@kayahr/text-encoding
Version:
Text encoder and decoder
57 lines • 1.88 kB
JavaScript
/*
* Copyright (C) 2021 Klaus Reimer <k@ailis.de>
* See LICENSE.md for licensing information.
*/
import big5 from "../../../data/big5.cp.js";
import { AbstractDecoder } from "../AbstractDecoder.js";
import { END_OF_BUFFER } from "../ByteBuffer.js";
import { FINISHED } from "../constants.js";
import { inRange, isASCII } from "../util.js";
/**
* Decoder for big5 encoding.
*/
export class Big5Decoder extends AbstractDecoder {
lead = 0x00;
/** @inheritdoc */
decode(buffer) {
const byte = buffer.read();
if (byte === END_OF_BUFFER && this.lead !== 0x00) {
this.lead = 0x00;
return this.fail();
}
if (byte === END_OF_BUFFER && this.lead === 0x00) {
return FINISHED;
}
if (this.lead !== 0x00) {
const lead = this.lead;
this.lead = 0x00;
const offset = byte < 0x7F ? 0x40 : 0x62;
let index = null;
if (inRange(byte, 0x40, 0x7E) || inRange(byte, 0xA1, 0xFE)) {
index = (lead - 0x81) * 157 + (byte - offset);
}
switch (index) {
case 1133: return [0x00CA, 0x0304];
case 1135: return [0x00CA, 0x030C];
case 1164: return [0x00EA, 0x0304];
case 1166: return [0x00EA, 0x030C];
case null:
default:
}
const codePoint = (index == null) ? null : big5[index] ?? null;
if (codePoint == null && isASCII(byte)) {
buffer.write(byte);
}
return codePoint ?? this.fail();
}
if (isASCII(byte)) {
return byte;
}
if (inRange(byte, 0x81, 0xFE)) {
this.lead = byte;
return null;
}
return this.fail();
}
}
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