aes encryptor with rust_crypto

gistfile1.rs

fn encrypt_block(block: &[u8], key: &[u8]) -> Result<Vec<u8>, SymmetricCipherError> {
    let mut encryptor: Box<symmetriccipher::Encryptor> = aes::cbc_encryptor(
        aes::KeySize::KeySize256,
        key,
        &[0, ..16],
        PkcsPadding
    );
    
    let mut final_result = Vec::<u8>::new();
    let mut buffer = [0, ..4096];
    let mut read_buffer = buffer::RefReadBuffer::new(block);
    let mut write_buffer = buffer::RefWriteBuffer::new(&mut buffer);
    
    while !read_buffer.is_empty() {
        try!(encryptor.encrypt(&mut read_buffer, &mut write_buffer, true));        
        final_result.push_all(write_buffer.take_read_buffer().take_remaining());
    }
    
    Ok(final_result)
}