NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/comp/lang/pop/180

Internet Message Format | 1993-01-01 | 1.6 KB

From: [e-mail] (Steve Knight)
Date: Fri, 1 Jan 1993 17:46:32 GMT
Subject: Re: When the (Gibson) cat's away across the atlantic....
Message-ID: <[e-mail]>
Organization: Hewlett-Packard Laboratories, Bristol, UK.
Path: sparky!uunet!zaphod.mps.ohio-state.edu!sdd.hp.com!col.hp.com!news.dtc.hp.com!hpscit.sc.hp.com!hplextra!otter.hpl.hp.com!otter!sfk
Newsgroups: comp.lang.pop
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Lines: 23

Robin Popplestone writes:
> Needing to crunch a quarter of a million pixels in a hurry I have been
> reduced to writing 600 lines of C. How, I wondered to let C report its
> answers back to POP - these had to be line-segment records as well  as
> an 512*512 array  (something like the  Ramsay and Barrett  line-finder
> souped up) Now the array  was no problem - POP  knows how big it  will
> be, and just gives  C the array vector.  Line segments, the number  of
> which cannot be predicted, presented  a harder problem. I didn't  want
> to use a call-back to the POPLOG allocator, for various reasons.  So I
> made POP  hand C  a large  vector, which  C then  carves into  segment
> records (using a segment-key handed in as an argument) and a left-over
> vector.

While supporting Robin's request for suitable .h files to make this
kind of programming safer, I am puzzled by the need for it here.

Why not pre-allocate all the line-segment records and stick them
into a vector (null-terminated)?  This vector can then be passed to
C with impunity.  It is admittedly slightly more space consuming
and likely to take more slightly time to preallocate.  But this
seems like quite an acceptable cost to me.

Steve