bufio: WriteRune

also fix a printing error in the test for bytes.Buffer

R=golang-dev
CC=golang-dev
https://golang.org/cl/240042

src/pkg/bufio/bufio.go

@@ -437,6 +437,35 @@ func (b *Writer) WriteByte(c byte) os.Error {
 	return nil
 }
 
+// WriteRune writes a single Unicode code point, returning
+// the number of bytes written and any error.
+func (b *Writer) WriteRune(rune int) (size int, err os.Error) {
+	if rune < utf8.RuneSelf {
+		err = b.WriteByte(byte(rune))
+		if err != nil {
+			return 0, err
+		}
+		return 1, nil
+	}
+	if b.err != nil {
+		return 0, b.err
+	}
+	n := b.Available()
+	if n < utf8.UTFMax {
+		if b.Flush(); b.err != nil {
+			return 0, b.err
+		}
+		n = b.Available()
+		if n < utf8.UTFMax {
+			// Can only happen if buffer is silly small.
+			return b.WriteString(string(rune))
+		}
+	}
+	size = utf8.EncodeRune(rune, b.buf[b.n:])
+	b.n += size
+	return size, nil
+}
+
 // WriteString writes a string.
 // It returns the number of bytes written.
 // If the count is less than len(s), it also returns an error explaining

src/pkg/bufio/bufio_test.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"testing"
 	"testing/iotest"
+	"utf8"
 )
 
 // Reads from a reader and rot13s the result.
@@ -225,6 +226,35 @@ func TestReadRune(t *testing.T) {
 	}
 }
 
+func TestReadWriteRune(t *testing.T) {
+	const NRune = 1000
+	byteBuf := new(bytes.Buffer)
+	w := NewWriter(byteBuf)
+	// Write the runes out using WriteRune
+	buf := make([]byte, utf8.UTFMax)
+	for rune := 0; rune < NRune; rune++ {
+		size := utf8.EncodeRune(rune, buf)
+		nbytes, err := w.WriteRune(rune)
+		if err != nil {
+			t.Fatalf("WriteRune(0x%x) error: %s", rune, err)
+		}
+		if nbytes != size {
+			t.Fatalf("WriteRune(0x%x) expected %d, got %d", rune, size, nbytes)
+		}
+	}
+	w.Flush()
+
+	r := NewReader(byteBuf)
+	// Read them back with ReadRune
+	for rune := 0; rune < NRune; rune++ {
+		size := utf8.EncodeRune(rune, buf)
+		nr, nbytes, err := r.ReadRune()
+		if nr != rune || nbytes != size || err != nil {
+			t.Fatalf("ReadRune(0x%x) got 0x%x,%d not 0x%x,%d (err=%s)", r, nr, nbytes, r, size, err)
+		}
+	}
+}
+
 func TestWriter(t *testing.T) {
 	var data [8192]byte
 

src/pkg/bytes/buffer_test.go

@@ -277,7 +277,7 @@ func TestRuneIO(t *testing.T) {
 			t.Fatalf("WriteRune(0x%x) error: %s", r, err)
 		}
 		if nbytes != size {
-			t.Fatalf("WriteRune(0x%x) expected %d, got %d", size, nbytes)
+			t.Fatalf("WriteRune(0x%x) expected %d, got %d", r, size, nbytes)
 		}
 		n += size
 	}