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big5.go
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big5.go
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package mahonia
// Converters for Big 5 encoding.
import (
"sync"
)
func init() {
RegisterCharset(&Charset{
Name: "Big5",
Aliases: []string{"csBig5"},
NewDecoder: func() Decoder {
return decodeBig5Rune
},
NewEncoder: func() Encoder {
big5Once.Do(reverseBig5Table)
return encodeBig5Rune
},
})
}
func decodeBig5Rune(p []byte) (r rune, size int, status Status) {
if len(p) == 0 {
status = NO_ROOM
return
}
b := p[0]
if b < 128 {
return rune(b), 1, SUCCESS
}
if len(p) < 2 {
status = NO_ROOM
return
}
c := int(p[0])<<8 + int(p[1])
c = int(big5ToUnicode[c])
if c > 0 {
return rune(c), 2, SUCCESS
}
return 0xfffd, 1, INVALID_CHAR
}
func encodeBig5Rune(p []byte, r rune) (size int, status Status) {
if len(p) == 0 {
status = NO_ROOM
return
}
if r < 128 {
p[0] = byte(r)
return 1, SUCCESS
}
if len(p) < 2 {
status = NO_ROOM
return
}
if r < 0x10000 {
c := unicodeToBig5[r]
if c > 0 {
p[0] = byte(c >> 8)
p[1] = byte(c)
return 2, SUCCESS
}
}
p[0] = '?'
return 1, INVALID_CHAR
}
var big5Once sync.Once
var unicodeToBig5 []uint16
func reverseBig5Table() {
unicodeToBig5 = make([]uint16, 65536)
for big5, unicode := range big5ToUnicode {
if unicode > 0 {
unicodeToBig5[unicode] = uint16(big5)
}
}
}