Callbacks in C++
manual polymorphism
//----------------------------------------
// l i b r a r y c o d e
//----------------------------------------
#include <string.h> //for memcpy, memcmp
class CallbackData
{
public:
typedef void (CallbackData::*PMEMFUNC)();
CallbackData(const void* pClient_, const void* ppMemfunc_):
_pClient(pClient_)
{memcpy(_ppMemfunc,ppMemfunc_,sizeof(PMEMFUNC));}
const void* pClient() const {return _pClient;}
const void* ppMemfunc() const {return _ppMemfunc;}
private:
char _ppMemfunc[sizeof(PMEMFUNC)];
const void* _pClient;
};
//----------------------------------------
template <class P1>
class Callback1Base
{
public:
void operator()(P1 p1_) const
{_thunk(_data, p1_);}
protected:
typedef void (*THUNK)(const CallbackData&, P1);
Callback1Base(THUNK thunk_, const void* pClient_, const void* ppMemfunc_):
_thunk(thunk_),
_data(pClient_,ppMemfunc_)
{}
private:
CallbackData _data;
THUNK _thunk;
};
//----------------------------------------
template <class P1, class Client, class PMemfunc>
class Callback1:
public Callback1Base<P1>
{
public:
Callback1(Client& client_, PMemfunc pMemfunc_):
Callback1Base<P1>(thunk,&client_,&pMemfunc_)
{}
private:
static void thunk(const CallbackData& data_, P1 parm_)
{
Client* pClient = (Client*) data_.pClient();
PMemfunc& pMemfunc = (*(PMemfunc*)(data_.ppMemfunc()));
(pClient->*pMemfunc)(parm_);
}
};
//----------------------------------------
template <class P1, class Client, class TRT, class CallType, class TP1>
inline Callback1<P1,Client,TRT(CallType::*)(TP1)>
make_callback(Callback1Base<P1>*,
Client& client_,
TRT (CallType::* const& memFunc_)(TP1))
{
typedef TRT (CallType::*PMEMFUNC)(TP1);
return Callback1<P1,Client,PMEMFUNC>(client_, memFunc_);
}
//----------------------------------------
template <class P1, class Client, class TRT, class CallType, class TP1>
inline Callback1<P1,Client,TRT(CallType::*)(TP1)const>
make_callback(Callback1Base<P1>*,
Client& client_,
TRT (CallType::* const& memFunc_)(TP1) const)
{
typedef TRT (CallType::*PMEMFUNC)(TP1) const;
return Callback1<P1,Callee,PMEMFUNC>(client_, memFunc_);
}
//----------------------------------------
class Button
{
public:
Button(const Callback1Base<Button*>& callback_):
_callback(callback_)
{}
void push() {_callback(this);}
private:
const Callback1Base<Button*> _callback;
};
//----------------------------------------
// c l i e n t c o d e
//----------------------------------------
#include <iostream.h>
class CdPlayer
{
public:
void playButtonPushed(Button*) {cout << "PLAY" << endl;}
void stopButtonPushed(Button*) {cout << "STOP" << endl;}
};
//----------------------------------------
main()
{
CdPlayer aCdPlayer;
Button playButton
(
make_callback
((Callback1Base<Button*>*)0, aCdPlayer, &CdPlayer::playButtonPushed)
);
Button stopButton
(
make_callback
((Callback1Base<Button*>*)0, aCdPlayer, &CdPlayer::stopButtonPushed)
);
playButton.push();
stopButton.push();
return 0;
};
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Callbacks in C++
Copyright © 1996-2000 Paul Jakubik
Created: 26 July 1996. Last update: 26 November 2000.
pauljakubik@yahoo.com