Review

18

com/itextpdf/text/pdf/qrcode/Encoder.java

interleaveWithECBytes(BitVector, int, int, int, BitVector)

class Encoder {
  /**
   * Interleave "bits" with corresponding error correction bytes. On success, store the result in
   * "result". The interleave rule is complicated. See 8.6 of JISX0510:2004 (p.37) for details.
   */
  static void interleaveWithECBytes(BitVector bits, int numTotalBytes,
      int numDataBytes, int numRSBlocks, BitVector result) throws WriterException {

    // "bits" must have "getNumDataBytes" bytes of data.
    if (bits.sizeInBytes() != numDataBytes) {
      throw new WriterException("Number of bits and data bytes does not match");
    }

    // Step 1.  Divide data bytes into blocks and generate error correction bytes for them. We'll
    // store the divided data bytes blocks and error correction bytes blocks into "blocks".
    int dataBytesOffset = 0;
    int maxNumDataBytes = 0;
    int maxNumEcBytes = 0;

    // Since, we know the number of reedsolmon blocks, we can initialize the vector with the number.
    ArrayList<BlockPair> blocks = new ArrayList<BlockPair>(numRSBlocks);

    for (int i = 0; i < numRSBlocks; ++i) {
      int[] numDataBytesInBlock = new int[1];
      int[] numEcBytesInBlock = new int[1];
      getNumDataBytesAndNumECBytesForBlockID(
          numTotalBytes, numDataBytes, numRSBlocks, i,
          numDataBytesInBlock, numEcBytesInBlock);

      ByteArray dataBytes = new ByteArray();
      dataBytes.set(bits.getArray(), dataBytesOffset, numDataBytesInBlock[0]);
      ByteArray ecBytes = generateECBytes(dataBytes, numEcBytesInBlock[0]);
      blocks.add(new BlockPair(dataBytes, ecBytes));

      maxNumDataBytes = Math.max(maxNumDataBytes, dataBytes.size());
      maxNumEcBytes = Math.max(maxNumEcBytes, ecBytes.size());
      dataBytesOffset += numDataBytesInBlock[0];
    }
    if (numDataBytes != dataBytesOffset) {
      throw new WriterException("Data bytes does not match offset");
    }

    // First, place data blocks.
    for (int i = 0; i < maxNumDataBytes; ++i) {
      for (int j = 0; j < blocks.size(); ++j) {
        ByteArray dataBytes = blocks.get(j).getDataBytes();
        if (i < dataBytes.size()) {
          result.appendBits(dataBytes.at(i), 8);
        }
      }
    }
    // Then, place error correction blocks.
    for (int i = 0; i < maxNumEcBytes; ++i) {
      for (int j = 0; j < blocks.size(); ++j) {
        ByteArray ecBytes = blocks.get(j).getErrorCorrectionBytes();
        if (i < ecBytes.size()) {
          result.appendBits(ecBytes.at(i), 8);
        }
      }
    }
    if (numTotalBytes != result.sizeInBytes()) {  // Should be same.
      throw new WriterException("Interleaving error: " + numTotalBytes + " and " +
          result.sizeInBytes() + " differ.");
    }
  }

}