Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!CS.BROWN.EDU!jb
From: jb@CS.BROWN.EDU
Newsgroups: comp.sys.encore
Subject: Re: File buffers
Message-ID: <8808031913.AA06146@tracy.cs.brown.edu>
Date: 3 Aug 88 19:13:16 GMT
References: <585@cmx.npac.syr.edu>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 17

I'm not exactly sure how things are behaving, but I'd guess that the
problem is that while the buffer was shared, the file pointer was
not shared.

To fix this problem, after you do the fopen(), copy the entire file
pointer (FILE  *) into a new copy in a block of shared memory.  Set
the buffer by patching the copied structure to be in shared memory
as well.  (Copying after the setbuf call would probably work as well.)
Use this new file pointer instead of the one returned by fopen for
all subsequent i/o.  Don't forget that this is a shared data
structure and that mutual exclusion is needed around calls to fprintf
and fscanf (or any other routines in stdio).

This hack should work, but is totally nonstandard.  It assumes some
knowledge of how stdio works and is outside what is docummented.  Use
at your own risk.

				Jim