1 files changed, 108 insertions, 0 deletions
diff --git a/modules/mahonia/writer.go b/modules/mahonia/writer.go
new file mode 100644
index 00000000..bdeb519c
--- /dev/null
+++ b/modules/mahonia/writer.go
@@ -0,0 +1,108 @@
+package mahonia
+
+import (
+	"io"
+	"unicode/utf8"
+)
+
+// Writer implements character-set encoding for an io.Writer object.
+type Writer struct {
+	wr     io.Writer
+	encode Encoder
+	inbuf  []byte
+	outbuf []byte
+}
+
+// NewWriter creates a new Writer that uses the receiver to encode text.
+func (e Encoder) NewWriter(wr io.Writer) *Writer {
+	w := new(Writer)
+	w.wr = wr
+	w.encode = e
+	return w
+}
+
+// Write encodes and writes the data from p.
+func (w *Writer) Write(p []byte) (n int, err error) {
+	n = len(p)
+
+	if len(w.inbuf) > 0 {
+		w.inbuf = append(w.inbuf, p...)
+		p = w.inbuf
+	}
+
+	if len(w.outbuf) < len(p) {
+		w.outbuf = make([]byte, len(p)+10)
+	}
+
+	outpos := 0
+
+	for len(p) > 0 {
+		rune, size := utf8.DecodeRune(p)
+		if rune == 0xfffd && !utf8.FullRune(p) {
+			break
+		}
+
+		p = p[size:]
+
+	retry:
+		size, status := w.encode(w.outbuf[outpos:], rune)
+
+		if status == NO_ROOM {
+			newDest := make([]byte, len(w.outbuf)*2)
+			copy(newDest, w.outbuf)
+			w.outbuf = newDest
+			goto retry
+		}
+
+		if status == STATE_ONLY {
+			outpos += size
+			goto retry
+		}
+
+		outpos += size
+	}
+
+	w.inbuf = w.inbuf[:0]
+	if len(p) > 0 {
+		w.inbuf = append(w.inbuf, p...)
+	}
+
+	n1, err := w.wr.Write(w.outbuf[0:outpos])
+
+	if err != nil && n1 < n {
+		n = n1
+	}
+
+	return
+}
+
+func (w *Writer) WriteRune(c rune) (size int, err error) {
+	if len(w.inbuf) > 0 {
+		// There are leftover bytes, a partial UTF-8 sequence.
+		w.inbuf = w.inbuf[:0]
+		w.WriteRune(0xfffd)
+	}
+
+	if w.outbuf == nil {
+		w.outbuf = make([]byte, 16)
+	}
+
+	outpos := 0
+
+retry:
+	size, status := w.encode(w.outbuf[outpos:], c)
+
+	if status == NO_ROOM {
+		w.outbuf = make([]byte, len(w.outbuf)*2)
+		goto retry
+	}
+
+	if status == STATE_ONLY {
+		outpos += size
+		goto retry
+	}
+
+	outpos += size
+
+	return w.wr.Write(w.outbuf[0:outpos])
+}