@nuintun/qrcode/cjs/decoder/utils/decoder.cjs

A pure JavaScript QRCode encode and decode library.

/**
 * @module QRCode
 * @package @nuintun/qrcode
 * @license MIT
 * @version 5.0.2
 * @author nuintun <nuintun@qq.com>
 * @description A pure JavaScript QRCode encode and decode library.
 * @see https://github.com/nuintun/qrcode#readme
 */

'use strict';

const DataBlock = require('../DataBlock.cjs');
const Decoder = require('../../common/reedsolomon/Decoder.cjs');

/**
 * @module decoder
 */
function correctErrors(codewords, numDataCodewords) {
  const buffer = new Int32Array(codewords);
  const numECCodewords = codewords.length - numDataCodewords;
  // Reed solomon encode.
  const errorsCorrected = new Decoder.Decoder().decode(buffer, numECCodewords);
  return [buffer, errorsCorrected];
}
function getDataBlocks(codewords, version, ecLevel) {
  const { ecBlocks, numTotalCodewords, numECCodewordsPerBlock } = version.getECBlocks(ecLevel);
  if (codewords.length !== numTotalCodewords) {
    throw new Error('failed to get data blocks');
  }
  const blocks = [];
  // Now establish DataBlocks of the appropriate size and number of data codewords.
  for (const { count, numDataCodewords } of ecBlocks) {
    for (let i = 0; i < count; i++) {
      const numBlockCodewords = numECCodewordsPerBlock + numDataCodewords;
      blocks.push(new DataBlock.DataBlock(new Uint8Array(numBlockCodewords), numDataCodewords));
    }
  }
  const { length } = blocks;
  // All blocks have the same amount of data, except that the last n
  // (where n may be 0) have 1 more byte. Figure out where these start.
  let longerBlocksStartAt = length - 1;
  const shorterBlocksTotalCodewords = blocks[0].codewords.length;
  while (longerBlocksStartAt >= 0) {
    const numCodewords = blocks[longerBlocksStartAt].codewords.length;
    if (numCodewords === shorterBlocksTotalCodewords) {
      break;
    }
    longerBlocksStartAt--;
  }
  longerBlocksStartAt++;
  // The last elements of result may be 1 element longer;
  // first fill out as many elements as all of them have.
  let codewordsOffset = 0;
  const shorterBlocksNumDataCodewords = shorterBlocksTotalCodewords - numECCodewordsPerBlock;
  for (let i = 0; i < shorterBlocksNumDataCodewords; i++) {
    for (let j = 0; j < length; j++) {
      blocks[j].codewords[i] = codewords[codewordsOffset++];
    }
  }
  // Fill out the last data block in the longer ones.
  for (let j = longerBlocksStartAt; j < length; j++) {
    blocks[j].codewords[shorterBlocksNumDataCodewords] = codewords[codewordsOffset++];
  }
  // Now add in error correction blocks.
  const max = blocks[0].codewords.length;
  for (let i = shorterBlocksNumDataCodewords; i < max; i++) {
    for (let j = 0; j < length; j++) {
      const offset = j < longerBlocksStartAt ? i : i + 1;
      blocks[j].codewords[offset] = codewords[codewordsOffset++];
    }
  }
  return blocks;
}

exports.correctErrors = correctErrors;
exports.getDataBlocks = getDataBlocks;