[sword-devel] Why You Should Love SWORD 103 - What Is A Filters

Greg Hellings greg.hellings at gmail.com
Fri Dec 3 08:52:07 MST 2010

I realize we're on #3 already, I just wanted to say "thanks" for this
set of "SWORD 10*" emails.

And I hope our Wiki Czar find the time to translate these into a nice
series of intro/tutorials that we can maintain and update as some of
us use these to dive deeper into the codebase that has supported us
for so many year now. :)


On Fri, Dec 3, 2010 at 9:19 AM, Troy A. Griffitts <scribe at crosswire.org> wrote:
> *The anatomy of an SWFilter*
> ____________________________
> At the most basic level, a SWORD filter performs some distinct and
> concise transformation to the data stream.
> The actual signature of a filter is very minimal, and looking at the
> SWFilter interface itself...
> http://crosswire.org/svn/sword/trunk/include/swfilter.h
> ... there is simply 1 method you need to implemented to create a filter:
> char SWFilter::processText(
>                SWBuf           &text,
>        const   SWKey           *key    = 0,
>        const   SWModule        *module = 0) = 0;
> Basically, you're sent a buffer of text, possibly along with some
> context in the form of an SWKey and SWModule-- in case you care, and
> then you make some small change to the buffer.
> Easy, right?  Well, sortof.
> Anyone can write a filter.  The great thing about filters is that they
> partition up a very complicated task: processing a complex document,
> into tiny manageable chunks that anyone can tackle.
> "Handle <title> tags in a buffer?  Sure, I can do that!  That's easy....
>  Wait....  What should I _DO_ with a <title> tag?"
> That's when the real world hits and things get more complex.  A SWORD
> filter is an easy to grasp, easy to code against, abstract concept.
> How filters are orchestrated together inside the SWORD engine-- what
> distinct roles they are expected to fill, when, and in what order-- is
> hidden knowledge that for years only few have been privy to yield...
> Stay tuned for "The Red Pill" coming soon to a listserv near you.
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