openssl加密

我想讨论一下openssl的读写方法。
假设我的数据结构如下:

/-----------------------------------------------------\
|  my_header   |  PAYLOAD                             |
\-----------------------------------------------------/
       |                              |
      \ /                            \ /
 not encrypted                      encrypted

I think the proper algorithm would be like this :
   SEND:
   build my_header with my own header.
   encrypt PAYLOAD with encryption function
   attach my_header and PAYLOAD (encrypted) to one buffer
   send it using common POSIX function just like send or sendto
   RECV:
   using common POSIX function just like recv or recvfrom.
   extract my_header and PAYLOAD(encrypted)
   decrypt PAYLOAD with decryption function
   at last i got my_header and PAYLOAD(decrypted).

如果你面临上述问题,你的方法如何。因为openssl对发送到SSL_write function(CMIIW)的所有数据进行加密。

谢谢

也许,一个恰当的问题是,在openssl中,可以用来加密/解密有效负载的加密和解密函数是什么?。