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