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From: keith@nih-csl.UUCP (keith gorlen)
Newsgroups: comp.lang.c++
Subject: Re: Virtual Functions in IPC environment
Message-ID: <265@nih-csl.UUCP>
Date: Wed, 2-Sep-87 18:07:26 EDT
Article-I.D.: nih-csl.265
Posted: Wed Sep  2 18:07:26 1987
Date-Received: Sat, 5-Sep-87 08:29:13 EDT
References: <1120@lznv.ATT.COM>
Organization: NIH-CSL, Bethesda, MD
Lines: 45
Summary: OOPS library storeOn()/readFrom() can be used to pass objects across process boundaries, but it may be too expensive for your application.

In article <1120@lznv.ATT.COM->, mark@lznv.ATT.COM (MARK SMITH) writes:
-> 
-> I am building a message-based system consisting of client/server processes
-> which I would like to implement using C++.  As such, for a given message
-> I would like to define the base class
-> 
-> class MsgHdr { IPC private data items; public: IPC access functions(); };
-> 
-> and a set of derived classes
-> 
-> class DerivedN: public MsgHdr {
-> 	private data for DerivedN;
-> public:
-> 	virtual void Operate();		// server: do DerivedN-specific fct
-> };
-> 
-> However, I encounter two difficulties:
-> 
-> (1) Although the intention is clearly to allow Operate() only to be
-> usable by the server, I can't find a way to disallow a client process from
-> linking with Operate.  Since I am memory-conscious (I'm using swapping UNIX), 
An easy way around this is to define a dummy version of Operate that just
issues an error message and link this with clients instead of the real Operate.

-> (2) Similarly, the client can't send a DerivedN and expect Operate to work, 
-> since the server gets a DerivedN Operate linked in the address space
-> of the client.  Memory fault core dumped.

My Object-Oriented Program Support (OOPS) class library implements a
general mechanism similar to Smalltalk's storeOn/readFrom that permits
OOPS objects to be moved across process boundaries

To get a copy of the "guru-only" version of OOPS, just send me a
letter on your company or university letterhead requesting the
"Object-Oriented Program Support (OOPS) class library for C++" and a
reel of 1/2" mag tape (a small reel will suffice).  I'll return the
tape with a copy of OOPS recorded on it in tar format at 1600 bpi, and
I'll include a copy of the (incomplete) OOPS reference manual.

Please include your uucp address in the letter.
-- 
	Keith Gorlen			phone: (301) 496-5363
	Building 12A, Room 2017		uucp: seismo!elsie!nih-csl!keith
	National Institutes of Health
	Bethesda, MD 20892