syncfiles/gen/table/table.go
Dietrich Epp f94a65d245 Generate conversion data for extended ASCII
This creates conversion tables for 11 of the 21 character sets.
2022-03-15 16:19:56 -04:00

96 lines
1.9 KiB
Go

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