//-----------------------------------------------------------------------------
// Function: mega_read()
// Author  : D
// Website : http://www.cinnamonpirate.com/
// Info    : Extracted from the NINJA 1.0 source code
//
// Input   : filename as string
// Output  : deinterleaved ROM binary as string
//-----------------------------------------------------------------------------

function mega_read($infile) {
  $fd = fopen($infile, "rb");
  fseek($fd, 0x100, SEEK_SET);
  if(fread($fd, 4) == "SEGA") {
    echo "File is already in BIN format ...\n";
    fseek($fd, 0, SEEK_SET);
    return(fread($fd, filesize($infile)));
  }
  fseek($fd, 0x8, SEEK_SET);
  if(bin2hex(fread($fd, 2)) == "AABB") {
    echo "File is in SMD format, converting to BIN ...\n";
    fseek($fd, 0x200, SEEK_SET);
    $num_blocks = (filesize($infile)-0x200)/(0x4000);
    $output = "";
    for($i=0; $i<$num_blocks; $i++)
      $output.= smd_deinterleave(fread($fd, 0x4000));
    return(substr($output, 0x200));
  }
  else
    die(print "ERROR: Invalid Genesis ROM!\n");
}

//-----------------------------------------------------------------------------
// Function: smd_deinterleave()
// Author  : D
// Website : http://www.cinnamonpirate.com/
// Info    : Extracted from the NINJA 1.0 source code
//
// Input   : 16KB block as string
// Output  : deinterleaved SMD block as string
//-----------------------------------------------------------------------------

function smd_deinterleave($chunk) {
  $low   = 1;
  $high  = 0;
  $block = "";
  for($i=0; $i<0x2000; $i++) {
    $block[$low] = $chunk[$i];
    $block[$high] = $chunk[(0x2000+$i)];
    $low  = $o+2;
    $high = $e+2;
  }
  return($block);
}

//-----------------------------------------------------------------------------