Add ISO-2022 charset recognizers

Author: saintfish

2022.go

@@ -0,0 +1,102 @@
+package chardet
+
+import (
+	"bytes"
+)
+
+type recognizer2022 struct {
+	charset string
+	escapes [][]byte
+}
+
+func (r *recognizer2022) Match(input *recognizerInput) (output recognizerOutput) {
+	return recognizerOutput{
+		Charset:    r.charset,
+		Confidence: r.matchConfidence(input.input),
+	}
+}
+
+func (r *recognizer2022) matchConfidence(input []byte) int {
+	var hits, misses, shifts int
+input:
+	for i := 0; i < len(input); i++ {
+		c := input[i]
+		if c == 0x1B {
+			for _, esc := range r.escapes {
+				if bytes.HasPrefix(input[i+1:], esc) {
+					hits++
+					i += len(esc)
+					continue input
+				}
+			}
+			misses++
+		} else if c == 0x0E || c == 0x0F {
+			shifts++
+		}
+	}
+	if hits == 0 {
+		return 0
+	}
+	quality := (100*hits - 100*misses) / (hits + misses)
+	if hits+shifts < 5 {
+		quality -= (5 - (hits + shifts)) * 10
+	}
+	if quality < 0 {
+		quality = 0
+	}
+	return quality
+}
+
+var escapeSequences_2022JP = [][]byte{
+	{0x24, 0x28, 0x43}, // KS X 1001:1992
+	{0x24, 0x28, 0x44}, // JIS X 212-1990
+	{0x24, 0x40},       // JIS C 6226-1978
+	{0x24, 0x41},       // GB 2312-80
+	{0x24, 0x42},       // JIS X 208-1983
+	{0x26, 0x40},       // JIS X 208 1990, 1997
+	{0x28, 0x42},       // ASCII
+	{0x28, 0x48},       // JIS-Roman
+	{0x28, 0x49},       // Half-width katakana
+	{0x28, 0x4a},       // JIS-Roman
+	{0x2e, 0x41},       // ISO 8859-1
+	{0x2e, 0x46},       // ISO 8859-7
+}
+
+var escapeSequences_2022KR = [][]byte{
+	{0x24, 0x29, 0x43},
+}
+
+var escapeSequences_2022CN = [][]byte{
+	{0x24, 0x29, 0x41}, // GB 2312-80
+	{0x24, 0x29, 0x47}, // CNS 11643-1992 Plane 1
+	{0x24, 0x2A, 0x48}, // CNS 11643-1992 Plane 2
+	{0x24, 0x29, 0x45}, // ISO-IR-165
+	{0x24, 0x2B, 0x49}, // CNS 11643-1992 Plane 3
+	{0x24, 0x2B, 0x4A}, // CNS 11643-1992 Plane 4
+	{0x24, 0x2B, 0x4B}, // CNS 11643-1992 Plane 5
+	{0x24, 0x2B, 0x4C}, // CNS 11643-1992 Plane 6
+	{0x24, 0x2B, 0x4D}, // CNS 11643-1992 Plane 7
+	{0x4e},             // SS2
+	{0x4f},             // SS3
+}
+
+func newRecognizer_2022JP() *recognizer2022 {
+	return &recognizer2022{
+		"ISO-2022-JP",
+		escapeSequences_2022JP,
+	}
+}
+
+func newRecognizer_2022KR() *recognizer2022 {
+	return &recognizer2022{
+		"ISO-2022-KR",
+		escapeSequences_2022KR,
+	}
+}
+
+func newRecognizer_2022CN() *recognizer2022 {
+	return &recognizer2022{
+		"ISO-2022-CN",
+		escapeSequences_2022CN,
+	}
+}

detector.go

@@ -52,9 +52,9 @@ var recognizers = []recognizer{
 	newRecognizer_euc_kr(),
 	newRecognizer_big5(),
 
-	// newRecognizer_2022JP(),
-	// newRecognizer_2022KR(),
-	// newRecognizer_2022CN(),
+	newRecognizer_2022JP(),
+	newRecognizer_2022KR(),
+	newRecognizer_2022CN(),
 
 	newRecognizer_IBM424_he_rtl(),
 	newRecognizer_IBM424_he_ltr(),