clean up example

openssl/src/rsa.rs

@@ -23,10 +23,9 @@
 //!
 //! fn main() {
 //!     let rsa = Rsa::generate(2048).unwrap();
-//!     let data: Vec<u8> = String::from("foobar").into_bytes();
-//!     let mut encrypted_data: Vec<u8>  = vec![0; 512];
-//!     let padding = Padding::PKCS1;
-//!     let _ = rsa.public_encrypt(&data, encrypted_data.as_mut_slice(), padding).unwrap();
+//!     let data = b"foobar";
+//!     let mut buf = vec![0; rsa.size() as usize];
+//!     let encrypted_len = rsa.public_encrypt(data, &mut buf, Padding::PKCS1).unwrap();
 //! }
 //! ```
 use ffi;