skipCheck)
+	// }, skipCheck)
 }

storagedriver/azure/blockblob.go

@@ -0,0 +1,24 @@
+package azure
+
+import (
+	"fmt"
+	"io"
+
+	azure "github.com/MSOpenTech/azure-sdk-for-go/clients/storage"
+)
+
+// azureBlockStorage is adaptor between azure.BlobStorageClient and
+// blockStorage interface.
+type azureBlockStorage struct {
+	azure.BlobStorageClient
+}
+
+func (b *azureBlockStorage) GetSectionReader(container, blob string, start, length int64) (io.ReadCloser, error) {
+	return b.BlobStorageClient.GetBlobRange(container, blob, fmt.Sprintf("%v-%v", start, start+length-1))
+}
+
+func newAzureBlockStorage(b azure.BlobStorageClient) azureBlockStorage {
+	a := azureBlockStorage{}
+	a.BlobStorageClient = b
+	return a
+}

storagedriver/azure/blockblob_test.go

@@ -0,0 +1,155 @@
+package azure
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+
+	azure "github.com/MSOpenTech/azure-sdk-for-go/clients/storage"
+)
+
+type StorageSimulator struct {
+	blobs map[string]*BlockBlob
+}
+
+type BlockBlob struct {
+	blocks    map[string]*DataBlock
+	blockList []string
+}
+
+type DataBlock struct {
+	data      []byte
+	committed bool
+}
+
+func (s *StorageSimulator) path(container, blob string) string {
+	return fmt.Sprintf("%s/%s", container, blob)
+}
+
+func (s *StorageSimulator) BlobExists(container, blob string) (bool, error) {
+	_, ok := s.blobs[s.path(container, blob)]
+	return ok, nil
+}
+
+func (s *StorageSimulator) GetBlob(container, blob string) (io.ReadCloser, error) {
+	bb, ok := s.blobs[s.path(container, blob)]
+	if !ok {
+		return nil, fmt.Errorf("blob not found")
+	}
+
+	var readers []io.Reader
+	for _, bID := range bb.blockList {
+		readers = append(readers, bytes.NewReader(bb.blocks[bID].data))
+	}
+	return ioutil.NopCloser(io.MultiReader(readers...)), nil
+}
+
+func (s *StorageSimulator) GetSectionReader(container, blob string, start, length int64) (io.ReadCloser, error) {
+	r, err := s.GetBlob(container, blob)
+	if err != nil {
+		return nil, err
+	}
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	return ioutil.NopCloser(bytes.NewReader(b[start : start+length])), nil
+}
+
+func (s *StorageSimulator) CreateBlockBlob(container, blob string) error {
+	path := s.path(container, blob)
+	bb := &BlockBlob{
+		blocks:    make(map[string]*DataBlock),
+		blockList: []string{},
+	}
+	s.blobs[path] = bb
+	return nil
+}
+
+func (s *StorageSimulator) PutBlock(container, blob, blockID string, chunk []byte) error {
+	path := s.path(container, blob)
+	bb, ok := s.blobs[path]
+	if !ok {
+		return fmt.Errorf("blob not found")
+	}
+	data := make([]byte, len(chunk))
+	copy(data, chunk)
+	bb.blocks[blockID] = &DataBlock{data: data, committed: false} // add block to blob
+	return nil
+}
+
+func (s *StorageSimulator) GetBlockList(container, blob string, blockType azure.BlockListType) (azure.BlockListResponse, error) {
+	resp := azure.BlockListResponse{}
+	bb, ok := s.blobs[s.path(container, blob)]
+	if !ok {
+		return resp, fmt.Errorf("blob not found")
+	}
+
+	// Iterate committed blocks (in order)
+	if blockType == azure.BlockListTypeAll || blockType == azure.BlockListTypeCommitted {
+		for _, blockID := range bb.blockList {
+			b := bb.blocks[blockID]
+			block := azure.BlockResponse{
+				Name: blockID,
+				Size: int64(len(b.data)),
+			}
+			resp.CommittedBlocks = append(resp.CommittedBlocks, block)
+		}
+
+	}
+
+	// Iterate uncommitted blocks (in no order)
+	if blockType == azure.BlockListTypeAll || blockType == azure.BlockListTypeCommitted {
+		for blockID, b := range bb.blocks {
+			block := azure.BlockResponse{
+				Name: blockID,
+				Size: int64(len(b.data)),
+			}
+			if !b.committed {
+				resp.UncommittedBlocks = append(resp.UncommittedBlocks, block)
+			}
+		}
+	}
+	return resp, nil
+}
+
+func (s *StorageSimulator) PutBlockList(container, blob string, blocks []azure.Block) error {
+	bb, ok := s.blobs[s.path(container, blob)]
+	if !ok {
+		return fmt.Errorf("blob not found")
+	}
+
+	var blockIDs []string
+	for _, v := range blocks {
+		bl, ok := bb.blocks[v.Id]
+		if !ok { // check if block ID exists
+			return fmt.Errorf("Block id '%s' not found", v.Id)
+		}
+		bl.committed = true
+		blockIDs = append(blockIDs, v.Id)
+	}
+
+	// Mark all other blocks uncommitted
+	for k, b := range bb.blocks {
+		inList := false
+		for _, v := range blockIDs {
+			if k == v {
+				inList = true
+				break
+			}
+		}
+		if !inList {
+			b.committed = false
+		}
+	}
+
+	bb.blockList = blockIDs
+	return nil
+}
+
+func NewStorageSimulator() StorageSimulator {
+	return StorageSimulator{
+		blobs: make(map[string]*BlockBlob),
+	}
+}

