Function dtls_hmac_init 

pub unsafe extern "C" fn dtls_hmac_init(
    ctx: *mut dtls_hmac_context_t,
    key: *const c_uchar,
    klen: usize,
)

Initializes an existing HMAC context.

@param ctx The HMAC context to initialize. @param key The secret key. @param klen The length of @p key.