Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!ames!oliveb!sun!gorodish!guy
From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.unix.wizards
Subject: Re: UNIX Facilities for Interpreters
Message-ID: <20776@sun.uucp>
Date: Tue, 9-Jun-87 19:43:16 EDT
Article-I.D.: sun.20776
Posted: Tue Jun  9 19:43:16 1987
Date-Received: Fri, 12-Jun-87 05:21:19 EDT
References: <540@iscuva.ISCS.COM>
Sender: news@sun.uucp
Lines: 22

>    vread -- read from a file into memory [but not really, maybe].

Wow, *deja vu*.  Check out the manual page VREAD(2V) in the 4.1BSD
manuals.  Same name, same calling sequence, and, I believe, pretty
much the same semantics.

However, the manual page also says it "is likely to be replaced by
more general virtual memory facilities in the near future."  They
were, presumably, referring to the 4.2BSD "mmap" system call;
however, "mmap" wasn't really implemented for 4.2BSD.

Some systems *do* implement a real live "mmap" that permits you to
map files into your address space.  This is probably the way to go;
yes, it means you have to use different code on systems that support
"mmap" and systems that don't, but you may very well want to do so
*anyway* for performance reasons.  (Sometimes the appropriate layer
to put portable interfaces in isn't the system call layer or the
system library layer; it may be better to put it at a low layer in
the application.)
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com