filer: add back image resizing capability

weed/filer2/stream.go

@@ -1,7 +1,10 @@
 package filer2
 
 import (
+	"bytes"
+	"fmt"
 	"io"
+	"math"
 
 	"github.com/chrislusf/seaweedfs/weed/glog"
 	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
@@ -40,3 +43,58 @@ func StreamContent(masterClient *wdclient.MasterClient, w io.Writer, chunks []*f
 	return nil
 
 }
+
+type ChunkStreamReader struct {
+	masterClient *wdclient.MasterClient
+	chunkViews   []*ChunkView
+	logicOffset  int64
+	buffer       bytes.Buffer
+	bufferOffset int64
+	chunkIndex   int
+}
+
+var _ = io.ReadSeeker(&ChunkStreamReader{})
+
+func NewChunkStreamReader(masterClient *wdclient.MasterClient, chunks []*filer_pb.FileChunk) *ChunkStreamReader {
+
+	chunkViews := ViewFromChunks(chunks, 0, math.MaxInt32)
+
+	return &ChunkStreamReader{
+		masterClient: masterClient,
+		chunkViews:   chunkViews,
+		bufferOffset: -1,
+	}
+}
+
+func (c *ChunkStreamReader) Read(p []byte) (n int, err error) {
+	if c.buffer.Len() == 0 {
+		if c.chunkIndex >= len(c.chunkViews) {
+			return 0, io.EOF
+		}
+		chunkView := c.chunkViews[c.chunkIndex]
+		c.fetchChunkToBuffer(chunkView)
+		c.chunkIndex++
+	}
+	return c.buffer.Read(p)
+}
+
+func (c *ChunkStreamReader) Seek(offset int64, whence int) (int64, error) {
+	return 0, fmt.Errorf("ChunkStreamReader: seek not supported")
+}
+
+func (c *ChunkStreamReader) fetchChunkToBuffer(chunkView *ChunkView) error {
+	urlString, err := c.masterClient.LookupFileId(chunkView.FileId)
+	if err != nil {
+		glog.V(1).Infof("operation LookupFileId %s failed, err: %v", chunkView.FileId, err)
+		return err
+	}
+	c.buffer.Reset()
+	err = util.ReadUrlAsStream(urlString, chunkView.CipherKey, chunkView.isGzipped, chunkView.IsFullChunk, chunkView.Offset, int(chunkView.Size), func(data []byte) {
+		c.buffer.Write(data)
+	})
+	if err != nil {
+		glog.V(1).Infof("read %s failed, err: %v", chunkView.FileId, err)
+		return err
+	}
+	return nil
+}