Help converting a function to Qt

I would like to use encryption from the openssl library to encrypt saved user passwords

So create a function that takes the user's password as a QString and returns the encrypted version I can save with QSettings, and then reverse it to load the password and use it to login on the server.

I have an example function full implementation details can be found at
http://tldp.org/LDP/LGNET/87/vinayak.html

Code:

int encrypt (int infd, int outfd)
{
	unsigned char outbuf[OP_SIZE];
	int olen, tlen, n;
	char inbuff[IP_SIZE];
	EVP_CIPHER_CTX ctx;
	EVP_CIPHER_CTX_init (& ctx);
	EVP_EncryptInit (& ctx, EVP_bf_cbc (), key, iv);
 
	for (;;)
	  {
		  bzero (& inbuff, IP_SIZE);
 
		  if ((n = read (infd, inbuff, IP_SIZE)) == -1)
		    {
			    perror ("read error");
			    break;
		    }
		  else if (n == 0)
			  break;
 
		  if (EVP_EncryptUpdate (& ctx, outbuf, & olen, inbuff, n) != 1)
		    {
			    printf ("error in encrypt update\n");
			    return 0;
		    }
 
		  if (EVP_EncryptFinal (& ctx, outbuf + olen, & tlen) != 1)
		    {
			    printf ("error in encrypt final\n");
			    return 0;
		    }
		  olen += tlen;
		  if ((n = write (outfd, outbuf, olen)) == -1)
			  perror ("write error");
	  }
	EVP_CIPHER_CTX_cleanup (& ctx);
	return 1;
}

which I am trying to make Qt compatible

Code:

QString Encrypter::encrypt(const QString& s)
{
	QString result;
	bool processing = true;
	bool success = true;
 
	QBuffer source;
	source.setData(s.toUtf8());
	QBuffer final;
 
	unsigned char outbuff[OP_SIZE];
	int olen, tlen;
	unsigned char inbuff[IP_SIZE];
 
	quint64 chunkSize = IP_SIZE;
	quint64 readSize;
 
	EVP_CIPHER_CTX ctx;
	EVP_CIPHER_CTX_init (&ctx);
	EVP_EncryptInit (&ctx, EVP_bf_cbc (), key, iv);
 
	while(processing)
	{
		//zero out input buffer
		for(int i = 0; i < IP_SIZE; i++)
		{
			inbuff[i] = 0;
		}
 
		//populate input buffer with first chunk
		readSize = source.read((char*)inbuff, chunkSize);
 
		if(readSize == 0)
		{
			processing = false;
		}
 
		if(readSize == -1)
		{
			qDebug() << "encrypt read error";
			success = false;
			processing = false;
			break;
		}
 
		if(processing)
		{
			if (EVP_EncryptUpdate (&ctx, outbuff, &olen, inbuff, readSize) != 1)
			{
				printf ("error in encrypt update\n");
				success = false;
				processing = false;
			}
			else
			{
				if (EVP_EncryptFinal (&ctx, outbuff + olen, &tlen) != 1)
				{
					printf ("error in encrypt final\n");
					success = false;
					processing = false;
				}
			}
 
			olen += tlen;
 
			readSize = final.write((char*)outbuff, olen);
			if( readSize == -1 )
			{
				perror ("write error");
				success = false;
				processing = false;
			}
		}
	}
	EVP_CIPHER_CTX_cleanup (&ctx);
 
	if(success)
	{
		result = QString(final.data());
	}
 
	//The encrypted string
	return result;
}

But my function is failing right away with "encrypt read error". I know my solution isn't the most elegant but I was just hoping to get it working and then clean it up. I have a feeling problems are being caused by all of the different type conversions.

Help would be appreciated