[3.1.0] Make StringHash system-agnostic.

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1621 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/StringHash.php

@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * This is in almost every respect equivalent to an array except
+ * that it keeps track of which keys were accessed.
+ *
+ * @warning For the sake of backwards compatibility with early versions
+ *     of PHP 5, you must not use the $hash[$key] syntax; if you do
+ *     our version of offsetGet is never called.
+ */
+class HTMLPurifier_StringHash extends ArrayObject
+{
+    protected $accessed = array();
+    
+    /**
+     * Retrieves a value, and logs the access.
+     */
+    public function offsetGet($index) {
+        $this->accessed[$index] = true;
+        return parent::offsetGet($index);
+    }
+    
+    /**
+     * Returns a lookup array of all array indexes that have been accessed.
+     * @return Array in form array($index => true).
+     */
+    public function getAccessed() {
+        return $this->accessed;
+    }
+    
+    /**
+     * Resets the access array.
+     */
+    public function resetAccessed() {
+        $this->accessed = array();
+    }
+}