1 files changed, 89 insertions, 0 deletions
diff --git a/modules/mahonia/big5.go b/modules/mahonia/big5.go
new file mode 100644
index 0000000000..07044fe9e2
--- /dev/null
+++ b/modules/mahonia/big5.go
@@ -0,0 +1,89 @@
+package mahonia
+
+// Converters for Big 5 encoding.
+
+import (
+	"sync"
+)
+
+func init() {
+	RegisterCharset(&Charset{
+		Name:    "Big5",
+		Aliases: []string{"csBig5"},
+		NewDecoder: func() Decoder {
+			return decodeBig5Rune
+		},
+		NewEncoder: func() Encoder {
+			big5Once.Do(reverseBig5Table)
+			return encodeBig5Rune
+		},
+	})
+}
+
+func decodeBig5Rune(p []byte) (r rune, size int, status Status) {
+	if len(p) == 0 {
+		status = NO_ROOM
+		return
+	}
+
+	b := p[0]
+	if b < 128 {
+		return rune(b), 1, SUCCESS
+	}
+
+	if len(p) < 2 {
+		status = NO_ROOM
+		return
+	}
+
+	c := int(p[0])<<8 + int(p[1])
+	c = int(big5ToUnicode[c])
+	if c > 0 {
+		return rune(c), 2, SUCCESS
+	}
+
+	return 0xfffd, 1, INVALID_CHAR
+}
+
+func encodeBig5Rune(p []byte, r rune) (size int, status Status) {
+	if len(p) == 0 {
+		status = NO_ROOM
+		return
+	}
+
+	if r < 128 {
+		p[0] = byte(r)
+		return 1, SUCCESS
+	}
+
+	if len(p) < 2 {
+		status = NO_ROOM
+		return
+	}
+
+	if r < 0x10000 {
+		c := unicodeToBig5[r]
+		if c > 0 {
+			p[0] = byte(c >> 8)
+			p[1] = byte(c)
+			return 2, SUCCESS
+		}
+	}
+
+	p[0] = '?'
+	return 1, INVALID_CHAR
+}
+
+var big5Once sync.Once
+
+var unicodeToBig5 []uint16
+
+func reverseBig5Table() {
+	unicodeToBig5 = make([]uint16, 65536)
+
+	for big5, unicode := range big5ToUnicode {
+		if unicode > 0 {
+			unicodeToBig5[unicode] = uint16(big5)
+		}
+	}
+}