Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdcad!ames!killer!elg
From: elg@killer.UUCP (Eric Green)
Newsgroups: comp.sys.amiga
Subject: Re: GaaaK! Unix networking called "GOOD"?!?
Message-ID: <4072@killer.UUCP>
Date: 13 May 88 06:38:02 GMT
References: <538@viscous>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 52

in article <538@viscous>, brianm@sco.COM (Brian Moffet) says:
> However, the ability to handle fork() and a common set of 
> InterProcess Communications between child and parent
> process would help greatly. 

Done. There is a "spawn" command in AmigaDos, which can spawn an independent
process (I don't have my manuals here at home, so I can't tell you the exact
format -- it's part of the grody BCPL crud, unless you do a LoadSeg and set up
a lightweight task at the Exec level, instead). Before you spawn, do a
CreatePort("math.myport",0); Your brand new task then does a
FindPort("math.myport"); and then sits in a loop, the first instruction of
which is a WaitPort(portpointer) which puts the process to sleep until there's
a message coming in. Have yourself two kinds of messages:  a transaction
message, and a cleanup message. The transaction message basically has a flag
saying "do it!" and a bundle of parameters. Your spawned task does a GetMsg,
does its duty, then does a ReplyMsg with the answer. When finished, just send
a quit, wait for the reply, unallocate all memory and signals associated with
the port, and go on to whatever. 

(NOTE AGAIN: I DO NOT HAVE MY MANUALS WITH ME. THE ABOVE IS A SIMPLIFICATION
OFF THE TOP OF MY HEAD, BASED UPON A WHOLE TWO WEEKS OF AMIGA PROGRAMMING
EXPERIENCE).  

> An easy way to handle this is to have your parent program
> write and compile a secondary program in the back ground while
> asking the user for parameters.  Once the secondary program
> is compiled (found out by wait()), do a fork and dup() to
> force the child process to talk via a pipe to the parent
> process.  The parent can then give the child a set of
> paramters to the equation, and the child responds with the 
> answer.  Very simple, but with a lot of overhead.

Functionally equivalent to the Amiga stuff mentioned above, except it may take
some AmigaDOS munging to figure a way of finding when the compiler is finished
doing it's exec()'ed chores. Maybe something to do with write locks and not
being able to read a file that has a write lock upon it? Keep trying to get a
read lock until you can do it?  ARGH! BCPL! BPTR'S! KILLKILLKILL!

> Oh well, sorry for rambling, I thought I would give an example
> of what I have done under Unix but not been able to do under
> the amiga.

Oh well. Keep on trying. It takes awhile. One thing I'd suggest is reading the
appropriate sections of the documentation thoroughly, while referencing a
third-party manual and the "include" files and the autodocs. The Amiga is an
amazingly open-ended machine -- it's possible to do almost anything, with a
little effort and a decent understanding of what's going on.

--
    Eric Lee Green                     {cuae2,ihnp4}!killer!elg
         Snail Mail P.O. Box 92191 Lafayette, LA 70509              
"Is a dream a lie that don't come true, or is it something worse?"