storagedriver/azure/blockid.go

@@ -0,0 +1,60 @@
+package azure
+
+import (
+	"encoding/base64"
+	"fmt"
+	"math/rand"
+	"sync"
+	"time"
+
+	azure "github.com/MSOpenTech/azure-sdk-for-go/clients/storage"
+)
+
+type blockIDGenerator struct {
+	pool map[string]bool
+	r    *rand.Rand
+	m    sync.Mutex
+}
+
+// Generate returns an unused random block id and adds the generated ID
+// to list of used IDs so that the same block name is not used again.
+func (b *blockIDGenerator) Generate() string {
+	b.m.Lock()
+	defer b.m.Unlock()
+
+	var id string
+	for {
+		id = toBlockID(int(b.r.Int()))
+		if !b.exists(id) {
+			break
+		}
+	}
+	b.pool[id] = true
+	return id
+}
+
+func (b *blockIDGenerator) exists(id string) bool {
+	_, used := b.pool[id]
+	return used
+}
+
+func (b *blockIDGenerator) Feed(blocks azure.BlockListResponse) {
+	b.m.Lock()
+	defer b.m.Unlock()
+
+	for _, bl := range append(blocks.CommittedBlocks, blocks.UncommittedBlocks...) {
+		b.pool[bl.Name] = true
+	}
+}
+
+func newBlockIDGenerator() *blockIDGenerator {
+	return &blockIDGenerator{
+		pool: make(map[string]bool),
+		r:    rand.New(rand.NewSource(time.Now().UnixNano()))}
+}
+
+// toBlockId converts given integer to base64-encoded block ID of a fixed length.
+func toBlockID(i int) string {
+	s := fmt.Sprintf("%029d", i) // add zero padding for same length-blobs
+	return base64.StdEncoding.EncodeToString([]byte(s))
+}

storagedriver/azure/blockid_test.go

@@ -0,0 +1,74 @@
+package azure
+
+import (
+	"math"
+	"testing"
+
+	azure "github.com/MSOpenTech/azure-sdk-for-go/clients/storage"
+)
+
+func Test_blockIdGenerator(t *testing.T) {
+	r := newBlockIDGenerator()
+
+	for i := 1; i <= 10; i++ {
+		if expected := i - 1; len(r.pool) != expected {
+			t.Fatalf("rand pool had wrong number of items: %d, expected:%d", len(r.pool), expected)
+		}
+		if id := r.Generate(); id == "" {
+			t.Fatal("returned empty id")
+		}
+		if expected := i; len(r.pool) != expected {
+			t.Fatalf("rand pool has wrong number of items: %d, expected:%d", len(r.pool), expected)
+		}
+	}
+}
+
+func Test_blockIdGenerator_Feed(t *testing.T) {
+	r := newBlockIDGenerator()
+	if expected := 0; len(r.pool) != expected {
+		t.Fatalf("rand pool had wrong number of items: %d, expected:%d", len(r.pool), expected)
+	}
+
+	// feed empty list
+	blocks := azure.BlockListResponse{}
+	r.Feed(blocks)
+	if expected := 0; len(r.pool) != expected {
+		t.Fatalf("rand pool had wrong number of items: %d, expected:%d", len(r.pool), expected)
+	}
+
+	// feed blocks
+	blocks = azure.BlockListResponse{
+		CommittedBlocks: []azure.BlockResponse{
+			{"1", 1},
+			{"2", 2},
+		},
+		UncommittedBlocks: []azure.BlockResponse{
+			{"3", 3},
+		}}
+	r.Feed(blocks)
+	if expected := 3; len(r.pool) != expected {
+		t.Fatalf("rand pool had wrong number of items: %d, expected:%d", len(r.pool), expected)
+	}
+
+	// feed same block IDs with committed/uncommitted place changed
+	blocks = azure.BlockListResponse{
+		CommittedBlocks: []azure.BlockResponse{
+			{"3", 3},
+		},
+		UncommittedBlocks: []azure.BlockResponse{
+			{"1", 1},
+		}}
+	r.Feed(blocks)
+	if expected := 3; len(r.pool) != expected {
+		t.Fatalf("rand pool had wrong number of items: %d, expected:%d", len(r.pool), expected)
+	}
+}
+
+func Test_toBlockId(t *testing.T) {
+	min := 0
+	max := math.MaxInt64
+
+	if len(toBlockID(min)) != len(toBlockID(max)) {
+		t.Fatalf("different-sized blockIDs are returned")
+	}
+}

