mount: shortcut when there is only one chunk

weed/util/bytes.go

@@ -1,6 +1,7 @@
 package util
 
 import (
+	"bytes"
 	"crypto/md5"
 	"crypto/rand"
 	"encoding/base64"
@@ -148,3 +149,15 @@ func RandomBytes(byteCount int) []byte {
 	rand.Read(buf)
 	return buf
 }
+
+type BytesReader struct {
+	Bytes []byte
+	*bytes.Reader
+}
+
+func NewBytesReader(b []byte) *BytesReader {
+	return &BytesReader{
+		Bytes:  b,
+		Reader: bytes.NewReader(b),
+	}
+}