linux下HMAC函数

#include <stdlib.h>
#include <openssl/evp.h>
#include <openssl/md5.h>
#include <openssl/hmac.h>

#include"string.h"

#include <openssl/hmac.h>

 unsigned char *HMAC(const EVP_MD *evp_md, const void *key,               int key_len, const unsigned char *d, int n,               unsigned char *md, unsigned int *md_len);

HMAC(EVP_md5(),key,key_len, d, n, md, md_len
);