4 files changed, 137 insertions, 1 deletions
diff --git a/go/operation/chunked_file.go b/go/operation/chunked_file.go
new file mode 100644
index 000000000..a581af574
--- /dev/null
+++ b/go/operation/chunked_file.go
@@ -0,0 +1,126 @@
+package operation
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"sort"
+
+	"github.com/chrislusf/seaweedfs/go/util"
+)
+
+var ErrOutOfRange = errors.New("Out of Range")
+
+type ChunkInfo struct {
+	Fid    string `json:"fid,omitempty"`
+	Offset uint64 `json:"offset,omitempty"`
+	Size   uint32 `json:"size,omitempty"`
+}
+
+type ChunkList []*ChunkInfo
+
+type ChunkedFile struct {
+	Name   string    `json:"name,omitempty"`
+	Mime   string    `json:"mime,omitempty"`
+	Size   uint64    `json:"size,omitempty"`
+	Chunks ChunkList `json:"chunks,omitempty"`
+
+	master string `json:"-"`
+}
+
+func (s ChunkList) Len() int           { return len(s) }
+func (s ChunkList) Less(i, j int) bool { return s[i].Offset < s[j].Offset }
+func (s ChunkList) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+func NewChunkedNeedle(buffer []byte, master string) (*ChunkedFile, error) {
+	c := ChunkedFile{}
+
+	if e := json.Unmarshal(buffer, c); e != nil {
+		return nil, e
+	}
+	sort.Sort(c.Chunks)
+	c.master = master
+	return &c, nil
+}
+
+func (c *ChunkedFile) Marshal() ([]byte, error) {
+	return json.Marshal(c)
+}
+
+func copyChunk(fileUrl string, w io.Writer, startOffset, size int64) (written int64, e error) {
+	req, err := http.NewRequest("GET", fileUrl, nil)
+	if err != nil {
+		return written, err
+	}
+	if startOffset > 0 {
+		req.Header.Set("Range", fmt.Sprintf("bytes=%d-", startOffset))
+	}
+
+	resp, err := util.Do(req)
+	if err != nil {
+		return written, err
+	}
+	defer resp.Close()
+	if startOffset > 0 && resp.StatusCode != 206 {
+		return written, fmt.Errorf("Cannot Read Needle Position: %d [%s]", startOffset, fileUrl)
+	}
+
+	if size > 0 {
+		return io.CopyN(w, resp, size)
+	} else {
+		return io.Copy(w, resp)
+	}
+}
+
+func (c *ChunkedFile) WriteBuffer(w io.Writer, offset, size int64) (written int64, e error) {
+	if offset >= c.Size || offset+size > c.Size {
+		return written, ErrOutOfRange
+	}
+	chunkIndex := -1
+	chunkStartOffset := 0
+	for i, ci := range c.Chunks {
+		if offset >= ci.Offset && offset < ci.Offset+ci.Size {
+			chunkIndex = i
+			chunkStartOffset = offset - ci.Offset
+			break
+		}
+	}
+	if chunkIndex < 0 {
+		return written, ErrOutOfRange
+	}
+	for ; chunkIndex < c.Chunks.Len(); chunkIndex++ {
+		ci := c.Chunks[chunkIndex]
+		fileUrl, lookupError := LookupFileId(c.master, ci.Fid)
+		if lookupError != nil {
+			return written, lookupError
+		}
+		rsize := 0
+		if size > 0 {
+			rsize = size - written
+		}
+		if n, e := copyChunk(fileUrl, w, chunkStartOffset, rsize); e != nil {
+			return written, e
+		} else {
+			written += n
+		}
+
+		if size > 0 && written >= size {
+			break
+		}
+		chunkStartOffset = 0
+	}
+
+	return written, nil
+}
+
+func (c *ChunkedFile) DeleteHelper() error {
+	//TODO Delete all chunks
+	return nil
+}
+
+func (c *ChunkedFile) StoredHelper() error {
+	//TODO
+	return nil
+}
diff --git a/go/storage/needle_read_write.go b/go/storage/needle_read_write.go
index eb2d8d459..2a5bd89ea 100644
--- a/go/storage/needle_read_write.go
+++ b/go/storage/needle_read_write.go
@@ -16,6 +16,7 @@ const (
 	FlagHasMime             = 0x04
 	FlagHasLastModifiedDate = 0x08
 	FlagHasTtl              = 0x10
+	FlagChunkList           = 0x80
 	LastModifiedBytesLength = 5
 	TtlBytesLength          = 2
 )
@@ -280,3 +281,11 @@ func (n *Needle) HasTtl() bool {
 func (n *Needle) SetHasTtl() {
 	n.Flags = n.Flags | FlagHasTtl
 }
+
+func (n *Needle) IsChunkList() bool {
+	return n.Flags&FlagChunkList > 0
+}
+
+func (n *Needle) SetChunkList() {
+	n.Flags = n.Flags | FlagChunkList
+}
diff --git a/go/topology/volume_location_list.go b/go/topology/volume_location_list.go
index 0f892c010..d5eaf5e92 100644
--- a/go/topology/volume_location_list.go
+++ b/go/topology/volume_location_list.go
@@ -17,6 +17,7 @@ func (dnll *VolumeLocationList) String() string {
 }
 
 func (dnll *VolumeLocationList) Head() *DataNode {
+	//mark first node as master volume
 	return dnll.list[0]
 }
 
diff --git a/go/weed/weed_server/volume_server_handlers_read.go b/go/weed/weed_server/volume_server_handlers_read.go
index d569f5510..9e252d205 100644
--- a/go/weed/weed_server/volume_server_handlers_read.go
+++ b/go/weed/weed_server/volume_server_handlers_read.go
@@ -180,7 +180,7 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 		}
 		return
 	}
-	// process mulitple ranges
+	// process multiple ranges
 	for _, ra := range ranges {
 		if ra.start > size {
 			http.Error(w, "Out of Range", http.StatusRequestedRangeNotSatisfiable)