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From: d88-jwa@byse.nada.kth.se (Jon W{tte)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Is there a defacto standard for 'drop ins'?
Message-ID: <D88-JWA.91Mar24213927@byse.nada.kth.se>
Date: 24 Mar 91 20:39:31 GMT
References: <1CE00001.aolmdnz@tbomb.ice.com> <13094@adobe.UUCP>
Sender: news@nada.kth.se (Mr News)
Organization: Royal Institute of Technology, Stockholm, Sweden
Lines: 48
In-reply-to: hawley@adobe.COM's message of 22 Mar 91 18:14:17 GMT

In article <13094@adobe.UUCP> hawley@adobe.COM (Steve Hawley) writes:

   typedef struct {
   /* stream operations.  These would probably follow Pascal calling
	conventions */
	   boolean (*EndOfStreamFunc)();
	   char (*GetCharFunc)();
	   OSErr (*PutCharFunc)();
	   OSErr (*UngetCharFunc)();
	   /* maybe Seek, and Length too */
   } StreamOps, *StreamOpsPtr;

You would rather want to get blocks at a time - like,

typedef struct {
	long		amountToRead ;
	long		flags ; /* bit 0 == SetPosition supported &c */
	pascal OSErr	( * ReadBlock ) ( char * , long ) ;
	pascal OSErr	( * PeekBlock ) ( char * , long ) ;
	pascal OSErr	( * WriteBlock ) ( char * , long ) ;
	pascal OSErr	( * SetPosition ) ( char * , long ) ;
	pascal OSErr	( * TellUser ) ( char * ) ;
} filterParam ;

pascal OSErr
MyFilterFunc ( filterParam * p , char * userData )
{
}

Or should it be handle-based ? Maybe bit 1 == Handles instead of
pointers ? Who should be responsible for allocating memory ? Should
operations in site be allowed ? (more flags :-)

userData could be filter-dependent, like "awk" command lines, or
it could be app-dependent.

More ideas ! Maybe the Net is strong enough to actually support
a de-facto standard. But we'd have to talk a few major players
into using this standard.

Happy hacking,

						h+@nada.kth.se
						Jon W{tte
--
"The IM-IV file manager chapter documents zillions of calls, all of which
seem to do almost the same thing and none of which seem to do what I want
them to do."  --  Juri Munkki in comp.sys.mac.programmer