callback.cpp

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C++ 代码 · 共 80 行

/****************************************************************************
*
*                            Open Watcom Project
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*    This file contains Original Code and/or Modifications of Original
*    Code as defined in and that are subject to the Sybase Open Watcom
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#include <iostream.h>

// SYSTEM provides a hook before it prints "hello"

struct CALLBACK {
    virtual void hook( void * ) = 0;
};

struct SYSTEM {
    void doit( void )
    {
        _call_back_object->hook( _call_back_data );
        cout << "hello" << endl;
    }
    void register_call_back( CALLBACK *cb, void *data )
    {
        _call_back_object = cb;
        _call_back_data = data;
    }
private:
    CALLBACK *_call_back_object;
    void *_call_back_data;
};

// user of SYSTEM callback

struct use_BASE {
};

struct use_CALLBACK : use_BASE, CALLBACK {
    void hook( void *p )
    {
        unsigned *q = (unsigned *) p;

        cout << "call back called with " << *q << endl;
    }
};

SYSTEM zz;

main()
{
    unsigned x = 5;

    zz.register_call_back( new use_CALLBACK, &x );
    zz.doit();
}