@zxing/text-encoding
Version:
Polyfill for the Encoding Living Standard's API.
95 lines • 4.16 kB
JavaScript
import { decoderError } from "../../encoding/encodings";
import { finished } from "../../encoding/finished";
import { index, indexCodePointFor } from "../../encoding/indexes";
import { end_of_stream, isASCIIByte } from "../../encoding/terminology";
import { inRange } from "../../encoding/utilities";
/**
* @constructor
* @implements {Decoder}
* @param {{fatal: boolean}} options
*/
var Big5Decoder = /** @class */ (function () {
function Big5Decoder(options) {
this.fatal = options.fatal;
// Big5's decoder has an associated Big5 lead (initially 0x00).
/** @type {number} */ this.Big5_lead = 0x00;
}
/**
* @param {Stream} stream The stream of bytes being decoded.
* @param {number} bite The next byte read from the stream.
* @return {?(number|!Array.<number>)} The next code point(s)
* decoded, or null if not enough data exists in the input
* stream to decode a complete code point.
*/
Big5Decoder.prototype.handler = function (stream, bite) {
// 1. If byte is end-of-stream and Big5 lead is not 0x00, set
// Big5 lead to 0x00 and return error.
if (bite === end_of_stream && this.Big5_lead !== 0x00) {
this.Big5_lead = 0x00;
return decoderError(this.fatal);
}
// 2. If byte is end-of-stream and Big5 lead is 0x00, return
// finished.
if (bite === end_of_stream && this.Big5_lead === 0x00)
return finished;
// 3. If Big5 lead is not 0x00, let lead be Big5 lead, let
// pointer be null, set Big5 lead to 0x00, and then run these
// substeps:
if (this.Big5_lead !== 0x00) {
var lead = this.Big5_lead;
var pointer = null;
this.Big5_lead = 0x00;
// 1. Let offset be 0x40 if byte is less than 0x7F and 0x62
// otherwise.
var offset = bite < 0x7F ? 0x40 : 0x62;
// 2. If byte is in the range 0x40 to 0x7E, inclusive, or 0xA1
// to 0xFE, inclusive, set pointer to (lead − 0x81) × 157 +
// (byte − offset).
if (inRange(bite, 0x40, 0x7E) || inRange(bite, 0xA1, 0xFE))
pointer = (lead - 0x81) * 157 + (bite - offset);
// 3. If there is a row in the table below whose first column
// is pointer, return the two code points listed in its second
// column
// Pointer | Code points
// --------+--------------
// 1133 | U+00CA U+0304
// 1135 | U+00CA U+030C
// 1164 | U+00EA U+0304
// 1166 | U+00EA U+030C
switch (pointer) {
case 1133: return [0x00CA, 0x0304];
case 1135: return [0x00CA, 0x030C];
case 1164: return [0x00EA, 0x0304];
case 1166: return [0x00EA, 0x030C];
}
// 4. Let code point be null if pointer is null and the index
// code point for pointer in index Big5 otherwise.
var code_point = (pointer === null) ? null :
indexCodePointFor(pointer, index('big5'));
// 5. If code point is null and byte is an ASCII byte, prepend
// byte to stream.
if (code_point === null && isASCIIByte(bite))
stream.prepend(bite);
// 6. If code point is null, return error.
if (code_point === null)
return decoderError(this.fatal);
// 7. Return a code point whose value is code point.
return code_point;
}
// 4. If byte is an ASCII byte, return a code point whose value
// is byte.
if (isASCIIByte(bite))
return bite;
// 5. If byte is in the range 0x81 to 0xFE, inclusive, set Big5
// lead to byte and return continue.
if (inRange(bite, 0x81, 0xFE)) {
this.Big5_lead = bite;
return null;
}
// 6. Return error.
return decoderError(this.fatal);
};
return Big5Decoder;
}());
export { Big5Decoder };
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