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From: Gabor Kovesdan <gabor@FreeBSD.org>
Date: Mon, 22 Aug 2011 11:22:13 +0000 (UTC)
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Subject: svn commit: r225077 - user/gabor/tre-integration/contrib/tre/lib
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Author: gabor
Date: Mon Aug 22 11:22:13 2011
New Revision: 225077
URL: http://svn.freebsd.org/changeset/base/225077

Log:
  - Add a general comment

Modified:
  user/gabor/tre-integration/contrib/tre/lib/tre-heuristic.c

Modified: user/gabor/tre-integration/contrib/tre/lib/tre-heuristic.c
==============================================================================
--- user/gabor/tre-integration/contrib/tre/lib/tre-heuristic.c	Mon Aug 22 11:18:47 2011	(r225076)
+++ user/gabor/tre-integration/contrib/tre/lib/tre-heuristic.c	Mon Aug 22 11:22:13 2011	(r225077)
@@ -40,6 +40,21 @@
 #include "xmalloc.h"
 
 /*
+ * A full regex implementation requires a finite state automaton
+ * and using an automaton is always about a trade-off. A DFA is
+ * fast but complex and requires more memory because of the
+ * high number of states. NFA is slower but simpler and uses less
+ * memory. Regular expression matching is an underlying common task
+ * that is required to be efficient but correctness, clean and
+ * maintanable code are also requirements. So what we do is using
+ * an NFA implementation and heuristically locate the possible matches
+ * with a cheaper algorithm and only apply the heavy one to the
+ * possibly matching segments. This allows us to benefit from the
+ * advantages of an NFA implementation reducing the effect of the
+ * performance impact.
+ */
+
+/*
  * Parses bracket expression seeking to the end of the enclosed text.
  * The parameters are the opening (oe) and closing elements (ce).
  * Can handle nested bracket expressions.