untested Range support

blobserver/go/get.go

@@ -29,8 +29,34 @@ func handleGet(conn *http.Conn, req *http.Request) {
 		serverError(conn, err)
 		return
 	}
+
+	reqRange := getRequestedRange(req)
+	if reqRange.SkipBytes != 0 {
+		_, err = file.Seek(reqRange.SkipBytes, 0)
+		if err != nil {
+			serverError(conn, err)
+			return
+		}
+	}
+
+	var input io.Reader = file
+	if reqRange.LimitBytes != -1 {
+		input = io.LimitReader(file, reqRange.LimitBytes)
+	}
+
 	conn.SetHeader("Content-Type", "application/octet-stream")
-	bytesCopied, err := io.Copy(conn, file)
+	if !reqRange.IsWholeFile() {
+		remainBytes := stat.Size - reqRange.SkipBytes
+		if reqRange.LimitBytes != -1 &&
+			reqRange.LimitBytes < remainBytes {
+			remainBytes = reqRange.LimitBytes
+		}
+		conn.SetHeader("Content-Range",
+			fmt.Sprintf("%d-%d/%d", reqRange.SkipBytes,
+			reqRange.SkipBytes + remainBytes,
+			stat.Size))
+	}
+	bytesCopied, err := io.Copy(conn, input)
 
 	// If there's an error at this point, it's too late to tell the client,
 	// as they've already been receiving bytes.  But they should be smart enough

blobserver/go/range.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"http"
+	"regexp"
+	"strconv"
+)
+
+// Default is {0, -1} to read all of a file.
+type requestedRange struct {
+	SkipBytes int64
+	LimitBytes int64  // or -1 to read all
+}
+
+func (rr *requestedRange) IsWholeFile() bool {
+	return rr.SkipBytes == 0 && rr.LimitBytes == -1;
+}
+
+var wholeRange = &requestedRange{0, -1}
+
+var rangePattern = regexp.MustCompile(`bytes=([0-9]+)-([0-9]*)`)
+
+func getRequestedRange(req *http.Request) *requestedRange {
+	rrange, ok := req.Header["Range"]
+	if !ok {
+		return wholeRange
+	}
+	return getRequestedRangeFromString(rrange)
+}
+
+func getRequestedRangeFromString(rrange string) *requestedRange {
+	matches := rangePattern.MatchStrings(rrange)
+	if len(matches) == 0 {
+		return wholeRange;
+	}
+	limitBytes := int64(-1)
+	if len(matches[2]) > 0 {
+		limitBytes, _ = strconv.Atoi64(matches[2])
+	}
+	skipBytes, _ := strconv.Atoi64(matches[1])
+	limitBytes -= skipBytes
+	return &requestedRange{skipBytes, limitBytes}
+}

blobserver/go/range_test.go

@@ -0,0 +1,7 @@
+package main
+
+import "testing"
+
+func testRange(t *t.Testing) {
+	
+}