function _openssl_ofb_process($plaintext, &$encryptIV, &$buffer)
    {
        if (strlen($buffer['xor'])) {
            $ciphertext = $plaintext ^ $buffer['xor'];
            $buffer['xor'] = substr($buffer['xor'], strlen($ciphertext));
            $plaintext = substr($plaintext, strlen($ciphertext));
        } else {
            $ciphertext = '';
        }

        $block_size = $this->block_size;

        $len = strlen($plaintext);
        $key = $this->key;
        $overflow = $len % $block_size;

        if (strlen($plaintext)) {
            if ($overflow) {
                $ciphertext.= openssl_encrypt(substr($plaintext, 0, -$overflow) . str_repeat("\0", $block_size), $this->cipher_name_openssl, $key, $this->openssl_options, $encryptIV);
                $xor = $this->_string_pop($ciphertext, $block_size);
                if ($this->continuousBuffer) {
                    $encryptIV = $xor;
                }
                $ciphertext.= $this->_string_shift($xor, $overflow) ^ substr($plaintext, -$overflow);
                if ($this->continuousBuffer) {
                    $buffer['xor'] = $xor;
                }
            } else {
                $ciphertext = openssl_encrypt($plaintext, $this->cipher_name_openssl, $key, $this->openssl_options, $encryptIV);
                if ($this->continuousBuffer) {
                    $encryptIV = substr($ciphertext, -$block_size) ^ substr($plaintext, -$block_size);
                }
            }
        }

        return $ciphertext;
    }