import ChecksumException from '../../ChecksumException';
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import GenericGF from '../../common/reedsolomon/GenericGF';
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import ReedSolomonDecoder from '../../common/reedsolomon/ReedSolomonDecoder';
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import BitMatrixParser from './BitMatrixParser';
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import DataBlock from './DataBlock';
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import DecodedBitStreamParser from './DecodedBitStreamParser';
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/*
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* Copyright 2007 ZXing authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* <p>The main class which implements Data Matrix Code decoding -- as opposed to locating and extracting
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* the Data Matrix Code from an image.</p>
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*
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* @author bbrown@google.com (Brian Brown)
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*/
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export default class Decoder {
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constructor() {
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this.rsDecoder = new ReedSolomonDecoder(GenericGF.DATA_MATRIX_FIELD_256);
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}
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/**
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* <p>Decodes a Data Matrix Code represented as a {@link BitMatrix}. A 1 or "true" is taken
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* to mean a black module.</p>
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*
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* @param bits booleans representing white/black Data Matrix Code modules
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* @return text and bytes encoded within the Data Matrix Code
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* @throws FormatException if the Data Matrix Code cannot be decoded
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* @throws ChecksumException if error correction fails
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*/
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decode(bits) {
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// Construct a parser and read version, error-correction level
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const parser = new BitMatrixParser(bits);
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const version = parser.getVersion();
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// Read codewords
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const codewords = parser.readCodewords();
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// Separate into data blocks
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const dataBlocks = DataBlock.getDataBlocks(codewords, version);
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// Count total number of data bytes
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let totalBytes = 0;
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for (let db of dataBlocks) {
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totalBytes += db.getNumDataCodewords();
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}
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const resultBytes = new Uint8Array(totalBytes);
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const dataBlocksCount = dataBlocks.length;
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// Error-correct and copy data blocks together into a stream of bytes
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for (let j = 0; j < dataBlocksCount; j++) {
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const dataBlock = dataBlocks[j];
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const codewordBytes = dataBlock.getCodewords();
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const numDataCodewords = dataBlock.getNumDataCodewords();
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this.correctErrors(codewordBytes, numDataCodewords);
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for (let i = 0; i < numDataCodewords; i++) {
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// De-interlace data blocks.
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resultBytes[i * dataBlocksCount + j] = codewordBytes[i];
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}
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}
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// Decode the contents of that stream of bytes
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return DecodedBitStreamParser.decode(resultBytes);
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}
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/**
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* <p>Given data and error-correction codewords received, possibly corrupted by errors, attempts to
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* correct the errors in-place using Reed-Solomon error correction.</p>
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*
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* @param codewordBytes data and error correction codewords
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* @param numDataCodewords number of codewords that are data bytes
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* @throws ChecksumException if error correction fails
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*/
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correctErrors(codewordBytes, numDataCodewords) {
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// const numCodewords = codewordBytes.length;
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// First read into an array of ints
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const codewordsInts = new Int32Array(codewordBytes);
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// for (let i = 0; i < numCodewords; i++) {
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// codewordsInts[i] = codewordBytes[i] & 0xFF;
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// }
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try {
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this.rsDecoder.decode(codewordsInts, codewordBytes.length - numDataCodewords);
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}
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catch (ignored /* ReedSolomonException */) {
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throw new ChecksumException();
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}
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// Copy back into array of bytes -- only need to worry about the bytes that were data
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// We don't care about errors in the error-correction codewords
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for (let i = 0; i < numDataCodewords; i++) {
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codewordBytes[i] = codewordsInts[i];
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}
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}
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}
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