89 lines
2.1 KiB
Go
89 lines
2.1 KiB
Go
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package mahonia
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import (
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"sync"
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"unicode/utf8"
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)
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// A kutenTable holds the data for a double-byte character set, arranged by ku
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// (区, zone) and ten (点, position). These can be converted to various actual
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// encoding schemes.
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type kutenTable struct {
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// Data[ku][ten] is the unicode value for the character at that zone and
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// position.
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Data [94][94]uint16
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// FromUnicode holds the ku and ten for each Unicode code point.
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// It is not available until Reverse() has been called.
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FromUnicode [][2]byte
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// once is used to synchronize the generation of FromUnicode.
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once sync.Once
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}
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// Reverse generates FromUnicode.
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func (t *kutenTable) Reverse() {
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t.once.Do(func() {
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t.FromUnicode = make([][2]byte, 65536)
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for ku := range t.Data {
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for ten, unicode := range t.Data[ku] {
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t.FromUnicode[unicode] = [2]byte{byte(ku), byte(ten)}
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}
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}
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})
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}
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// DecodeLow decodes a character from an encoding that does not have the high
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// bit set.
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func (t *kutenTable) DecodeLow(p []byte) (c rune, size int, status Status) {
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if len(p) < 2 {
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return 0, 0, NO_ROOM
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}
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ku := p[0] - 0x21
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ten := p[1] - 0x21
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if ku > 93 || ten > 93 {
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return utf8.RuneError, 1, INVALID_CHAR
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}
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u := t.Data[ku][ten]
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if u == 0 {
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return utf8.RuneError, 1, INVALID_CHAR
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}
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return rune(u), 2, SUCCESS
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}
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// DecodeHigh decodes a character from an encoding that has the high bit set.
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func (t *kutenTable) DecodeHigh(p []byte) (c rune, size int, status Status) {
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if len(p) < 2 {
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return 0, 0, NO_ROOM
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}
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ku := p[0] - 0xa1
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ten := p[1] - 0xa1
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if ku > 93 || ten > 93 {
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return utf8.RuneError, 1, INVALID_CHAR
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}
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u := t.Data[ku][ten]
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if u == 0 {
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return utf8.RuneError, 1, INVALID_CHAR
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}
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return rune(u), 2, SUCCESS
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}
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// EncodeHigh encodes a character in an encoding that has the high bit set.
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func (t *kutenTable) EncodeHigh(p []byte, c rune) (size int, status Status) {
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if len(p) < 2 {
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return 0, NO_ROOM
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}
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if c > 0xffff {
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p[0] = '?'
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return 1, INVALID_CHAR
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}
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kuten := t.FromUnicode[c]
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if kuten == [2]byte{0, 0} && c != rune(t.Data[0][0]) {
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p[0] = '?'
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return 1, INVALID_CHAR
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}
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p[0] = kuten[0] + 0xa1
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p[1] = kuten[1] + 0xa1
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return 2, SUCCESS
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}
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