2 files changed, 23 insertions, 0 deletions
diff --git a/src/strings/reader.go b/src/strings/reader.go
index 248e55245c..737873c099 100644
--- a/src/strings/reader.go
+++ b/src/strings/reader.go
@@ -145,6 +145,9 @@ func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
 	return
 }
 
+// Reset resets the Reader to be reading from s.
+func (r *Reader) Reset(s string) { *r = Reader{s, 0, -1} }
+
 // NewReader returns a new Reader reading from s.
 // It is similar to bytes.NewBufferString but more efficient and read-only.
 func NewReader(s string) *Reader { return &Reader{s, 0, -1} }
diff --git a/src/strings/reader_test.go b/src/strings/reader_test.go
index 5003a37be4..7bca2e89a1 100644
--- a/src/strings/reader_test.go
+++ b/src/strings/reader_test.go
@@ -170,3 +170,23 @@ func TestReaderLenSize(t *testing.T) {
 		t.Errorf("Size = %d; want 3", r.Size())
 	}
 }
+
+func TestReaderReset(t *testing.T) {
+	r := strings.NewReader("世界")
+	if _, _, err := r.ReadRune(); err != nil {
+		t.Errorf("ReadRune: unexpected error: %v", err)
+	}
+
+	const want = "abcdef"
+	r.Reset(want)
+	if err := r.UnreadRune(); err == nil {
+		t.Errorf("UnreadRune: expected error, got nil")
+	}
+	buf, err := ioutil.ReadAll(r)
+	if err != nil {
+		t.Errorf("ReadAll: unexpected error: %v", err)
+	}
+	if got := string(buf); got != want {
+		t.Errorf("ReadAll: got %q, want %q", got, want)
+	}
+}