storagedriver/azure/randomwriter.go

@@ -0,0 +1,208 @@
+package azure
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+
+	azure "github.com/MSOpenTech/azure-sdk-for-go/clients/storage"
+)
+
+// blockStorage is the interface required from a block storage service
+// client implementation
+type blockStorage interface {
+	CreateBlockBlob(container, blob string) error
+	GetBlob(container, blob string) (io.ReadCloser, error)
+	GetSectionReader(container, blob string, start, length int64) (io.ReadCloser, error)
+	PutBlock(container, blob, blockID string, chunk []byte) error
+	GetBlockList(container, blob string, blockType azure.BlockListType) (azure.BlockListResponse, error)
+	PutBlockList(container, blob string, blocks []azure.Block) error
+}
+
+// randomBlobWriter enables random access semantics on Azure block blobs
+// by enabling writing arbitrary length of chunks to arbitrary write offsets
+// within the blob. Normally, Azure Blob Storage does not support random
+// access semantics on block blobs; however, this writer can download, split and
+// reupload the overlapping blocks and discards those being overwritten entirely.
+type randomBlobWriter struct {
+	bs        blockStorage
+	blockSize int
+}
+
+func newRandomBlobWriter(bs blockStorage, blockSize int) randomBlobWriter {
+	return randomBlobWriter{bs: bs, blockSize: blockSize}
+}
+
+// WriteBlobAt writes the given chunk to the specified position of an existing blob.
+// The offset must be equals to size of the blob or smaller than it.
+func (r *randomBlobWriter) WriteBlobAt(container, blob string, offset int64, chunk io.Reader) (int64, error) {
+	rand := newBlockIDGenerator()
+
+	blocks, err := r.bs.GetBlockList(container, blob, azure.BlockListTypeCommitted)
+	if err != nil {
+		return 0, err
+	}
+	rand.Feed(blocks) // load existing block IDs
+
+	// Check for write offset for existing blob
+	size := getBlobSize(blocks)
+	if offset < 0 || offset > size {
+		return 0, fmt.Errorf("wrong offset for Write: %v", offset)
+	}
+
+	// Upload the new chunk as blocks
+	blockList, nn, err := r.writeChunkToBlocks(container, blob, chunk, rand)
+	if err != nil {
+		return 0, err
+	}
+
+	// For non-append operations, existing blocks may need to be splitted
+	if offset != size {
+		// Split the block on the left end (if any)
+		leftBlocks, err := r.blocksLeftSide(container, blob, offset, rand)
+		if err != nil {
+			return 0, err
+		}
+		blockList = append(leftBlocks, blockList...)
+
+		// Split the block on the right end (if any)
+		rightBlocks, err := r.blocksRightSide(container, blob, offset, nn, rand)
+		if err != nil {
+			return 0, err
+		}
+		blockList = append(blockList, rightBlocks...)
+	} else {
+		// Use existing block list
+		var existingBlocks []azure.Block
+		for _, v := range blocks.CommittedBlocks {
+			existingBlocks = append(existingBlocks, azure.Block{Id: v.Name, Status: azure.BlockStatusCommitted})
+		}
+		blockList = append(existingBlocks, blockList...)
+	}
+	// Put block list
+	return nn, r.bs.PutBlockList(container, blob, blockList)
+}
+
+func (r *randomBlobWriter) GetSize(container, blob string) (int64, error) {
+	blocks, err := r.bs.GetBlockList(container, blob, azure.BlockListTypeCommitted)
+	if err != nil {
+		return 0, err
+	}
+	return getBlobSize(blocks), nil
+}
+
+// writeChunkToBlocks writes given chunk to one or multiple blocks within specified
+// blob and returns their block representations. Those blocks are not committed, yet
+func (r *randomBlobWriter) writeChunkToBlocks(container, blob string, chunk io.Reader, rand *blockIDGenerator) ([]azure.Block, int64, error) {
