v3-h5-web/node_modules/@zxing/text-encoding/es2015/coders/big5/Big5Decoder.js

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
  */
export class Big5Decoder {
    constructor(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.
     */
    handler(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) {
            const lead = this.Big5_lead;
            let pointer = null;
            this.Big5_lead = 0x00;
            // 1. Let offset be 0x40 if byte is less than 0x7F and 0x62
            // otherwise.
            const 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.
            const 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);
    }
}
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