Copy example to module level

//! High level interface to certain symmetric ciphers.

//!

//! # Examples

//!

//! Encrypt data in AES128 CBC mode

//!

//! ```

//! use openssl::symm::{encrypt, Cipher};

//!

//! let cipher = Cipher::aes_128_cbc();

//! let data = b"Some Crypto Text";

//! let key = b"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F";

//! let iv = b"\x00\x01\x02\x03\x04\x05\x06\x07\x00\x01\x02\x03\x04\x05\x06\x07";

//! let ciphertext = encrypt(

//!     cipher,

//!     key,

//!     Some(iv),

//!     data).unwrap();

//!

//! assert_eq!(

//!     b"\xB4\xB9\xE7\x30\xD6\xD6\xF7\xDE\x77\x3F\x1C\xFF\xB3\x3E\x44\x5A\x91\xD7\x27\x62\x87\x4D\

//!       \xFB\x3C\x5E\xC4\x59\x72\x4A\xF4\x7C\xA1",

//!     &ciphertext[..]);

//! ```

use std::cmp;

use std::ptr;

use libc::c_int;