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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
}
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