Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!uwm.edu!bionet!agate!usenet.ins.cwru.edu!ncoast!allbery
From: allbery@NCoast.ORG (Brandon S. Allbery KB8JRR/AA)
Newsgroups: comp.lang.perl
Subject: Re: anyone gotten mmap to work w/ perl?
Message-ID: <1991Apr17.235656.10193@NCoast.ORG>
Date: 17 Apr 91 23:56:56 GMT
References: <1991Apr9.051702.22978@jpl-devvax.jpl.nasa.gov> <28046072.4CFC@tct.com> <129281@uunet.UU.NET>
Reply-To: allbery@ncoast.ORG (Brandon S. Allbery KB8JRR/AA)
Followup-To: comp.lang.perl
Organization: North Coast Public Access Un*x (ncoast)
Lines: 32

As quoted from <129281@uunet.UU.NET> by rbj@uunet.UU.NET (Root Boy Jim):
+---------------
| In article <28046072.4CFC@tct.com> chip@tct.com (Chip Salzenberg) writes:
| >According to lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall):
| >>What you'd really kinda like is a way to mmap a particular variable, and
| >>let Perl worry about it when it gets reallocated...
| >
| >If such a thing were done, we we would get shmat() for System V IPC
| >almost for free.
| 
| As it should be. I have already complained that shm{read,write}
| detach the shared memory segment between accesses. The implementor
| wrote back and said he did it that way just to get it to work, but
| didn't really understand how to do what Larry suggested.
+---------------

Were I designing it, I'd arrange for strings (well, symbol table entries) to
contain the "allocate" and "extend" function pointers for the strings.  That
way, you can do a whole bunch of things:  extending strings enlarges the
mmap() or shmat() area, or calls a function which arranges for a usersub to
know what's going on (e.g. changes the projection list information for the
Oracle usersubs recently posted), etc.  (I'd mention "fixed-size" strings, but
I can only think of one valid use for them:  mmap()/shmat().  If there were a
way to map device driver registers into user-mode code, this would also be a
good application.)

++Brandon
-- 
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