1 files changed, 20 insertions, 1 deletions
diff --git a/libgo/go/strings/reader.go b/libgo/go/strings/reader.go
index 8569805..98325ce 100644
--- a/libgo/go/strings/reader.go
+++ b/libgo/go/strings/reader.go
@@ -10,7 +10,7 @@ import (
 	"unicode/utf8"
 )
 
-// A Reader implements the io.Reader, io.ReaderAt, io.Seeker,
+// A Reader implements the io.Reader, io.ReaderAt, io.Seeker, io.WriterTo,
 // io.ByteScanner, and io.RuneScanner interfaces by reading
 // from a string.
 type Reader struct {
@@ -120,6 +120,25 @@ func (r *Reader) Seek(offset int64, whence int) (int64, error) {
 	return abs, nil
 }
 
+// WriteTo implements the io.WriterTo interface.
+func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
+	r.prevRune = -1
+	if r.i >= len(r.s) {
+		return 0, io.EOF
+	}
+	s := r.s[r.i:]
+	m, err := io.WriteString(w, s)
+	if m > len(s) {
+		panic("strings.Reader.WriteTo: invalid WriteString count")
+	}
+	r.i += m
+	n = int64(m)
+	if m != len(s) && err == nil {
+		err = io.ErrShortWrite
+	}
+	return
+}
+
 // 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} }