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From: newbery@rata.vuw.ac.nz (Michael Newbery)
Newsgroups: comp.sys.mac.programmer
Subject: Re: RAM serial driver and event handling
Message-ID: <1990Oct19.043030.27980@comp.vuw.ac.nz>
Date: 19 Oct 90 04:30:30 GMT
References: <1990Sep20.143626.23475@midway.uchicago.edu> <10326@goofy.Apple.COM> <1990Sep24.000818.29952@svc.portal.com> <10749@goofy.Apple.COM>
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In article <10749@goofy.Apple.COM> han@Apple.COM (Byron Han, scapegoat) writes:
>In article <1990Sep24.000818.29952@svc.portal.com> leonardr@svc.portal.com writes:
>>	How would you recommed that you check for 'already open'?  I can't
>
>You might want to check the driver unit table and check the driver flags
>to see if the driver has already been opened... there is a routine in the
>7.0 version of the Comm Rsrc Mgr called CRMIsDriverOpen() which does this...
And the following code (in Pascal) does the job now

CONST
	{ refNums of .AIn etc }
	rAIn		= -6;
	rAOut		= -7;
	rBIn		= -8;
	rBOut		= -9;

IF 
BTst(BOr(GetDCtlEntry(rAIn)^^.dCtlFlags,GetDCtlEntry(rAOut)^^.dCtlFlags),5)
THEN
{ The A driver(s) are open }

Reference: IM II-190 "The Device Manager---The Structure of a Device Driver"

--
Michael Newbery<newbery@rata.vuw.ac.nz>
Nunc est bibendum
   Horace Od I xxxvii 1