+	var newBlocks []azure.Block
+	var nn int64
+
+	// Read chunks of at most size N except the last chunk to
+	// maximize block size and minimize block count.
+	buf := make([]byte, r.blockSize)
+	for {
+		n, err := io.ReadFull(chunk, buf)
+		if err == io.EOF {
+			break
+		}
+		nn += int64(n)
+		data := buf[:n]
+		blockID := rand.Generate()
+		if err := r.bs.PutBlock(container, blob, blockID, data); err != nil {
+			return newBlocks, nn, err
+		}
+		newBlocks = append(newBlocks, azure.Block{Id: blockID, Status: azure.BlockStatusUncommitted})
+	}
+	return newBlocks, nn, nil
+}
+
+// blocksLeftSide returns the blocks that are going to be at the left side of
+// the writeOffset: [0, writeOffset) by identifying blocks that will remain
+// the same and splitting blocks and reuploading them as needed.
+func (r *randomBlobWriter) blocksLeftSide(container, blob string, writeOffset int64, rand *blockIDGenerator) ([]azure.Block, error) {
+	var left []azure.Block
+	bx, err := r.bs.GetBlockList(container, blob, azure.BlockListTypeAll)
+	if err != nil {
+		return left, err
+	}
+
+	o := writeOffset
+	elapsed := int64(0)
+	for _, v := range bx.CommittedBlocks {
+		blkSize := int64(v.Size)
+		if o >= blkSize { // use existing block
+			left = append(left, azure.Block{Id: v.Name, Status: azure.BlockStatusCommitted})
+			o -= blkSize
+			elapsed += blkSize
+		} else if o > 0 { // current block needs to be splitted
+			start := elapsed
+			size := o
+			part, err := r.bs.GetSectionReader(container, blob, start, size)
+			if err != nil {
+				return left, err
+			}
+			newBlockID := rand.Generate()
+
+			data, err := ioutil.ReadAll(part)
+			if err != nil {
+				return left, err
+			}
+			if err = r.bs.PutBlock(container, blob, newBlockID, data); err != nil {
+				return left, err
+			}
+			left = append(left, azure.Block{Id: newBlockID, Status: azure.BlockStatusUncommitted})
+			break
+		}
+	}
+	return left, nil
+}
+
+// blocksRightSide returns the blocks that are going to be at the right side of
+// the written chunk: [writeOffset+size, +inf) by identifying blocks that will remain
+// the same and splitting blocks and reuploading them as needed.
+func (r *randomBlobWriter) blocksRightSide(container, blob string, writeOffset int64, chunkSize int64, rand *blockIDGenerator) ([]azure.Block, error) {
+	var right []azure.Block
+
+	bx, err := r.bs.GetBlockList(container, blob, azure.BlockListTypeAll)
+	if err != nil {
+		return nil, err
+	}
+
+	re := writeOffset + chunkSize - 1 // right end of written chunk
+	var elapsed int64
+	for _, v := range bx.CommittedBlocks {
+		var (
+			bs = elapsed                     // left end of current block
+			be = elapsed + int64(v.Size) - 1 // right end of current block
+		)
+
+		if bs > re { // take the block as is
+			right = append(right, azure.Block{Id: v.Name, Status: azure.BlockStatusCommitted})
+		} else if be > re { // current block needs to be splitted
+			part, err := r.bs.GetSectionReader(container, blob, re+1, be-(re+1)+1)
+			if err != nil {
+				return right, err
+			}
+			newBlockID := rand.Generate()
+
+			data, err := ioutil.ReadAll(part)
+			if err != nil {
+				return right, err
+			}
+			if err = r.bs.PutBlock(container, blob, newBlockID, data); err != nil {
+				return right, err
+			}
+			right = append(right, azure.Block{Id: newBlockID, Status: azure.BlockStatusUncommitted})
+		}
+		elapsed += int64(v.Size)
+	}
+	return right, nil
+}
+
+func getBlobSize(blocks azure.BlockListResponse) int64 {
+	var n int64
+	for _, v := range blocks.CommittedBlocks {
+		n += int64(v.Size)
+	}
+	return n
+}

