github.com/insionng/yougam@v0.0.0-20170714101924-2bc18d833463/libraries/mahonia/big5.go (about)

     1  package mahonia
     2  
     3  // Converters for Big 5 encoding.
     4  
     5  import (
     6  	"sync"
     7  )
     8  
     9  func init() {
    10  	RegisterCharset(&Charset{
    11  		Name:    "Big5",
    12  		Aliases: []string{"csBig5"},
    13  		NewDecoder: func() Decoder {
    14  			return decodeBig5Rune
    15  		},
    16  		NewEncoder: func() Encoder {
    17  			big5Once.Do(reverseBig5Table)
    18  			return encodeBig5Rune
    19  		},
    20  	})
    21  }
    22  
    23  func decodeBig5Rune(p []byte) (r rune, size int, status Status) {
    24  	if len(p) == 0 {
    25  		status = NO_ROOM
    26  		return
    27  	}
    28  
    29  	b := p[0]
    30  	if b < 128 {
    31  		return rune(b), 1, SUCCESS
    32  	}
    33  
    34  	if len(p) < 2 {
    35  		status = NO_ROOM
    36  		return
    37  	}
    38  
    39  	c := int(p[0])<<8 + int(p[1])
    40  	c = int(big5ToUnicode[c])
    41  	if c > 0 {
    42  		return rune(c), 2, SUCCESS
    43  	}
    44  
    45  	return 0xfffd, 1, INVALID_CHAR
    46  }
    47  
    48  func encodeBig5Rune(p []byte, r rune) (size int, status Status) {
    49  	if len(p) == 0 {
    50  		status = NO_ROOM
    51  		return
    52  	}
    53  
    54  	if r < 128 {
    55  		p[0] = byte(r)
    56  		return 1, SUCCESS
    57  	}
    58  
    59  	if len(p) < 2 {
    60  		status = NO_ROOM
    61  		return
    62  	}
    63  
    64  	if r < 0x10000 {
    65  		c := unicodeToBig5[r]
    66  		if c > 0 {
    67  			p[0] = byte(c >> 8)
    68  			p[1] = byte(c)
    69  			return 2, SUCCESS
    70  		}
    71  	}
    72  
    73  	p[0] = '?'
    74  	return 1, INVALID_CHAR
    75  }
    76  
    77  var big5Once sync.Once
    78  
    79  var unicodeToBig5 []uint16
    80  
    81  func reverseBig5Table() {
    82  	unicodeToBig5 = make([]uint16, 65536)
    83  
    84  	for big5, unicode := range big5ToUnicode {
    85  		if unicode > 0 {
    86  			unicodeToBig5[unicode] = uint16(big5)
    87  		}
    88  	}
    89  }