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Date: Mon, 14 Sep 2015 13:03:34 +0200 (CEST)
From: Roland Lutz <rlutz AT hedmen DOT org>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] shortest way towards parsing .pcb files outside
 pcb
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On Sat, 12 Sep 2015, DJ Delorie wrote:
> Scripts wouldn't *need* to use pcb's parser, they could use any old
> parser library, since the scripts already know what the parts of the
> schema they're interested in look like.  Read file, fiddle with the
> parts you know, write file leaving everything else intact.

That's easier said than done.  With an XML file, you have basically no 
choice but to use an existing parser library; the format is just too 
complex (and XML parser bugs are a popular exploit vector).  But these 
parsers aren't designed to tell you which parts of the file are which so 
you would know what to change.  You could, of course, write the parsed 
data back into an XML, but to do that without losing information, you 
would again need context information about the file format which you want 
to avoid in the first place.  For example, you would need to know in which 
parts of the file whitespace is significant so you can add or remove tags 
while still keeping the file human-readable.  And there are XML processing 
instructions, CDATA sections, and so on…

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