Function silc_hmac_update
SYNOPSIS
void silc_hmac_update(SilcHmac hmac, const unsigned char *data,
uint32 data_len);
DESCRIPTION
This function may be called to add data to be used in the MAC
computation. This can be called multiple times to add data from
many sources before actually performing the HMAC. Once you've
added all the data you need you can call the silc_hmac_final to
actually produce the MAC.
EXAMPLE
unsigned char mac[20];
uint32 mac_len;
silc_hmac_init(hmac);
silc_hmac_update(hmac, data, data_len);
silc_hmac_update(hmac, more_data, more_data_len);
silc_hmac_final(hmac, mac, &mac_len);