/*
 * Software License Agreement (BSD License)
 *
 * Copyright (c) 2010, Roel Verdult
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the
 * names of its contributors may be used to endorse or promote products
 * derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <stdio.h>
#include <stdint.h>

#define BLOCK_COUNT 7
#define BLOCK_LENGTH 4
#define BLOCK_TOTAL (BLOCK_COUNT*BLOCK_LENGTH)

typedef unsigned char byte_t;

int main(int argc, char *argv[])
{
  FILE* pf;
  byte_t buf[BLOCK_TOTAL];
  uint32_t crc = 0;
  uint32_t block;
  
  // Check for required arguments
  if (argc < 2)
  {
    printf("syntax: lpcrc <firmware.bin>\n");
    return 1;
  }
  
  // Try to open the supplied firmware
  if ((pf = fopen(argv[1],"rb+")) == NULL)
  {
    printf("error: could not open file [%s] with write access\n",argv[1]);
    return 1;
  }

  // Read out the data blocks used for crc calculation
  if (fread(buf,1,BLOCK_TOTAL,pf) != BLOCK_TOTAL)
  {
    printf("error: could not read required bytes\n");
    fclose(pf);
    return 1;
  }

  // Compute the crc value
  for (block=0; block<BLOCK_COUNT; block++)
  {
    crc += *((uint32_t*)(buf+(block*BLOCK_LENGTH)));
  }
  crc = (~crc) + 1;
  
  // Reposition the file stream indicator to switch between read and write
  if (fseek(pf,0,SEEK_CUR) != 0)
  {
    printf("error: could not switch from read to write mode\n");
    fclose(pf);
    return 1;
  }
  
  // Write the crc back to the file
  if (fwrite((byte_t*)&crc,1,BLOCK_LENGTH,pf) != BLOCK_LENGTH)
  {
    printf("error: could not write crc back to file\n");
    fclose(pf);
    return 1;
  }

  printf("succesfully updated crc to: %08x\n",crc);
  fclose(pf);
  
  return 0;
}