storagedriver/azure/randomwriter_test.go

@@ -0,0 +1,339 @@
+package azure
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"math/rand"
+	"reflect"
+	"strings"
+	"testing"
+
+	azure "github.com/MSOpenTech/azure-sdk-for-go/clients/storage"
+)
+
+func TestRandomWriter_writeChunkToBlocks(t *testing.T) {
+	s := NewStorageSimulator()
+	rw := newRandomBlobWriter(&s, 3)
+	rand := newBlockIDGenerator()
+	c := []byte("AAABBBCCCD")
+
+	if err := rw.bs.CreateBlockBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	}
+	bw, nn, err := rw.writeChunkToBlocks("a", "b", bytes.NewReader(c), rand)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if expected := int64(len(c)); nn != expected {
+		t.Fatalf("wrong nn:%v, expected:%v", nn, expected)
+	}
+	if expected := 4; len(bw) != expected {
+		t.Fatal("unexpected written block count")
+	}
+
+	bx, err := s.GetBlockList("a", "b", azure.BlockListTypeAll)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if expected := 0; len(bx.CommittedBlocks) != expected {
+		t.Fatal("unexpected committed block count")
+	}
+	if expected := 4; len(bx.UncommittedBlocks) != expected {
+		t.Fatalf("unexpected uncommitted block count: %d -- %#v", len(bx.UncommittedBlocks), bx)
+	}
+
+	if err := rw.bs.PutBlockList("a", "b", bw); err != nil {
+		t.Fatal(err)
+	}
+
+	r, err := rw.bs.GetBlob("a", "b")
+	if err != nil {
+		t.Fatal(err)
+	}
+	assertBlobContents(t, r, c)
+}
+
+func TestRandomWriter_blocksLeftSide(t *testing.T) {
+	blob := "AAAAABBBBBCCC"
+	cases := []struct {
+		offset          int64
+		expectedBlob    string
+		expectedPattern []azure.BlockStatus
+	}{
+		{0, "", []azure.BlockStatus{}},                                                                                      // write to beginning, discard all
+		{13, blob, []azure.BlockStatus{azure.BlockStatusCommitted, azure.BlockStatusCommitted, azure.BlockStatusCommitted}}, // write to end, no change
+		{1, "A", []azure.BlockStatus{azure.BlockStatusUncommitted}},                                                         // write at 1
+		{5, "AAAAA", []azure.BlockStatus{azure.BlockStatusCommitted}},                                                       // write just after first block
+		{6, "AAAAAB", []azure.BlockStatus{azure.BlockStatusCommitted, azure.BlockStatusUncommitted}},                        // split the second block
+		{9, "AAAAABBBB", []azure.BlockStatus{azure.BlockStatusCommitted, azure.BlockStatusUncommitted}},                     // write just after first block
+	}
+
+	for _, c := range cases {
+		s := NewStorageSimulator()
+		rw := newRandomBlobWriter(&s, 5)
+		rand := newBlockIDGenerator()
+
+		if err := rw.bs.CreateBlockBlob("a", "b"); err != nil {
+			t.Fatal(err)
+		}
+		bw, _, err := rw.writeChunkToBlocks("a", "b", strings.NewReader(blob), rand)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := rw.bs.PutBlockList("a", "b", bw); err != nil {
+			t.Fatal(err)
+		}
+		bx, err := rw.blocksLeftSide("a", "b", c.offset, rand)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		bs := []azure.BlockStatus{}
+		for _, v := range bx {
+			bs = append(bs, v.Status)
+		}
+
+		if !reflect.DeepEqual(bs, c.expectedPattern) {
+			t.Logf("Committed blocks %v", bw)
+			t.Fatalf("For offset %v: Expected pattern: %v, Got: %v\n(Returned: %v)", c.offset, c.expectedPattern, bs, bx)
+		}
+		if rw.bs.PutBlockList("a", "b", bx); err != nil {
+			t.Fatal(err)
+		}
+		r, err := rw.bs.GetBlob("a", "b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		cout, err := ioutil.ReadAll(r)
+		if err != nil {
+			t.Fatal(err)
+		}
+		outBlob := string(cout)
+		if outBlob != c.expectedBlob {
+			t.Fatalf("wrong blob contents: %v, expected: %v", outBlob, c.expectedBlob)
+		}
+	}
+}
+
+func TestRandomWriter_blocksRightSide(t *testing.T) {
+	blob := "AAAAABBBBBCCC"
+	cases := []struct {
+		offset          int64
+		size            int64
