/******************************************************************************
** Functions by Derrick Sobodash
** http://www.cinnamonpirate.com/
** Submitted to ROM Hacking.net on July 3, 2006
******************************************************************************/

/******************************************************************************
** apply_ips()
*******************************************************************************
** syntax: void apply_ips(string ips_file, string bin_file)
*******************************************************************************
** Applies ips_file to bin_file if both files exist. Compatable with
** IPS RLE and LunarIPS CUT command.
******************************************************************************/

function apply_ips($ips_file, $bin_file)
{

  // Make sure the input is all valid
  if(!file_exists($ips_file))
    die("Error: apply_ips(): Unable to open $ips_file\n\n");
  if(!file_exists($bin_file))
    die("Error: apply_ips(): Unable to open $bin_file\n\n");

  // Open the patch file as a stream
  $ips = fopen($ips_file, "rb");

  if(fread($ips, 5) != "PATCH")
    die("Error: apply_ips(): Supplied IPS file does not appear to be an IPS format patch\n\n");

  // Open the binary file in read/write mode
  $fa = fopen($bin_file, "r+b");

  // str("EOF") signals the end of an IPS patch
  $temp = fread($ips, 3);

  while($temp != "EOF")
  {

    // Seek to the specified offset in the binary
    fseek($fa, punpack($temp, "b"), SEEK_SET);
    $length = punpack(fread($ips, 2), "b");

    // 0x0 signals an IPS RLE byte

    if($length==0)
    {

      // RLE can be up to 0xffff chars long
      $rle_length = punpack(fread($ips, 2), "b");

      // Character to repeat follows length
      $rle_char = fgetc($ips);

      // Loop the length of the RLE, writing the byte each time
      for($rle_count = 0; $rle_count < $rle_length; $rle_count ++)
        fputs($fa, $rle_char);

    }

    else
      fputs($fa, fread($ips, $length));

    // Read the next offset
    $temp = fread($ips, 3);

  }

  // FuSoYa's LunarIPS program writes beyond EOF to support a "cut" command
  // The offset after EOF is where the file is to be cut at
  if(ftell($ips) < filesize($ips_file))
    ftruncate($fa, punpack(fread($ips, 3), "b"));

  fclose($fa);
  fclose($ips);

}


/******************************************************************************
** create_ips()
*******************************************************************************
** syntax: void create_ips(string source_file, string modified_file[,
**         string ips_file])
*******************************************************************************
** Creates an IPS file by comparing the source file and modified file and
** writes the output to ips_file. If ips_file is not specified,
** modified_file + ".ips" will be used. Compatable with IPS RLE and the
** LunarIPS CUT command.
******************************************************************************/

function create_ips($source_file, $modified_file, $ips_file = null)
{

  // Set a default IPS filename if none was specified
  if($ips_file == null)
    $ips_file = $modified_file . ".ips";

  // Make sure the input is all valid
  if(!file_exists($source_file))
    die("Error: create_ips(): Unable to open $source_file\n\n");
  if(!file_exists($modified_file))
    die("Error: create_ips(): Unable to open $modified_file\n\n");

  // Open the files for comparing
  $src = fopen($source_file, "rb");
  $mod = fopen($modified_file, "rb");

  $patch = "PATCH";

  if(filesize($modified_file) < filesize($source_file))
    $end_at = filesize($modified_file);
  else
    $end_at = filesize($source_file);

  while(ftell($mod) < $end_at - 1)
  {

    $src_char = fgetc($src);
    $mod_char = fgetc($mod);
    $bytes = "";
    $rle_time = 0;

    if($src_char != $mod_char)
    {

      $patch .= ppack(ftell($mod) - 1, 24, "b");

      while($src_char != $mod_char && ftell($mod) != $end_at + 1)
      {

        if(strlen($bytes) > 4 && punpack(substr($bytes, -4, 4) ^ (substr($bytes, -4, 1).substr($bytes, -4, 1).substr($bytes, -4, 1).substr($bytes, -4, 1)), "b") == 0)
        {

          $rle_time = 1;
          $bytes = substr($bytes, 0, -4);

          fseek($mod, ftell($mod) - 5);
          fseek($src, ftell($mod));

          $rle_off = ftell($mod);
          $rle_char = fgetc($mod);
          $rle_len = 0;

          while($mod_char == $rle_char && $rle_len < 0xffff)
          {

            $rle_len ++;
            $mod_char = fgetc($mod);

          }

          fseek($mod, ftell($mod) - 1);
          fseek($src, ftell($mod));

          break 1; // Exit the while()

        }

        $bytes .= $mod_char;
        $src_char = fgetc($src);
        $mod_char = fgetc($mod);

      }

      $patch .= ppack(strlen($bytes), 16, "b") . $bytes;

      if($rle_time == 1)
      {

        $patch .= ppack($rle_off, 24, "b") . ppack(0, 16, "b") . ppack($rle_len, 16, "b") . $rle_char;
        $rle_time = 0;

      }

      else
      {

        fseek($src, ftell($src)-1, SEEK_SET);
        fseek($mod, ftell($mod)-1, SEEK_SET);

      }

    }

  }


  if(filesize($modified_file) > $end_at)
  {

    fseek($mod, $end_at, SEEK_SET);

    while(ftell($mod) < filesize($modified_file) - 1)
    {

      $mod_char = fgetc($mod);
      $bytes = $mod_char;

      $patch .= ppack(ftell($mod) - 1, 24, "b");

      while(ftell($mod) < filesize($modified_file) && strlen($bytes) < 0xffff)
      {

        if(strlen($bytes) > 4 && punpack(substr($bytes, -4, 4) ^ (substr($bytes, -4, 1).substr($bytes, -4, 1).substr($bytes, -4, 1).substr($bytes, -4, 1)), "b") == 0)
        {

          $rle_time = 1;
          $bytes = substr($bytes, 0, -4);
          fseek($mod, ftell($mod) - 4);

          $rle_off = ftell($mod);
          $rle_char = fgetc($mod);
          $rle_len = 0;

          while($mod_char == $rle_char && $rle_len < 0xffff)
          {

            $rle_len ++;
            $mod_char = fgetc($mod);

          }

          fseek($mod, ftell($mod) - 1);

          break 1; // Exit the while()

        }

        $mod_char = fgetc($mod);
        $bytes .= $mod_char;

      }

      $patch .= ppack(strlen($bytes), 16, "b") . $bytes;

      if($rle_time == 1)
      {

        $patch .= ppack($rle_off, 24, "b") . ppack(0, 16, "b") . ppack($rle_len, 16, "b") . $rle_char;
        $rle_time = 0;

      }

    }

    $patch .= "EOF";

  }

  else if(filesize($modified_file) == filesize($source_file))
    $patch .= "EOF";

  else
    $patch .= "EOF" . ppack(filesize($modified_file), 24, "b");

  fclose($mod);
  fclose($src);

  $fo = fopen($ips_file, "w");
  fputs($fo, $patch);
  fclose($fo);

}