final cog

Despite having coded in c++ for a several years, I looked at this and thought ?!?. It turns out that this is an obscure, but perfectly valid c++ construct, an initialisation list.

// TCP digest calculation
 
TCPDigest::TCPDigest (DigestAlgorithm *alg_to_use, SigKey &key):
        counter(0),
        alg (alg_to_use ? alg_to_use->clone( key ):
                          new HMAC_MD5_Algorithm (key)),
        key (key)
        // here request signatre should be taken to digest
{
}

It's primary purpose is to allow the developer to choose which superclass constructors would be called, and with what parameters (especially in the case of multiple inheritance). The initialisation list can also assign values to member variables, by using pseudo functions having the same name as the member variables. i.e. the above code assigns a value of 0 to counter.

The driving force in using an initialisation list in this source was that it is a valid way of initialising class members which are references, rather than normal variables. (In this case 'key' is declared foo &key; in the header).)