+		expectedBlob    string
+		expectedPattern []azure.BlockStatus
+	}{
+		{0, 100, "", []azure.BlockStatus{}},                                                                                             // overwrite the entire blob
+		{0, 3, "AABBBBBCCC", []azure.BlockStatus{azure.BlockStatusUncommitted, azure.BlockStatusCommitted, azure.BlockStatusCommitted}}, // split first block
+		{4, 1, "BBBBBCCC", []azure.BlockStatus{azure.BlockStatusCommitted, azure.BlockStatusCommitted}},                                 // write to last char of first block
+		{1, 6, "BBBCCC", []azure.BlockStatus{azure.BlockStatusUncommitted, azure.BlockStatusCommitted}},                                 // overwrite splits first and second block, last block remains
+		{3, 8, "CC", []azure.BlockStatus{azure.BlockStatusUncommitted}},                                                                 // overwrite a block in middle block, split end block
+		{10, 1, "CC", []azure.BlockStatus{azure.BlockStatusUncommitted}},                                                                // overwrite first byte of rightmost block
+		{11, 2, "", []azure.BlockStatus{}},                                                                                              // overwrite the rightmost index
+		{13, 20, "", []azure.BlockStatus{}},                                                                                             // append to the end
+	}
+
+	for _, c := range cases {
+		s := NewStorageSimulator()
+		rw := newRandomBlobWriter(&s, 5)
+		rand := newBlockIDGenerator()
+
+		if err := rw.bs.CreateBlockBlob("a", "b"); err != nil {
+			t.Fatal(err)
+		}
+		bw, _, err := rw.writeChunkToBlocks("a", "b", strings.NewReader(blob), rand)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := rw.bs.PutBlockList("a", "b", bw); err != nil {
+			t.Fatal(err)
+		}
+		bx, err := rw.blocksRightSide("a", "b", c.offset, c.size, rand)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		bs := []azure.BlockStatus{}
+		for _, v := range bx {
+			bs = append(bs, v.Status)
+		}
+
+		if !reflect.DeepEqual(bs, c.expectedPattern) {
+			t.Logf("Committed blocks %v", bw)
+			t.Fatalf("For offset %v-size:%v: Expected pattern: %v, Got: %v\n(Returned: %v)", c.offset, c.size, c.expectedPattern, bs, bx)
+		}
+		if rw.bs.PutBlockList("a", "b", bx); err != nil {
+			t.Fatal(err)
+		}
+		r, err := rw.bs.GetBlob("a", "b")
+		if err != nil {
+			t.Fatal(err)
+		}
+		cout, err := ioutil.ReadAll(r)
+		if err != nil {
+			t.Fatal(err)
+		}
+		outBlob := string(cout)
+		if outBlob != c.expectedBlob {
+			t.Fatalf("For offset %v-size:%v: wrong blob contents: %v, expected: %v", c.offset, c.size, outBlob, c.expectedBlob)
+		}
+	}
+}
+
+func TestRandomWriter_Write_NewBlob(t *testing.T) {
+	var (
+		s    = NewStorageSimulator()
+		rw   = newRandomBlobWriter(&s, 1024*3) // 3 KB blocks
+		blob = randomContents(1024 * 7)        // 7 KB blob
+	)
+	if err := rw.bs.CreateBlockBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := rw.WriteBlobAt("a", "b", 10, bytes.NewReader(blob)); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if _, err := rw.WriteBlobAt("a", "b", 100000, bytes.NewReader(blob)); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if nn, err := rw.WriteBlobAt("a", "b", 0, bytes.NewReader(blob)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(blob)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := rw.bs.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, blob)
+	}
+	if bx, err := rw.bs.GetBlockList("a", "b", azure.BlockListTypeCommitted); err != nil {
+		t.Fatal(err)
+	} else if len(bx.CommittedBlocks) != 3 {
+		t.Fatalf("got wrong number of committed blocks: %v", len(bx.CommittedBlocks))
+	}
+
+	// Replace first 512 bytes
+	leftChunk := randomContents(512)
+	blob = append(leftChunk, blob[512:]...)
