Add go-charset and chardet to vendor

vendor/github.com/paulrosania/go-charset/charset/cp932.go

@@ -0,0 +1,195 @@
+package charset
+
+import (
+	"fmt"
+	"unicode/utf8"
+)
+
+func init() {
+	registerClass("cp932", fromCP932, nil)
+}
+
+// encoding details
+// (Traditional) Shift-JIS
+//
+// 00..1f	control characters
+// 20		space
+// 21..7f	JIS X 0201:1976/1997 roman (see notes)
+// 80		undefined
+// 81..9f	lead byte of JIS X 0208-1983 or JIS X 0202:1990/1997
+// a0		undefined
+// a1..df	JIS X 0201:1976/1997 katakana
+// e0..ea	lead byte of JIS X 0208-1983 or JIS X 0202:1990/1997
+// eb..ff	undefined
+//
+// CP932 (windows-31J)
+//
+// this encoding scheme extends Shift-JIS in the following way
+//
+// eb..ec	undefined (marked as lead bytes - see notes below)
+// ed..ee	lead byte of NEC-selected IBM extended characters
+// ef		undefined (marked as lead byte - see notes below)
+// f0..f9	lead byte of User defined GAIJI (see note below)
+// fa..fc	lead byte of IBM extended characters
+// fd..ff	undefined
+//
+//
+// Notes
+//
+// JISX 0201:1976/1997 roman
+//	this is the same as ASCII but with 0x5c (ASCII code for '\')
+//	representing the Yen currency symbol '¥' (U+00a5)
+//	This mapping is contentious, some conversion packages implent it
+//	others do not.
+//	The mapping files from The Unicode Consortium show cp932 mapping
+//	plain ascii in the range 00..7f whereas shift-jis maps 0x5c ('\') to the yen
+//	symbol (¥) and 0x7e ('~') to overline (¯)
+//
+// CP932 double-byte character codes:
+//
+// eb-ec, ef, f0-f9:
+// 	Marked as DBCS LEAD BYTEs in the unicode mapping data
+//	obtained from:
+//		https://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP932.TXT
+//
+// 	but there are no defined mappings for codes in this range.
+// 	It is not clear whether or not an implementation should
+// 	consume one or two bytes before emitting an error char.
+
+const (
+	kanaPages    = 1
+	kanaPageSize = 63
+	kanaChar0    = 0xa1
+
+	cp932Pages    = 45  // 81..84, 87..9f, e0..ea, ed..ee, fa..fc
+	cp932PageSize = 189 // 40..fc (including 7f)
+	cp932Char0    = 0x40
+)
+
+type jisTables struct {
+	page0   [256]rune
+	dbcsoff [256]int
+	cp932   []rune
+}
+
+type translateFromCP932 struct {
+	tables  *jisTables
+	scratch []byte
+}
+
+func (p *translateFromCP932) Translate(data []byte, eof bool) (int, []byte, error) {
+	tables := p.tables
+	p.scratch = p.scratch[:0]
+	n := 0
+	for i := 0; i < len(data); i++ {
+		b := data[i]
+		r := tables.page0[b]
+		if r != -1 {
+			p.scratch = appendRune(p.scratch, r)
+			n++
+			continue
+		}
+		// DBCS
+		i++
+		if i >= len(data) {
+			break
+		}
+		pnum := tables.dbcsoff[b]
+		ix := int(data[i]) - cp932Char0
+		if pnum == -1 || ix < 0 || ix >= cp932PageSize {
+			r = utf8.RuneError
+		} else {
+			r = tables.cp932[pnum*cp932PageSize+ix]
+		}
+		p.scratch = appendRune(p.scratch, r)
+		n += 2
+	}
+	return n, p.scratch, nil
+}
+
+type cp932Key bool
+
+func fromCP932(arg string) (Translator, error) {
+	shiftJIS := arg == "shiftjis"
+	tables, err := cache(cp932Key(shiftJIS), func() (interface{}, error) {
+		tables := new(jisTables)
+		kana, err := jisGetMap("jisx0201kana.dat", kanaPageSize, kanaPages)
+		if err != nil {
+			return nil, err
+		}
+		tables.cp932, err = jisGetMap("cp932.dat", cp932PageSize, cp932Pages)
+		if err != nil {
+			return nil, err
+		}
+
+		// jisx0201kana is mapped into 0xA1..0xDF
+		for i := 0; i < kanaPageSize; i++ {
+			tables.page0[i+kanaChar0] = kana[i]
+		}
+
+		// 00..7f same as ascii in cp932
+		for i := rune(0); i < 0x7f; i++ {
+			tables.page0[i] = i
+		}
+
+		if shiftJIS {
+			// shift-jis uses JIS X 0201 for the ASCII range
+			// this is the same as ASCII apart from
+			// 0x5c ('\') maps to yen symbol (¥) and 0x7e ('~') maps to overline (¯)
+			tables.page0['\\'] = '¥'
+			tables.page0['~'] = '¯'
+		}
+
+		// pre-calculate DBCS page numbers to mapping file page numbers
+		// and mark codes in page0 that are DBCS lead bytes
+		pnum := 0
+		for i := 0x81; i <= 0x84; i++ {
+			tables.page0[i] = -1
+			tables.dbcsoff[i] = pnum
+			pnum++
+		}
+		for i := 0x87; i <= 0x9f; i++ {
+			tables.page0[i] = -1
+			tables.dbcsoff[i] = pnum
+			pnum++
+		}
+		for i := 0xe0; i <= 0xea; i++ {
+			tables.page0[i] = -1
+			tables.dbcsoff[i] = pnum
+			pnum++
+		}
+		if shiftJIS {
+			return tables, nil
+		}
+		// add in cp932 extensions
+		for i := 0xed; i <= 0xee; i++ {
+			tables.page0[i] = -1
+			tables.dbcsoff[i] = pnum
+			pnum++
+		}
+		for i := 0xfa; i <= 0xfc; i++ {
+			tables.page0[i] = -1
+			tables.dbcsoff[i] = pnum
+			pnum++
+		}
+		return tables, nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &translateFromCP932{tables: tables.(*jisTables)}, nil
+}
+
+func jisGetMap(name string, pgsize, npages int) ([]rune, error) {
+	data, err := readFile(name)
+	if err != nil {
+		return nil, err
+	}
+	m := []rune(string(data))
+	if len(m) != pgsize*npages {
+		return nil, fmt.Errorf("%q: incorrect length data", name)
+	}
+	return m, nil
+}