Path: utzoo!attcan!uunet!snorkelwacker!apple!mips!sgi!shinobu!odin!andru
From: andru@sgi.com (Andrew Myers)
Newsgroups: comp.sys.sgi
Subject: Re: Problems with Event Queue
Keywords: qtest v. qread, push operation
Message-ID: <8888@odin.corp.sgi.com>
Date: 13 Jun 90 17:20:53 GMT
References: <14653@thorin.cs.unc.edu>
Sender: news@odin.corp.sgi.com
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 45

In article <14653@thorin.cs.unc.edu> surles@robinett.cs.unc.edu (Mark Surles) writes:
>Is there any way to get both the event type and the value
>without dequeueing the event?  Or, can I read the event and then
>somehow put it back at the FRONT of the queue?
>Mark Surles
>surles@cs.unc.edu

You could implement a wrapper around qtest/qread, whose implementation
would depend on how deep a pushback you needed. If you only need one
level, something like this should suffice:

#include "gl.h"
#include "assert.h"

long q_dev;
short q_data;
int q_hasdata;

long my_qtest()
{
    if (q_hasdata) return q_dev;
    else return qtest();
}

long my_qread(short *data)
{
    if (q_hasdata) {
	*data = q_data;
	return q_dev;
    } else {
	return qread(data);
    }
}

void my_qunread(long dev, short data)
{
    assert(!q_hasdata); /* one level pushback requirement */
    assert(dev != 0);   /* dev==0 wouldn't make sense */
    q_dev = dev;
    q_data = data;
}


-----
Andrew