Generic implementation of property-lists.

Signed-off-by: Edward Z. Yang <edwardzyang@thewritingpot.com>

library/HTMLPurifier/PropertyList.php

@@ -0,0 +1,72 @@
+<?php
+
+/**
+ * Generic property list implementation
+ */
+class HTMLPurifier_PropertyList
+{
+    /**
+     * Internal data-structure for properties
+     */
+    protected $data = array();
+
+    /**
+     * Parent plist
+     */
+    protected $parent;
+
+    /**
+     * Recursively retrieves the value for a key
+     */
+    public function get($name) {
+        if ($this->has($name)) return $this->data[$name];
+        if ($this->parent) return $this->parent->get($name);
+        throw new HTMLPurifier_Exception("Key '$name' not found");
+    }
+
+    /**
+     * Sets the value of a key, for this plist
+     */
+    public function set($name, $value) {
+        $this->data[$name] = $value;
+    }
+
+    /**
+     * Returns true if a given key exists
+     */
+    public function has($name) {
+        return array_key_exists($name, $this->data);
+    }
+
+    /**
+     * Resets a value to the value of it's parent, usually the default. If
+     * no value is specified, the entire plist is reset.
+     */
+    public function reset($name = null) {
+        if ($name == null) $this->data = array();
+        else unset($this->data[$name]);
+    }
+
+    /**
+     * Returns an iterator for traversing this array, optionally filtering
+     * for a certain prefix.
+     */
+    public function getIterator($filter = null) {
+        $a = new ArrayObject($this->data);
+        return new HTMLPurifier_PropertyListIterator($a->getIterator(), $filter);
+    }
+
+    /**
+     * Returns the parent plist.
+     */
+    public function getParent() {
+        return $this->parent;
+    }
+
+    /**
+     * Sets the parent plist.
+     */
+    public function setParent($plist) {
+        $this->parent = $plist;
+    }
+}