NetNews Usenet Archive 1992 #30/NN_1992_30.iso/spool/comp/sys/isis/336

Text File | 1992-12-15 | 2.6 KB | 66 lines

Newsgroups: comp.sys.isis
Path: sparky!uunet!caen!batcomputer!cornell!ken
From: [e-mail] (Ken Birman)
Subject: Re: Sending a message to a single address
Message-ID: <[e-mail]>
Organization: Cornell Univ. CS Dept, Ithaca NY 14853
References: <[e-mail]>
Date: Tue, 15 Dec 1992 18:05:18 GMT
Lines: 55

In article <[e-mail]> [e-mail] (Mr J J Trevor) writes:
>Im using isis 2.2.7 and have the following problem:
>Given the following groups...
>G={a,b,c}        Group G contains addresses a b and c
>F={d}
>
>What is the most elegant way using ISIS to send a message from "d" in
>group F to a specific member of G, given that "d" has the address of
>this member? Also, this message must arrive at a specified entry point
>(this is why bcast_l("l" is unsuitable) since in Isis v.2.1 this
>delivered to entry point 0).

Actually, you have this slightly wrong.  First, the normal way would
be just to do:
    bcast(his_addr, entry, ....)
where his_entry is of type address*, for example:
    gv = pg_getview(pg_lookup("G"));
    bcast(&gv->gv_members[1], DOSOMETHING, ...);
You can use bcast_l for this but you need to set the addr_entry
values by hand:
    address list[2];
    list[0] = gv->gv_members[1];
    list[0].addr_entry = DOSOMETHING;
    list[1] = NULLADDRESS;
    bcast_l("l", list, ....);

>
>The only way I can easily see of doing this is to make "d" a client of
>G, and create a subgroup of G containing the single members address that
>"d" wants to send to. "d" then leaves G as a client and the newly
>created subgroup (of one address) is then destroyed. This seems rather
>heavyweight for a single cast.

Well, that would work, and it might actually give good performance
(subject to the comments about switching back and forth between groups
discussed in a prior posting).  But, you don't need to do anything so
elaborate.

>On a related note, is their a convienience function I have missed that
>will copy an address? For example, I may want to record the result of
>msg_getsender(msg_p) for much longer than the duration of the message or
>function.

You just need to allocate something of type address (as opposed to address*)
and copy explicitly:
    address copy;
    copy = *msg_getsender(mp);
    ....
Later, use © to refer to this copy of the address.  Be careful to
use storage that will be safe for as long as you might need a reference
to the copy...
--
Kenneth P. Birman                              E-mail:  [e-mail]
4105 Upson Hall, Dept. of Computer Science     TEL:     [phone] (office)
Cornell University Ithaca, NY 14853 (USA)      FAX:     [phone]