Re: Geeting hash_map values back

From:

Bernd Strieder <strieder@informatik.uni-kl.de>

Newsgroups:

comp.lang.c++

Date:

Tue, 22 Jan 2008 12:11:36 +0100

Message-ID:

<fn4j0n$q7f$1@news.uni-kl.de>

Hello,

C C++ C++ wrote:

I have thread create function like this
pthread_create(&ThreadA,NULL,threadWork::requestThread,(void
*)&ResultSet); // <--- ResultSet is hasp_map with around 10 key-values
in it.

in threadWork.cc member function is defined
void * threadWork::requestThread(void *ResultSet)
{
cout << typeid(ResultSet).name() << ResultSet<<endl; // <<------ its
printing void * which is correct, how can i get my hash_map and its
values back ?

You get it back by casting the void pointer to the right type, then you
can use all member functions of the hash_map. Perhaps you read in a C++
textbooks on the C++ casts, what advantages they have compared to your
C style cast used here. If there are more than one possibility of
classes of objects passed, then you have to use some variant data type,
or create your own wrapper class.

std::hash_set<int> * hsp = (std::hash_set<int> *)ResultSet;
if (hsp->size() > 0) std::cout<<"First:"<<*hsp->begin();

}

In your case I would recommend using a descriptive class of your own,
like WorkThreadData. This way all the casting will have to be done
once, and the actual types like your hash_set, which are pretty nasty
to handle with casts are behind a clean interface.

Bernd Strieder