/* decode_openpicc - decode the ISO14443 data gathered by OpenPICC
 *
 * (C) 2006 by Milosch Meriac <meriac@openpcd.de>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <stdlib.h>
#include <stdio.h>

#define PAUSE_MINIMUM_COUNT 32

typedef enum
{ MILLER_X = 0, MILLER_Y, MILLER_Z } TMillerState;

int counter, byte, parity, crc;
TMillerState MillerStatePrev;

void
Error (const char *message)
{
  printf ("ERROR: %s\n", message);
  exit (1);
}

void
ProcessBit (int bit, int edges)
{
  printf ("[%02i]%i ", edges, bit);

  if (counter < 8)
    {
      byte = (byte >> 1) | (bit << 7);
      if (bit)
	parity++;
    }
  else
    putchar ((((~parity) & 1) == bit) ? ' ' : '!');

  if (++counter == 9)
    {
      counter = 0;
      printf (" ==0x%02X\n", byte);

      byte = (byte ^ crc) & 0xFF;
      byte = (byte ^ byte << 4) & 0xFF;
      crc = ((crc >> 8) ^ (byte << 8) ^ (byte << 3) ^ (byte >> 4)) & 0xFFFF;

//        printf(" [%04X]\n",crc);

      byte = 0;
      parity = 0;
    }
}

void
ProcessEdges (int Edges)
{
  int bit;

  if (Edges > PAUSE_MINIMUM_COUNT)
    {
      if (!crc)
	printf ("CRC OK");
      putchar ('\n');
      counter = 0;
      byte = 0;
      parity = 0;
      crc = 0x6363;
      MillerStatePrev = MILLER_Y;
    }
  else
    {
      putchar ('X' + (char) MillerStatePrev);

      switch (MillerStatePrev)
	{
	case MILLER_X:
	  if (Edges < 10)
	    bit = 1;
	  else if (Edges > 12)
	    {
	      ProcessBit (0, 0);
	      putchar (' ');
	      bit = 1;
	    }
	  else
	    {
	      MillerStatePrev = MILLER_Z;
	      bit = 0;
	    }
	  break;
	case MILLER_Y:
	  putchar ('\n');
	  if (Edges < 10)
	    {
	      MillerStatePrev = MILLER_Z;
	      bit = -1;
	    }
	  else
	    {
	      MillerStatePrev = MILLER_X;
	      bit = 1;
	    }
	  break;
	case MILLER_Z:
	  if (Edges < 10)
	    bit = 0;
	  else if (Edges > 12)
	    {
	      printf ("[encoding error]");
	      bit = -1;
	    }
	  else
	    {
	      ProcessBit (0, 0);
	      putchar (' ');
	      MillerStatePrev = MILLER_X;
	      bit = 1;
	    }
	  break;
	}

      if (bit >= 0)
	ProcessBit (bit, Edges);
    }
}

int
main (int argc, char *argv[])
{
  int d, i, bit, bitprev, zeros;
  FILE *f;

  if (argc != 2)
    Error ("command line is 'decode datafile.bin'\n");

  if ((f = fopen (argv[1], "rb")) == NULL)
    Error ("can't open data file");

  crc = 1;
  bitprev = zeros = 0;
  while ((d = fgetc (f)) != EOF)
    {

      for (i = 0; i < 8; i++)
	{
	  bit = d & 1;
	  d >>= 1;

	  // find raising edge
	  if (bit && (bit != bitprev))
	    {
	      ProcessEdges (zeros ? zeros : PAUSE_MINIMUM_COUNT + 1);
	      zeros = 0;
	    }
	  else
	    zeros++;

	  bitprev = bit;
	}
    }
  fclose (f);

  printf ("\n\n");

  return 0;
}