Tutorials:SWORD 103 - Revision history

David Haslam: /* The anatomy of an SWFilter */ Category:Tutorials

2012-08-10T12:23:30Z

‎The anatomy of an SWFilter: Category:Tutorials

Refdoc: /* The anatomy of an SWFilter */

2010-12-03T19:35:19Z

‎The anatomy of an SWFilter

David Haslam: Copied from email, lightly edited

2010-12-03T16:52:05Z

Copied from email, lightly edited

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== The anatomy of an SWFilter ==
<pre>
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...
</pre>
http://crosswire.org/svn/sword/trunk/include/swfilter.h
<pre>
... 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...
</pre>
Stay tuned for "The Red Pill" coming soon to a listserv near you.

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@@ Line 1: / Line 1: @@
 == The anatomy of an SWFilter ==
-<pre>
 At the most basic level, a SWORD filter performs some distinct and
 concise transformation to the data stream.
@@ Line 6: / Line 6: @@
 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
-<pre>
 ... there is simply 1 method you need to implemented to create a filter:
-char SWFilter::processText(
+<pre>char SWFilter::processText(
                  SWBuf &text,
          const SWKey *key = 0,
          const SWModule *module = 0) = 0;
+</pre>
 Basically, you're sent a buffer of text, possibly along with some
@@ Line 27: / Line 26: @@
 into tiny manageable chunks that anyone can tackle.
-"Handle <title> tags in a buffer?  Sure, I can do that!  That's easy....
+"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
@@ Line 36: / Line 34: @@
 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...
-</pre>
 Stay tuned for "The Red Pill" coming soon to a listserv near you.