Question

I want to use memcpy within class template. So my template will be limited to any link to C POD (structure) and char* (and ofcourse structures can be declared in other independent classes). I want any class to be able to subscribe its function (if it has respectful input args) to cast event. So my class now looks like:

class IGraphElement{
    typedef void FuncCharPtr(char*, int) ;
public:
    void Add(FuncCharPtr* f)
    {
        FuncVec.push_back(f);
    }
    void CastData(char * data, int length){
        for(size_t i = 0 ; i < FuncVec.size(); i++){
            char* dataCopy = new char[length];
            memcpy(dataCopy, data, length);
            FuncVec[i](dataCopy, length);
        }
    }
private:
    vector<FuncCharPtr*> FuncVec ;
};

generally I want 2 things that are really one (I try to explain in pseudocode):

template < typename GraphElementDatataStructurePtrType>
class IGraphElement{
    typedef void FuncCharPtr(GraphElementDatataStructurePtrType, int) ;  // here I want FuncCharPtr to be  of type (AnyClassThatWantsToConnectToThisGraphElement::*)(GraphElementDatataStructurePtrType, int) 

public:
    void Add(FuncCharPtr* f)
    {
        FuncVec.push_back(f);
    }

    void CastData(GraphElementDatataStructurePtrType data, int length){
        for(size_t i = 0 ; i < FuncVec.size(); i++){
            GraphElementDatataStructurePtrType dataCopy = new GraphElementDatataStructurePtrType[length];
            memcpy(dataCopy, data, length);
            FuncVec[i](dataCopy, length);
        }
    }

private:
    vector<FuncCharPtr*> FuncVec ; 
  };

Is what I desire any how possible and how to implement it into my class? (sorry – I am a c++ nube=()

Answer 1

Your problem has been addressed by the boost::signals library.
If you are interested in the inner workings you can try to implement something similar using the boost::function and boost::bind libraries.
You can research the Modern C++ Design for details about the inner workings of functor templates, or just google&ask this forum.

Here’s a solution code sketch using boost:

void DataCastHelper (boost::funtion funcCharPtr, char * data, int length) {
   char* dataCopy = new char[length];
   memcpy(dataCopy, data, length);

   funcCharPtr(dataCopy, length);
}

class IGraphElement {
public:
    void Add (FuncCharPt* f) {
        funcVec.connect(boost::bind(&DataCastHelper, f, _1, _2));
    }
    void CastData(char * data, int length){
        funcVec(data. length);
    }

private:
    boost::signal<FuncCharPtr> funcVec;
}

The FuncCharPt* f argument passed to the IGraphElement::Add method is stacked with DataCastHelper to make a data coping for you. The signal handles functors iteration and invocation and also passing arguments to functors.

Regards