zxing/csharp/qrcode/decoder/DataBlock.cs

/*
* 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.
*/

using System;
namespace com.google.zxing.qrcode.decoder
{

    /// <summary> <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>
    /// 
    /// </summary>
    /// <author>  srowen@google.com (Sean Owen)
    /// </author>
    public sealed class DataBlock
    {
        internal int NumDataCodewords
        {
            get
            {
                return numDataCodewords;
            }

        }
        internal sbyte[] Codewords
        {
            get
            {
                return codewords;
            }

        }

        //UPGRADE_NOTE: Final was removed from the declaration of 'numDataCodewords '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
        private int numDataCodewords;
        //UPGRADE_NOTE: Final was removed from the declaration of 'codewords '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
        private sbyte[] codewords;

        public DataBlock(int numDataCodewords, sbyte[] codewords)
        {
            this.numDataCodewords = numDataCodewords;
            this.codewords = codewords;
        }

        /// <summary> <p>When QR Codes use multiple data blocks, they are 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>
        /// 
        /// </summary>
        /// <param name="rawCodewords">bytes as read directly from the QR Code
        /// </param>
        /// <param name="version">version of the QR Code
        /// </param>
        /// <param name="ecLevel">error-correction level of the QR Code
        /// </param>
        /// <returns> {@link DataBlock}s containing original bytes, "de-interleaved" from representation in the
        /// QR Code
        /// </returns>
        internal static DataBlock[] getDataBlocks(sbyte[] rawCodewords, Version version, ErrorCorrectionLevel ecLevel)
        {
            // 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.getTotalECCodewords() + numDataCodewords;
                    result[numResultBlocks++] = new DataBlock(numDataCodewords, new sbyte[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;
                }
                if (numCodewords != shorterBlocksTotalCodewords + 1)
                {
                    throw new System.SystemException("Data block sizes differ by more than 1");
                }
                longerBlocksStartAt--;
            }
            longerBlocksStartAt++;

            int shorterBlocksNumDataCodewords = shorterBlocksTotalCodewords - ecBlocks.getTotalECCodewords();
            // 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++];
                }
            }

            if (rawCodewordsOffset != rawCodewords.Length)
            {
                throw new System.SystemException();
            }

            return result;
        }
    }
}