doFinal method

@override int doFinal(Uint8List inp, int inpOff, Uint8List out, int outOff,)

Process the last block of data given by inp and starting at offset inpOff and pad it as explained in this interface's description.

For encryption, the resulting cipher text is put in out beginning at position outOff and the method returns the total bytes put in out, including the padding. Note that, if inp length is equal to the cipher's block size, out will need to be twice the cipher's block size to allow place for the padding.

For decryption, the resulting plain text is put in out beginning at position outOff and the method returns the total bytes put in out, excluding the padding. Note that the method may return 0 if the last block was all padding.

Implementation

@override
int doFinal(Uint8List inp, int inpOff, Uint8List out, int outOff) {
  if (_encrypting!) {
    var lastInputBlock = Uint8List(blockSize)..setAll(0, inp.sublist(inpOff));

    var remainder = inp.length - inpOff;

    if (remainder < blockSize) {
      // Padding goes embedded in last block of data
      padding.addPadding(lastInputBlock, inp.length - inpOff);

      processBlock(lastInputBlock, 0, out, outOff);

      return blockSize;
    } else {
      // Padding goes alone in an additional block
      processBlock(inp, inpOff, out, outOff);

      padding.addPadding(lastInputBlock, 0);

      processBlock(lastInputBlock, 0, out, outOff + blockSize);

      return 2 * blockSize;
    }
  } else {
    // Decrypt last block and remove padding
    processBlock(inp, inpOff, out, outOff);

    var padCount = padding.padCount(out.sublist(outOff));

    var padOffsetInBlock = blockSize - padCount;

    out.fillRange(outOff + padOffsetInBlock, out.length, 0);

    return padOffsetInBlock;
  }
}