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+IPSet
+=====
+
+IPSet is a PHP library for matching IP addresses against a set of CIDR
+specifications.
+
+Here is how you use it:
+
+<pre lang="php">
+// At startup, calculate the optimized data structure for the set:
+$ipset = new IPSet( array(
+    '208.80.154.0/26',
+    '2620:0:861:1::/64',
+    '10.64.0.0/22',
+) );
+
+// Runtime check against cached set (returns bool):
+if ( $ipset->match( $ip ) ) {
+    // ...
+}
+</pre>
+
+In rough benchmarking, this takes about 80% more time than `in_array()` checks
+on a short (a couple hundred at most) array of addresses.  It's fast either way
+at those levels, though, and IPSet would scale better than in_array if the
+array were much larger.
+
+For mixed-family CIDR sets, however, this code gives well over 100x speedup vs
+iterating `IP::isInRange()` over an array of CIDR specs.
+
+The basic implementation is two separate binary trees (IPv4 and IPv6) as nested
+php arrays with keys named 0 and 1.  The values false and true are terminal
+match-fail and match-success, otherwise the value is a deeper node in the tree.
+
+A simple depth-compression scheme is also implemented: whole-byte tree
+compression at whole-byte boundaries only, where no branching occurs during
+that whole byte of depth.  A compressed node has keys 'comp' (the byte to
+compare) and 'next' (the next node to recurse into if 'comp' matched successfully).
+
+For example, given these inputs:
+
+<pre>
+25.0.0.0/9
+25.192.0.0/10
+</pre>
+
+The v4 tree would look like:
+
+<pre lang="php">
+root4 => array(
+    'comp' => 25,
+    'next' => array(
+        0 => true,
+        1 => array(
+            0 => false,
+            1 => true,
+        ),
+    ),
+);
+</pre>
+
+(multi-byte compression nodes were attempted as well, but were
+a net loss in my test scenarios due to additional match complexity)
+
+
+License
+-------
+Copyright 2014, 2015 Brandon Black <blblack@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+<http://www.gnu.org/copyleft/gpl.html>