yDec.php



/* Module:  yDec
   Version: 0.9
   Date:    25.Sep.2002
   Author:  Rasmus Schultz (mindplay@mindplay.dk)
   Usage:   See included example (test.php)
   License: GPL - See http://www.gnu.org/copyleft/gpl.html
 
   PLEASE NOTE:
 
   CRC32 checks aren't implemented - I don't know how to do this.
   The crc32() function in PHP does not seem useful in this case,
   as it only allows you to calculate everything in one go - we
   don't want to do that here, since doing so would make memory
   usage unpredictable. If you figure out how to add the CRC32
   calculation, please send me the code: mindplay@mindplay.dk

   The ydecode function returns one of the following values:
 
   0 = Decode successful
   1 = Unable to open file
   2 = Unable to locate start of yencoded data
   3 = Invalid yenc header
   4 = Invalid multipart header
   5 = Unable to write file
   6 = Encoded data is broken or incomplete (size mismatch)
*/

function getyencparam($line, $name) {
  $value = NULL;
  if ($pos = strpos($line, ' '.$name.'=')) {
    $pos += 2+strlen($name);
    if ($endpos = strpos($line, ' ', $pos+1)) {
      $value = substr($line, $pos, $endpos-$pos);
    }
  }
  return($value);
}

function ydecode($filename, $folder) {
  $bufferSize = 4096;
  $buffer = str_repeat(chr(0), $bufferSize);
  $bufferLength = 0;
  $written = 0;
  if (!($fileIn = fopen($filename, 'rb'))) {
    return(1);
  }
  while ($line = fgets($fileIn, 4096)) {
    $line = rtrim($line, "\n\r");
    if (strncmp('=ybegin', $line, 7)==0) {
      break;
    }
  }
  if (feof($fileIn)) {
    return(2);
  }
  if (!($pos = strpos($line, 'name='))) {
    return(3);
  }
  $fileName = trim(substr($line, $pos+5));
  if ($partNo = getyencparam($line, 'part')) {
    $ok = FALSE;
    while ($line = fgets($fileIn, 4096)) {
      $line = rtrim($line, "\n\r");
      if (strncmp('=ypart', $line, 6)==0) {
        $ok = TRUE;
        break;
      }
    }
    if (!($ok)) {
      return(4);
    } else {
      if (!($begin = getyencparam($line, 'begin'))) {
        return(4);
      } else {
        if (file_exists($folder.$fileName)) {
          $fs = filesize($folder.$fileName);
          $fmode = 'r+b';
        } else {
          $fs = 0;
          $fmode = 'wb';
        }
        if (!($fileOut = fopen($folder.$fileName, $fmode))) {
          return(5);
        }
        if (!(fseek($fileOut, $begin-1, SEEK_SET)==0)) {
          return(5);
        }
      }
    }
  } else {
    if (!($fileOut = fopen($folder.$fileName, 'wb'))) {
      return(5);
    }
  }
  $char = 0;
  $special = FALSE;
  while ($line = fgets($fileIn, 4096)) {
    $line = rtrim($line, "\n\r");
    if (strncmp('=yend', $line, 5)==0) {
      break;
    }
    if ($line != '') {
      for ($lcv=0; $lcv < strlen($line); $lcv++) {
        $char = ord($line{$lcv});
        if ($char!=61) {
          $buffer{$bufferLength++} = chr($special?$char-106:$char-42);
          if ($bufferLength==$bufferSize) {
            if (!fwrite($fileOut, $buffer, $bufferLength)) {
              return(5);
            }
            // *** TO-DO: accumulate buffer to CRC32 sum
            $written += $bufferLength;
            $bufferLength = 0;
          }
          $special = FALSE;
        } else {
          $special = TRUE;
        }
      }
    }
  }
  if ($bufferLength>0) {
    if (!fwrite($fileOut, $buffer, $bufferLength)) {
      return(5);
    }
    // *** TO-DO: accumulate buffer to CRC32 sum
    $written += $bufferLength;
  }
  // *** TO-DO: finalize CRC32 sum
  fclose($fileOut);
  fclose($fileIn);
  if ($line != '') {
    if (strncmp('=yend', $line, 5)==0) {
      if ($size = getyencparam($line, 'size')) {
        if ($size != $written) {
          return(6);
        }
      }
      // *** TO-DO: compare finalized CRC32 sum to $pcrc32
      $pcrc32 = getyencparam($line, 'pcrc32');
    }
  }
  return(0);
}

?>




test.php

The following example should produce the file joystick.jpg

I'm decoding the two parts in reverse order, just to show that this works.

Done.