Function nginx::HMAC

pub unsafe extern "C" fn HMAC(
    evp_md: *const EVP_MD, 
    key: *const c_void, 
    key_len: c_int, 
    d: *const c_uchar, 
    n: size_t, 
    md: *mut c_uchar, 
    md_len: *mut c_uint
) -> *mut c_uchar