96 lines
1.9 KiB
Go
96 lines
1.9 KiB
Go
package table
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import (
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"bytes"
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"errors"
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"fmt"
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"unicode/utf8"
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"golang.org/x/text/unicode/norm"
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"moria.us/macscript/charmap"
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)
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// An UnsupportedError indicates that the charmap is not supported by the
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// conversion routines.
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type UnsupportedError struct {
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Message string
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}
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func (e *UnsupportedError) Error() string {
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return "unsupported charmap: " + e.Message
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}
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// Table type identifiers.
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const (
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extendedASCIITable = iota + 1
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)
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type Table interface {
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Data() []byte
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}
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func Create(m *charmap.Charmap) (Table, error) {
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if m.OneByte == nil {
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return nil, errors.New("missing one-byte map")
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}
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if m.TwoByte != nil {
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return nil, &UnsupportedError{"multibyte encoding"}
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}
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if m.Digraph != nil {
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return nil, &UnsupportedError{"contains digraphs"}
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}
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var t ExtendedASCII
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for c, e := range m.OneByte {
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if e.Direction != charmap.DirectionAny {
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return nil, &UnsupportedError{
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fmt.Sprintf("character has bidirectional context: 0x%02x", c)}
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}
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var u rune
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switch len(e.Unicode) {
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case 0:
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case 1:
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u = e.Unicode[0]
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default:
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return nil, &UnsupportedError{
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fmt.Sprintf("character maps to multiple code points: 0x%02x", c)}
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}
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if c < 128 {
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if u != rune(c) {
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return nil, &UnsupportedError{
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fmt.Sprintf("character is not equal to ASCII equivalent: 0x%02x", c)}
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}
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} else {
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t.HighCharacters[c-128] = u
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}
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}
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return &t, nil
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}
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// An ExtendedASCII is a table for converting from extended ASCII.
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type ExtendedASCII struct {
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HighCharacters [128]rune
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}
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func (t *ExtendedASCII) Data() []byte {
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var ubuf [4]byte
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var nbuf [16]byte
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d := []byte{extendedASCIITable}
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for _, u := range t.HighCharacters {
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var udata, ndata []byte
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if u != 0 {
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n := utf8.EncodeRune(ubuf[:], u)
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udata = ubuf[:n]
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ndata = norm.NFD.Append(nbuf[:0], udata...)
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if bytes.Equal(udata, ndata) {
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ndata = nil
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}
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}
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d = append(d, byte(len(udata)))
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d = append(d, udata...)
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d = append(d, byte(len(ndata)))
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d = append(d, ndata...)
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}
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return d
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}
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