1 files changed, 170 insertions, 0 deletions
diff --git a/modules/mahonia/utf16.go b/modules/mahonia/utf16.go
new file mode 100644
index 00000000..3ec7b770
--- /dev/null
+++ b/modules/mahonia/utf16.go
@@ -0,0 +1,170 @@
+package mahonia
+
+import (
+	"unicode/utf16"
+)
+
+func init() {
+	for i := 0; i < len(utf16Charsets); i++ {
+		RegisterCharset(&utf16Charsets[i])
+	}
+}
+
+var utf16Charsets = []Charset{
+	{
+		Name: "UTF-16",
+		NewDecoder: func() Decoder {
+			var decodeRune Decoder
+			return func(p []byte) (c rune, size int, status Status) {
+				if decodeRune == nil {
+					// haven't read the BOM yet
+					if len(p) < 2 {
+						status = NO_ROOM
+						return
+					}
+
+					switch {
+					case p[0] == 0xfe && p[1] == 0xff:
+						decodeRune = decodeUTF16beRune
+						return 0, 2, STATE_ONLY
+					case p[0] == 0xff && p[1] == 0xfe:
+						decodeRune = decodeUTF16leRune
+						return 0, 2, STATE_ONLY
+					default:
+						decodeRune = decodeUTF16beRune
+					}
+				}
+
+				return decodeRune(p)
+			}
+		},
+		NewEncoder: func() Encoder {
+			wroteBOM := false
+			return func(p []byte, c rune) (size int, status Status) {
+				if !wroteBOM {
+					if len(p) < 2 {
+						status = NO_ROOM
+						return
+					}
+
+					p[0] = 0xfe
+					p[1] = 0xff
+					wroteBOM = true
+					return 2, STATE_ONLY
+				}
+
+				return encodeUTF16beRune(p, c)
+			}
+		},
+	},
+	{
+		Name:       "UTF-16BE",
+		NewDecoder: func() Decoder { return decodeUTF16beRune },
+		NewEncoder: func() Encoder { return encodeUTF16beRune },
+	},
+	{
+		Name:       "UTF-16LE",
+		NewDecoder: func() Decoder { return decodeUTF16leRune },
+		NewEncoder: func() Encoder { return encodeUTF16leRune },
+	},
+}
+
+func decodeUTF16beRune(p []byte) (r rune, size int, status Status) {
+	if len(p) < 2 {
+		status = NO_ROOM
+		return
+	}
+
+	c := rune(p[0])<<8 + rune(p[1])
+
+	if utf16.IsSurrogate(c) {
+		if len(p) < 4 {
+			status = NO_ROOM
+			return
+		}
+
+		c2 := rune(p[2])<<8 + rune(p[3])
+		c = utf16.DecodeRune(c, c2)
+
+		if c == 0xfffd {
+			return c, 2, INVALID_CHAR
+		} else {
+			return c, 4, SUCCESS
+		}
+	}
+
+	return c, 2, SUCCESS
+}
+
+func encodeUTF16beRune(p []byte, c rune) (size int, status Status) {
+	if c < 0x10000 {
+		if len(p) < 2 {
+			status = NO_ROOM
+			return
+		}
+		p[0] = byte(c >> 8)
+		p[1] = byte(c)
+		return 2, SUCCESS
+	}
+
+	if len(p) < 4 {
+		status = NO_ROOM
+		return
+	}
+	s1, s2 := utf16.EncodeRune(c)
+	p[0] = byte(s1 >> 8)
+	p[1] = byte(s1)
+	p[2] = byte(s2 >> 8)
+	p[3] = byte(s2)
+	return 4, SUCCESS
+}
+
+func decodeUTF16leRune(p []byte) (r rune, size int, status Status) {
+	if len(p) < 2 {
+		status = NO_ROOM
+		return
+	}
+
+	c := rune(p[1])<<8 + rune(p[0])
+
+	if utf16.IsSurrogate(c) {
+		if len(p) < 4 {
+			status = NO_ROOM
+			return
+		}
+
+		c2 := rune(p[3])<<8 + rune(p[2])
+		c = utf16.DecodeRune(c, c2)
+
+		if c == 0xfffd {
+			return c, 2, INVALID_CHAR
+		} else {
+			return c, 4, SUCCESS
+		}
+	}
+
+	return c, 2, SUCCESS
+}
+
+func encodeUTF16leRune(p []byte, c rune) (size int, status Status) {
+	if c < 0x10000 {
+		if len(p) < 2 {
+			status = NO_ROOM
+			return
+		}
+		p[1] = byte(c >> 8)
+		p[0] = byte(c)
+		return 2, SUCCESS
+	}
+
+	if len(p) < 4 {
+		status = NO_ROOM
+		return
+	}
+	s1, s2 := utf16.EncodeRune(c)
+	p[1] = byte(s1 >> 8)
+	p[0] = byte(s1)
+	p[3] = byte(s2 >> 8)
+	p[2] = byte(s2)
+	return 4, SUCCESS
+}