Wow! That REALLY did make a great difference! Encoding a file of 2MB took 50 seconds before, now it is done in 1 (ONE) second!
My Key is 8192 bytes long, is that the reason for why it so much faster for me? I don't really get how it works, but I guess I will figure it out. Thank you very much! -- Marcus -----Original Message----- From: Marcel Tschopp [mailto:[EMAIL PROTECTED] Sent: den 24 juni 2004 13:37 To: [EMAIL PROTECTED] Subject: Re: [PHP] Optimize simple file XOR code Hi Marcus Try this: function CryptFile($hash, $filename) { // The key used is generated using another function. // Since this function is only called once it has // nothing to do with the performance of this function $key = GenerateKey($hash); $keylen = strlen($key = implode('', $key)); $handle = fopen($filename, 'r'); while (!feof($handle)) { // Set the time limit or the script will time out // on large files set_time_limit(30); $data = fread($handle, 8192); for ($i = 0; $i < strlen($data); $i = $i + $keylen) { $data = substr_replace($data, substr($data, $i, $keylen) ^ $key, $i, $keylen); } // Return the encrypted version to the browser echo $data; } } It should return the same results, but at my machine it is about 30 percent faster. Cheers Marcel > Hi! > > I'm using a very simple algorithm to encrypt files sent from the > server "On Demand". The algorithm uses XOR for the encryption. My > problem is that the code is very slow, it can only process about 40 KB > per second on my system, so my question is, is there any more speed > optimized way to write this code? > > Here is my function: > > function CryptFile($hash, $filename) > { > // The current position in the key generated below > $key_pos = 0; > > // The key used is generated using another function. > // Since this function is only called once it has > // nothing to do with the performance of this function > $key = GenerateKey($hash); > > $handle=fopen($filename, "r"); > while (!feof($handle)) > { > // Set the time limit or the script will time out > // on large files > set_time_limit(30); > > $data = fread($handle,8192); > for ($i=0; $i<strlen($data); $i++) > { > // Change the data read from the file by using > // XOR with the key > $data[$i] = $data[$i] ^ $key[$key_pos]; > > // Calculate the next position in the key > $key_pos=($key_pos+1) % count($key); > } > > // Return the encrypted version to the browser > echo $data; > } > } > > My guess is that if one should start optimizing the code anywhere, it > would be within the for-loop. Any ideas? > > Thanks in advance! > > Regards, > Marcus > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