+	if nn, err := rw.WriteBlobAt("a", "b", 0, bytes.NewReader(leftChunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(leftChunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := rw.bs.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, blob)
+	}
+	if bx, err := rw.bs.GetBlockList("a", "b", azure.BlockListTypeCommitted); err != nil {
+		t.Fatal(err)
+	} else if expected := 4; len(bx.CommittedBlocks) != expected {
+		t.Fatalf("got wrong number of committed blocks: %v, expected: %v", len(bx.CommittedBlocks), expected)
+	}
+
+	// Replace last 512 bytes with 1024 bytes
+	rightChunk := randomContents(1024)
+	offset := int64(len(blob) - 512)
+	blob = append(blob[:offset], rightChunk...)
+	if nn, err := rw.WriteBlobAt("a", "b", offset, bytes.NewReader(rightChunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(rightChunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := rw.bs.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, blob)
+	}
+	if bx, err := rw.bs.GetBlockList("a", "b", azure.BlockListTypeCommitted); err != nil {
+		t.Fatal(err)
+	} else if expected := 5; len(bx.CommittedBlocks) != expected {
+		t.Fatalf("got wrong number of committed blocks: %v, expected: %v", len(bx.CommittedBlocks), expected)
+	}
+
+	// Replace 2K-4K (overlaps 2 blocks from L/R)
+	newChunk := randomContents(1024 * 2)
+	offset = 1024 * 2
+	blob = append(append(blob[:offset], newChunk...), blob[offset+int64(len(newChunk)):]...)
+	if nn, err := rw.WriteBlobAt("a", "b", offset, bytes.NewReader(newChunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(newChunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := rw.bs.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, blob)
+	}
+	if bx, err := rw.bs.GetBlockList("a", "b", azure.BlockListTypeCommitted); err != nil {
+		t.Fatal(err)
+	} else if expected := 6; len(bx.CommittedBlocks) != expected {
+		t.Fatalf("got wrong number of committed blocks: %v, expected: %v\n%v", len(bx.CommittedBlocks), expected, bx.CommittedBlocks)
+	}
+
+	// Replace the entire blob
+	newBlob := randomContents(1024 * 30)
+	if nn, err := rw.WriteBlobAt("a", "b", 0, bytes.NewReader(newBlob)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(newBlob)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := rw.bs.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, newBlob)
+	}
+	if bx, err := rw.bs.GetBlockList("a", "b", azure.BlockListTypeCommitted); err != nil {
+		t.Fatal(err)
+	} else if expected := 10; len(bx.CommittedBlocks) != expected {
+		t.Fatalf("got wrong number of committed blocks: %v, expected: %v\n%v", len(bx.CommittedBlocks), expected, bx.CommittedBlocks)
+	} else if expected, size := int64(1024*30), getBlobSize(bx); size != expected {
+		t.Fatalf("committed block size does not indicate blob size")
+	}
+}
+
+func Test_getBlobSize(t *testing.T) {
+	// with some committed blocks
+	if expected, size := int64(151), getBlobSize(azure.BlockListResponse{
+		CommittedBlocks: []azure.BlockResponse{
+			{"A", 100},
+			{"B", 50},
+			{"C", 1},
+		},
+		UncommittedBlocks: []azure.BlockResponse{
+			{"D", 200},
+		}}); expected != size {
+		t.Fatalf("wrong blob size: %v, expected: %v", size, expected)
+	}
+
+	// with no committed blocks
+	if expected, size := int64(0), getBlobSize(azure.BlockListResponse{
+		UncommittedBlocks: []azure.BlockResponse{
+			{"A", 100},
+			{"B", 50},
+			{"C", 1},
+			{"D", 200},
+		}}); expected != size {
+		t.Fatalf("wrong blob size: %v, expected: %v", size, expected)
+	}
+}
+
+func assertBlobContents(t *testing.T, r io.Reader, expected []byte) {
+	out, err := ioutil.ReadAll(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !reflect.DeepEqual(out, expected) {
+		t.Fatalf("wrong blob contents. size: %v, expected: %v", len(out), len(expected))
+	}
+}
+
+func randomContents(length int64) []byte {
+	b := make([]byte, length)
+	for i := range b {
+		b[i] = byte(rand.Intn(2 << 8))
+	}
+	return b
+}

