Introduce resetTails

multireader.go

@@ -130,6 +130,17 @@ func (mr *multiReader) Seek(offset int64, whence int) (int64, error) {
 	return 0, errors.New("invalid whence")
 }
 
+func (mr *multiReader) resetTails() error {
+	for i := mr.off + 1; i < len(mr.rs); i++ {
+		r := mr.rs[i]
+		if _, err := r.Seek(0, io.SeekStart); err != nil {
+			return err
+		}
+		r.off = 0
+	}
+	return nil
+}
+
 func (mr *multiReader) seekStart(offset int64, start int) (int64, error) {
 	off := int64(0)
 	for i := 0; i < start; i++ {
@@ -156,6 +167,9 @@ func (mr *multiReader) seekStart(offset int64, start int) (int64, error) {
 	if err != nil {
 		return 0, err
 	}
+	if err := mr.resetTails(); err != nil {
+		return 0, err
+	}
 	return off, nil
 }
 
@@ -187,6 +201,9 @@ func (mr *multiReader) seekCurrent(offset int64) (int64, error) {
 		}
 		return mr.seekEnd(diffset, mr.off-1)
 	}
+	if err := mr.resetTails(); err != nil {
+		return 0, err
+	}
 	return off + n, nil
 }
 

multireader_test.go

@@ -130,6 +130,33 @@ func TestMultiSeek(t *testing.T) {
 			whence: io.SeekStart,
 			n:      int64(4),
 			after:  "ef",
+		}, {
+			reader: func() io.ReadSeekCloser {
+				r := testMultiReaderStrings(t, "abc", "def")
+				ioutil.ReadAll(r)
+				return r
+			},
+			offset: int64(0),
+			whence: io.SeekStart,
+			n:      int64(0),
+			after:  "abcdef",
+		}, {
+			reader: func() io.ReadSeekCloser {
+				r0 := NopReadSeekCloser(strings.NewReader("abc"))
+				r1 := strings.NewReader("def")
+				d1 := Delegate(r1)
+				r, err := MultiReadSeekCloser(r0, d1)
+				if err != nil {
+					t.Fatal(err)
+				}
+				d1.SeekFunc = func(offset int64, whence int) (int64, error) {
+					return 0, errors.New("failed to reset tails")
+				}
+				return r
+			},
+			offset: int64(0),
+			whence: io.SeekStart,
+			errstr: "failed to reset tails",
 		}, {
 			reader: func() io.ReadSeekCloser {
 				// NOTE: Check single reader.
@@ -204,6 +231,23 @@ func TestMultiSeek(t *testing.T) {
 			whence: io.SeekCurrent,
 			n:      int64(0),
 			after:  "abcdefghi",
+		}, {
+			reader: func() io.ReadSeekCloser {
+				r0 := NopReadSeekCloser(strings.NewReader("abc"))
+				r1 := strings.NewReader("def")
+				d1 := Delegate(r1)
+				r, err := MultiReadSeekCloser(r0, d1)
+				if err != nil {
+					t.Fatal(err)
+				}
+				d1.SeekFunc = func(offset int64, whence int) (int64, error) {
+					return 0, errors.New("failed to reset tails")
+				}
+				return r
+			},
+			offset: int64(0),
+			whence: io.SeekCurrent,
+			errstr: "failed to reset tails",
 		}, {
 			reader: func() io.ReadSeekCloser {
 				// NOTE: Check single reader.