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From: beard@ux5.lbl.gov (Patrick C Beard)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Multiple Inheritance for HandleObjects in C++
Message-ID: <6182@helios.ee.lbl.gov>
Date: 16 Jul 90 15:24:09 GMT
References: <15132@reed.UUCP> <268BA8DC.4CD4@intercon.com> <37@hite386.UUCP>
Sender: usenet@helios.ee.lbl.gov
Reply-To: beard@ux5.lbl.gov (Patrick C Beard)
Organization: Berkeley Systems, Inc.
Lines: 42
X-Local-Date: 16 Jul 90 08:24:09 PDT


Here is how I use Handles and C++ objects together without fragmenting
heaps.  This allows full C++ style objects with single and multiple
inheritance.  

// overloaded storage operators.  Allows floating C++ objects.
void* operator new(size_t size) 
{
  Handle h = NewHandleClear((long)size);
  if(!h || MemError() != noErr)
	return nil;
  MoveHHi(h);
  return (void*)*h;
}

operator delete(void* p)
{
  if(p) {
    Handle h = RecoverHandle((Ptr)p);
    DisposHandle(h);
  }
}


Using these storage operators, create an object like so:

MyClass **h_instance, *p_instance;

p_instance = new MyClass;
h_instance = RecoverHandle((Ptr)p_instance);

Now, you can refer to the object henceforth using h_instance, which you
can cast to a handle and perform standard locking and unlocking before
and after use.  For example:

(**h_instance).MyMethod(); //  be sure to lock if necessary!

--
-------------------------------------------------------------------------------
-  Patrick Beard, Macintosh Programmer                        (beard@lbl.gov) -
-  Berkeley Systems, Inc.  ".......<dead air>.......Good day!" - Paul Harvey  -
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