懂PHP且懂点C的大神进去

void hdth_normal_decode(char * outstr,char * instr)
{
	int   i=0;
	int j = 0;
	int len = strlen(instr);
	for(i=0;i	{   
		int   h=(instr[i]-'c');   
		int   l=(instr[i+1]-'f');   
		char  c=(l<<4)+(h&0xf);   
		outstr[j]=c;
		j++;
	}   

	return;
}

原文：www.comunits.net
密文：jmjmjmqhflrlplhmqlllgmfmqhqlhlgm

function hdth_normal_decode($in) {
  $out = ''; 
  $len = strlen($in);
  for($i=0; $i<$len; $i+=2) {
    $h = ord($in{$i}) - ord('c');
    $l = ord($in{$i+1}) - ord('f');
    $c = ($l << 4) + ($h & 0xf);
    $out .= chr($c);
  }
  return $out;
}

function hdth_normal_encode($in) {
  $out = '';
  $len = strlen($in);
  for($i=0; $i<$len; $i++) {
    $c = ord($in{$i});
    $l = ($c >> 4) + ord('f');
    $h = ($c & 0xf) + ord('c');
    $out .= chr($h) . chr($l);
  }
  return $out;
}

echo hdth_normal_encode('www.comunits.net');