storagedriver/azure/zerofillwriter.go

@@ -0,0 +1,49 @@
+package azure
+
+import (
+	"bytes"
+	"io"
+)
+
+type blockBlobWriter interface {
+	GetSize(container, blob string) (int64, error)
+	WriteBlobAt(container, blob string, offset int64, chunk io.Reader) (int64, error)
+}
+
+// zeroFillWriter enables writing to an offset outside a block blob's size
+// by offering the chunk to the underlying writer as a contiguous data with
+// the gap in between filled with NUL (zero) bytes.
+type zeroFillWriter struct {
+	blockBlobWriter
+}
+
+func newZeroFillWriter(b blockBlobWriter) zeroFillWriter {
+	w := zeroFillWriter{}
+	w.blockBlobWriter = b
+	return w
+}
+
+// Write writes the given chunk to the specified existing blob even though
+// offset is out of blob's size. The gaps are filled with zeros. Returned
+// written number count does not include zeros written.
+func (z *zeroFillWriter) Write(container, blob string, offset int64, chunk io.Reader) (int64, error) {
+	size, err := z.blockBlobWriter.GetSize(container, blob)
+	if err != nil {
+		return 0, err
+	}
+
+	var reader io.Reader
+	var zeroPadding int64
+	if offset <= size {
+		reader = chunk
+	} else {
+		zeroPadding = offset - size
+		offset = size // adjust offset to be the append index
+		zeros := bytes.NewReader(make([]byte, zeroPadding))
+		reader = io.MultiReader(zeros, chunk)
+	}
+
+	nn, err := z.blockBlobWriter.WriteBlobAt(container, blob, offset, reader)
+	nn -= zeroPadding
+	return nn, err
+}

storagedriver/azure/zerofillwriter_test.go

@@ -0,0 +1,126 @@
+package azure
+
+import (
+	"bytes"
+	"testing"
+)
+
+func Test_zeroFillWrite_AppendNoGap(t *testing.T) {
+	s := NewStorageSimulator()
+	bw := newRandomBlobWriter(&s, 1024*1)
+	zw := newZeroFillWriter(&bw)
+	if err := s.CreateBlockBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	}
+
+	firstChunk := randomContents(1024*3 + 512)
+	if nn, err := zw.Write("a", "b", 0, bytes.NewReader(firstChunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(firstChunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := s.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, firstChunk)
+	}
+
+	secondChunk := randomContents(256)
+	if nn, err := zw.Write("a", "b", int64(len(firstChunk)), bytes.NewReader(secondChunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(secondChunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := s.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, append(firstChunk, secondChunk...))
+	}
+
+}
+
+func Test_zeroFillWrite_StartWithGap(t *testing.T) {
+	s := NewStorageSimulator()
+	bw := newRandomBlobWriter(&s, 1024*2)
+	zw := newZeroFillWriter(&bw)
+	if err := s.CreateBlockBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	}
+
+	chunk := randomContents(1024 * 5)
+	padding := int64(1024*2 + 256)
+	if nn, err := zw.Write("a", "b", padding, bytes.NewReader(chunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(chunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := s.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, append(make([]byte, padding), chunk...))
+	}
+}
+
+func Test_zeroFillWrite_AppendWithGap(t *testing.T) {
+	s := NewStorageSimulator()
+	bw := newRandomBlobWriter(&s, 1024*2)
+	zw := newZeroFillWriter(&bw)
+	if err := s.CreateBlockBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	}
+
+	firstChunk := randomContents(1024*3 + 512)
+	if _, err := zw.Write("a", "b", 0, bytes.NewReader(firstChunk)); err != nil {
+		t.Fatal(err)
+	}
+	if out, err := s.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, firstChunk)
+	}
+
+	secondChunk := randomContents(256)
+	padding := int64(1024 * 4)
+	if nn, err := zw.Write("a", "b", int64(len(firstChunk))+padding, bytes.NewReader(secondChunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(secondChunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := s.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, append(firstChunk, append(make([]byte, padding), secondChunk...)...))
+	}
+}
+
+func Test_zeroFillWrite_LiesWithinSize(t *testing.T) {
+	s := NewStorageSimulator()
+	bw := newRandomBlobWriter(&s, 1024*2)
+	zw := newZeroFillWriter(&bw)
+	if err := s.CreateBlockBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	}
+
+	firstChunk := randomContents(1024 * 3)
+	if _, err := zw.Write("a", "b", 0, bytes.NewReader(firstChunk)); err != nil {
+		t.Fatal(err)
+	}
+	if out, err := s.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, firstChunk)
+	}
+
+	// in this case, zerofill won't be used
+	secondChunk := randomContents(256)
+	if nn, err := zw.Write("a", "b", 0, bytes.NewReader(secondChunk)); err != nil {
+		t.Fatal(err)
+	} else if expected := int64(len(secondChunk)); expected != nn {
+		t.Fatalf("wrong written bytes count: %v, expected: %v", nn, expected)
+	}
+	if out, err := s.GetBlob("a", "b"); err != nil {
+		t.Fatal(err)
+	} else {
+		assertBlobContents(t, out, append(secondChunk, firstChunk[len(secondChunk):]...))
+	}
+}