datablock.js

/*
  Ported to JavaScript by Lazar Laszlo 2011 
  
  lazarsoft@gmail.com, www.lazarsoft.info
  
*/

/*
*
* 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.
*/


function DataBlock(numDataCodewords,  codewords)
{
	this.numDataCodewords = numDataCodewords;
	this.codewords = codewords;
	
	this.__defineGetter__("NumDataCodewords", function()
	{
		return this.numDataCodewords;
	});
	this.__defineGetter__("Codewords", function()
	{
		return this.codewords;
	});
}	
	
DataBlock.getDataBlocks=function(rawCodewords,  version,  ecLevel)
{
	
	if (rawCodewords.length != version.TotalCodewords)
	{
		throw "ArgumentException";
	}
	
	// Figure out the number and size of data blocks used by this version and
	// error correction level
	var ecBlocks = version.getECBlocksForLevel(ecLevel);
	
	// First count the total number of data blocks
	var totalBlocks = 0;
	var ecBlockArray = ecBlocks.getECBlocks();
	for (var i = 0; i < ecBlockArray.length; i++)
	{
		totalBlocks += ecBlockArray[i].Count;
	}
	
	// Now establish DataBlocks of the appropriate size and number of data codewords
	var result = new Array(totalBlocks);
	var numResultBlocks = 0;
	for (var j = 0; j < ecBlockArray.length; j++)
	{
		var ecBlock = ecBlockArray[j];
		for (var i = 0; i < ecBlock.Count; i++)
		{
			var numDataCodewords = ecBlock.DataCodewords;
			var numBlockCodewords = ecBlocks.ECCodewordsPerBlock + numDataCodewords;
			result[numResultBlocks++] = new DataBlock(numDataCodewords, new Array(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.
	var shorterBlocksTotalCodewords = result[0].codewords.length;
	var longerBlocksStartAt = result.length - 1;
	while (longerBlocksStartAt >= 0)
	{
		var numCodewords = result[longerBlocksStartAt].codewords.length;
		if (numCodewords == shorterBlocksTotalCodewords)
		{
			break;
		}
		longerBlocksStartAt--;
	}
	longerBlocksStartAt++;
	
	var shorterBlocksNumDataCodewords = shorterBlocksTotalCodewords - ecBlocks.ECCodewordsPerBlock;
	// The last elements of result may be 1 element longer;
	// first fill out as many elements as all of them have
	var rawCodewordsOffset = 0;
	for (var i = 0; i < shorterBlocksNumDataCodewords; i++)
	{
		for (var j = 0; j < numResultBlocks; j++)
		{
			result[j].codewords[i] = rawCodewords[rawCodewordsOffset++];
		}
	}
	// Fill out the last data block in the longer ones
	for (var j = longerBlocksStartAt; j < numResultBlocks; j++)
	{
		result[j].codewords[shorterBlocksNumDataCodewords] = rawCodewords[rawCodewordsOffset++];
	}
	// Now add in error correction blocks
	var max = result[0].codewords.length;
	for (var i = shorterBlocksNumDataCodewords; i < max; i++)
	{
		for (var j = 0; j < numResultBlocks; j++)
		{
			var iOffset = j < longerBlocksStartAt?i:i + 1;
			result[j].codewords[iOffset] = rawCodewords[rawCodewordsOffset++];
		}
	}
	return result;
}