Final touches for combining character support

pkg/highlight/unicode.go

@@ -0,0 +1,86 @@
+package highlight
+
+import (
+	"unicode"
+	"unicode/utf8"
+)
+
+// combining character range table
+var combining = &unicode.RangeTable{
+	R16: []unicode.Range16{
+		{0x0300, 0x036f, 1}, // combining diacritical marks
+		{0x1ab0, 0x1aff, 1}, // combining diacritical marks extended
+		{0x1dc0, 0x1dff, 1}, // combining diacritical marks supplement
+		{0x20d0, 0x20ff, 1}, // combining diacritical marks for symbols
+		{0xfe20, 0xfe2f, 1}, // combining half marks
+	},
+}
+
+// DecodeCharacter returns the next character from an array of bytes
+// A character is a rune along with any accompanying combining runes
+func DecodeCharacter(b []byte) (rune, []rune, int) {
+	r, size := utf8.DecodeRune(b)
+	b = b[size:]
+	c, s := utf8.DecodeRune(b)
+
+	var combc []rune
+	for unicode.In(c, combining) {
+		combc = append(combc, c)
+		size += s
+
+		b = b[s:]
+		c, s = utf8.DecodeRune(b)
+	}
+
+	return r, combc, size
+}
+
+// DecodeCharacterInString returns the next character from a string
+// A character is a rune along with any accompanying combining runes
+func DecodeCharacterInString(str string) (rune, []rune, int) {
+	r, size := utf8.DecodeRuneInString(str)
+	str = str[size:]
+	c, s := utf8.DecodeRuneInString(str)
+
+	var combc []rune
+	for unicode.In(c, combining) {
+		combc = append(combc, c)
+		size += s
+
+		str = str[s:]
+		c, s = utf8.DecodeRuneInString(str)
+	}
+
+	return r, combc, size
+}
+
+// CharacterCount returns the number of characters in a byte array
+// Similar to utf8.RuneCount but for unicode characters
+func CharacterCount(b []byte) int {
+	s := 0
+
+	for len(b) > 0 {
+		r, size := utf8.DecodeRune(b)
+		if !unicode.In(r, combining) {
+			s++
+		}
+
+		b = b[size:]
+	}
+
+	return s
+}
+
+// CharacterCount returns the number of characters in a string
+// Similar to utf8.RuneCountInString but for unicode characters
+func CharacterCountInString(str string) int {
+	s := 0
+
+	for _, r := range str {
+		if !unicode.In(r, combining) {
+			s++
+		}
+	}
+
+	return s
+}