/* IP creator (makeip)
 *
 * Copyright (C) 2000, 2001, 2002, 2019, 2020 The KOS Team and contributors.
 * All rights reserved.
 *
 * This code was contributed to KallistiOS (KOS) by Andress Antonio Barajas
 * (BBHoodsta). It was originally made by Marcus Comstedt (zeldin). Some
 * portions of code were made by Andrew Kieschnick (ADK/Napalm). Heavily
 * updated by SiZiOUS. Bootstrap replacement (IP.TMPL) was made by Jacob
 * Alberty (LiENUS).
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 HOLDER OR CONTRIBUTORS 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 "crc.h"

int
calc_crc(const unsigned char *buf, int size)
{
  int i, c, n = 0xffff;
  for (i = 0; i < size; i++) {
    n ^= (buf[i]<<8);
    for (c = 0; c < 8; c++) {
      if (n & INITIAL_PROGRAM_SIZE)
        n = (n << 1) ^ 4129;
      else
        n = (n << 1);
    }
  }

  return n & 0xffff;
}

void
update_crc(char *ip)
{
  int n = calc_crc((unsigned char *)(ip+0x40), 16);
  char buf[5];

  sprintf(buf, "%04X", n);
  if(memcmp(buf, ip+0x20, 4)) {
    memcpy(ip+0x20, buf, 4);
  }
}
