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From: ph@ssd.kodak.com (Pete Hoch)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Is there a defacto standard for 'drop ins'?
Message-ID: <1991Mar26.184520.11253@ssd.kodak.com>
Date: 26 Mar 91 18:45:20 GMT
References: <1CE00001.aolmdnz@tbomb.ice.com> <13094@adobe.UUCP>
Sender: news@ssd.kodak.com
Organization: Eastman Kodak
Lines: 44

>><1991Mar21.223638.4346@ssd.kodak.com>, ph@ssd.kodak.com (Pete Hoch) writes:
>>> So I was wondering, do they all do it the same way?  Should
>>> Apple step in and provide a filter manager?  Is this hard to
>>> do today without Apples help?  Also, is this a good idea?

>In article <1CE00001.aolmdnz@tbomb.ice.com> time@ice.com writes:
>>Most of these mechanisms use a very similar technique.
>>However, all differ in content and calling conventions, and it is

In article <13094@adobe.UUCP> hawley@adobe.UUCP (Steve Hawley) writes:
>Since Pete was interested in a general way of doing filters, why not have
>the following (off the top of my head) for byte oriented streams:

   prototypes deleted

>The idea is that the parent program passes in pointer to functions to do all
>operations one would need for a stream.  The main could then use the ops on
>the stream to transform the data as needed:

>Of course, this will not be particularly speedy because of the overhead added
>by the function calling, but you wanted generality, right?

However the overhead could be such a problem that this would not be
practical.  What I was thinking was something more allong the lines
of a call back routine that the programmer supplies to the system.

For example:
    pascal OSErr myFilter( void    *source,     // The data comes from
                           long    sSize,       // size of the data in bytes
                           long    sNext,       // offset to the next sample
                           void    *dest,       // The data goes to
                           long    dSize,       // size of the data in bytes
                           long    dNext)       // offset to the next sample

Then you need a way to select and install filters.  Perhaps the Comm ToolBox
is a good example of this and can be expanded and generalized.

Pete

-- 
Pete Hoch                                  | ..somewhere..!kodak!ph   ..or..
Color Systems ISPD. 3/65/RL		   | ph@ssd.kodak.com         ..or..
Eastman Kodak Co. 	   		   | ph@kodak.com
Rochester, NY 14650-1805                   | 716-722-????