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/*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.zxing.qrcode.decoder;
/**
* <p>Encapsulates a block of data within a QR Code. QR Codes may split their data into
* multiple blocks, each of which is a unit of data and error-correction codewords. Each
* is represented by an instance of this class.</p>
*
* @author Sean Owen
*/
final class DataBlock {
private final int numDataCodewords;
private final byte[] codewords;
private DataBlock(int numDataCodewords, byte[] codewords) {
this.numDataCodewords = numDataCodewords;
this.codewords = codewords;
}
/**
* <p>When QR Codes use multiple data blocks, they are actually interleaved.
* That is, the first byte of data block 1 to n is written, then the second bytes, and so on. This
* method will separate the data into original blocks.</p>
*
* @param rawCodewords bytes as read directly from the QR Code
* @param version version of the QR Code
* @param ecLevel error-correction level of the QR Code
* @return DataBlocks containing original bytes, "de-interleaved" from representation in the
* QR Code
*/
static DataBlock[] getDataBlocks(byte[] rawCodewords,
Version version,
ErrorCorrectionLevel ecLevel) {
if (rawCodewords.length != version.getTotalCodewords()) {
throw new IllegalArgumentException();
}
// Figure out the number and size of data blocks used by this version and
// error correction level
Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);
// First count the total number of data blocks
int totalBlocks = 0;
Version.ECB[] ecBlockArray = ecBlocks.getECBlocks();
for (int i = 0; i < ecBlockArray.length; i++) {
totalBlocks += ecBlockArray[i].getCount();
}
// Now establish DataBlocks of the appropriate size and number of data codewords
DataBlock[] result = new DataBlock[totalBlocks];
int numResultBlocks = 0;
for (int j = 0; j < ecBlockArray.length; j++) {
Version.ECB ecBlock = ecBlockArray[j];
for (int i = 0; i < ecBlock.getCount(); i++) {
int numDataCodewords = ecBlock.getDataCodewords();
int numBlockCodewords = ecBlocks.getECCodewordsPerBlock() + numDataCodewords;
result[numResultBlocks++] = new DataBlock(numDataCodewords, new byte[numBlockCodewords]);
}
}
// 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.
int shorterBlocksTotalCodewords = result[0].codewords.length;
int longerBlocksStartAt = result.length - 1;
while (longerBlocksStartAt >= 0) {
int numCodewords = result[longerBlocksStartAt].codewords.length;
if (numCodewords == shorterBlocksTotalCodewords) {
break;
}
longerBlocksStartAt--;
}
longerBlocksStartAt++;
int shorterBlocksNumDataCodewords = shorterBlocksTotalCodewords - ecBlocks.getECCodewordsPerBlock();
// The last elements of result may be 1 element longer;
// first fill out as many elements as all of them have
int rawCodewordsOffset = 0;
for (int i = 0; i < shorterBlocksNumDataCodewords; i++) {
for (int j = 0; j < numResultBlocks; j++) {
result[j].codewords[i] = rawCodewords[rawCodewordsOffset++];
}
}
// Fill out the last data block in the longer ones
for (int j = longerBlocksStartAt; j < numResultBlocks; j++) {
result[j].codewords[shorterBlocksNumDataCodewords] = rawCodewords[rawCodewordsOffset++];
}
// Now add in error correction blocks
int max = result[0].codewords.length;
for (int i = shorterBlocksNumDataCodewords; i < max; i++) {
for (int j = 0; j < numResultBlocks; j++) {
int iOffset = j < longerBlocksStartAt ? i : i + 1;
result[j].codewords[iOffset] = rawCodewords[rawCodewordsOffset++];
}
}
return result;
}
int getNumDataCodewords() {
return numDataCodewords;
}
byte[] getCodewords() {
return codewords;
}
}
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