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124 lines
4.5 KiB
Java
124 lines
4.5 KiB
Java
/*
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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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package com.google.zxing.qrcode.decoder;
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/**
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* <p>Encapsulates a block of data within a QR Code. QR Codes may split their data into
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* multiple blocks, each of which is a unit of data and error-correction codewords. Each
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* is represented by an instance of this class.</p>
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*
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* @author Sean Owen
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*/
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final class DataBlock {
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private final int numDataCodewords;
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private final byte[] codewords;
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private DataBlock(int numDataCodewords, byte[] codewords) {
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this.numDataCodewords = numDataCodewords;
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this.codewords = codewords;
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}
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/**
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* <p>When QR Codes use multiple data blocks, they are actually interleaved.
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* That is, the first byte of data block 1 to n is written, then the second bytes, and so on. This
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* method will separate the data into original blocks.</p>
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*
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* @param rawCodewords bytes as read directly from the QR Code
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* @param version version of the QR Code
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* @param ecLevel error-correction level of the QR Code
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* @return {@link DataBlock}s containing original bytes, "de-interleaved" from representation in the
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* QR Code
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*/
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static DataBlock[] getDataBlocks(byte[] rawCodewords,
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Version version,
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ErrorCorrectionLevel ecLevel) {
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if (rawCodewords.length != version.getTotalCodewords()) {
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throw new IllegalArgumentException();
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}
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// Figure out the number and size of data blocks used by this version and
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// error correction level
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Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);
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// First count the total number of data blocks
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int totalBlocks = 0;
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Version.ECB[] ecBlockArray = ecBlocks.getECBlocks();
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for (int i = 0; i < ecBlockArray.length; i++) {
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totalBlocks += ecBlockArray[i].getCount();
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}
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// Now establish DataBlocks of the appropriate size and number of data codewords
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DataBlock[] result = new DataBlock[totalBlocks];
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int numResultBlocks = 0;
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for (int j = 0; j < ecBlockArray.length; j++) {
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Version.ECB ecBlock = ecBlockArray[j];
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for (int i = 0; i < ecBlock.getCount(); i++) {
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int numDataCodewords = ecBlock.getDataCodewords();
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int numBlockCodewords = ecBlocks.getECCodewordsPerBlock() + numDataCodewords;
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result[numResultBlocks++] = new DataBlock(numDataCodewords, new byte[numBlockCodewords]);
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}
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}
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// All blocks have the same amount of data, except that the last n
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// (where n may be 0) have 1 more byte. Figure out where these start.
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int shorterBlocksTotalCodewords = result[0].codewords.length;
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int longerBlocksStartAt = result.length - 1;
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while (longerBlocksStartAt >= 0) {
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int numCodewords = result[longerBlocksStartAt].codewords.length;
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if (numCodewords == shorterBlocksTotalCodewords) {
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break;
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}
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longerBlocksStartAt--;
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}
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longerBlocksStartAt++;
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int shorterBlocksNumDataCodewords = shorterBlocksTotalCodewords - ecBlocks.getECCodewordsPerBlock();
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// The last elements of result may be 1 element longer;
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// first fill out as many elements as all of them have
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int rawCodewordsOffset = 0;
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for (int i = 0; i < shorterBlocksNumDataCodewords; i++) {
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for (int j = 0; j < numResultBlocks; j++) {
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result[j].codewords[i] = rawCodewords[rawCodewordsOffset++];
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}
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}
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// Fill out the last data block in the longer ones
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for (int j = longerBlocksStartAt; j < numResultBlocks; j++) {
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result[j].codewords[shorterBlocksNumDataCodewords] = rawCodewords[rawCodewordsOffset++];
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}
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// Now add in error correction blocks
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int max = result[0].codewords.length;
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for (int i = shorterBlocksNumDataCodewords; i < max; i++) {
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for (int j = 0; j < numResultBlocks; j++) {
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int iOffset = j < longerBlocksStartAt ? i : i + 1;
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result[j].codewords[iOffset] = rawCodewords[rawCodewordsOffset++];
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}
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}
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return result;
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}
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int getNumDataCodewords() {
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return numDataCodewords;
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}
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byte[] getCodewords() {
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return codewords;
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}
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}
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