/*
* Copyright 2008 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.datamatrix.decoder;
/**
* <p>
* Encapsulates a block of data within a Data Matrix Code. Data Matrix 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 bbrown@google.com (Brian Brown)
*/
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 Data Matrix Codes use multiple data blocks, they actually interleave
* the bytes of each of them. 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 Data Matrix Code
* @param version
* version of the Data Matrix Code
* @return DataBlocks containing original bytes, "de-interleaved" from
* representation in the Data Matrix Code
*/
static DataBlock[] getDataBlocks(byte[] rawCodewords, Version version) {
// Figure out the number and size of data blocks used by this version
Version.ECBlocks ecBlocks = version.getECBlocks();
// First count the total number of data blocks
int totalBlocks = 0;
Version.ECB[] ecBlockArray = ecBlocks.getECBlocks();
for (Version.ECB ecBlock : ecBlockArray) {
totalBlocks += ecBlock.getCount();
}
// Now establish DataBlocks of the appropriate size and number of data
// codewords
DataBlock[] result = new DataBlock[totalBlocks];
int numResultBlocks = 0;
for (Version.ECB ecBlock : ecBlockArray) {
for (int i = 0; i < ecBlock.getCount(); i++) {
int numDataCodewords = ecBlock.getDataCodewords();
int numBlockCodewords = ecBlocks.getECCodewords()
+ 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 less byte. Figure out where these start.
// TODO(bbrown): There is only one case where there is a difference for
// Data Matrix for size 144
int longerBlocksTotalCodewords = result[0].codewords.length;
// int shorterBlocksTotalCodewords = longerBlocksTotalCodewords - 1;
int longerBlocksNumDataCodewords = longerBlocksTotalCodewords
- ecBlocks.getECCodewords();
int shorterBlocksNumDataCodewords = longerBlocksNumDataCodewords - 1;
// The last elements of result may be 1 element shorter for 144 matrix
// first fill out as many elements as all of them have minus 1
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
boolean specialVersion = version.getVersionNumber() == 24;
int numLongerBlocks = specialVersion ? 8 : numResultBlocks;
for (int j = 0; j < numLongerBlocks; j++) {
result[j].codewords[longerBlocksNumDataCodewords - 1] = rawCodewords[rawCodewordsOffset++];
}
// Now add in error correction blocks
int max = result[0].codewords.length;
for (int i = longerBlocksNumDataCodewords; i < max; i++) {
for (int j = 0; j < numResultBlocks; j++) {
int iOffset = specialVersion && j > 7 ? i - 1 : i;
result[j].codewords[iOffset] = rawCodewords[rawCodewordsOffset++];
}
}
if (rawCodewordsOffset != rawCodewords.length) {
throw new IllegalArgumentException();
}
return result;
}
int getNumDataCodewords() {
return numDataCodewords;
}
byte[] getCodewords() {
return codewords;
}
}