Utility Function of the Day

There hasn't been a utility function of the day for a long time around here, so this one is extra special.
The following method calculates a digest for a DOM hierarchy including attribute values and text content. The special part about it is that it ignores ordering of elements and attributes and disregards comments completely.

The Code:

/**

 * Recursively calculate DOM digest, 

 * disregarding order but taking all content except

 * comments into consideration.

 * @param node The node to start with

 */

public static long digestDOM(Node node)

{

	long digest = 0L;



	/**

	 * First calculate the 'self' digest

	 */

	if (node instanceof Attr)

	{

		Attr attr = (Attr) node;



		digest = attr.getName().hashCode() + attr.getValue().hashCode();

	}

	else if (node instanceof Text)

	{

		Text text = (Text) node;



		digest = XMLUtils.getContent(text).hashCode();

	}

	else if (node instanceof Element)

	{

		Element element = (Element) node;



		digest = element.getTagName().hashCode();

	}



	/**

	 * Now calculate the attribute's digest, disregarding order

	 */

	long attributeDigest = 0L;



	NamedNodeMap attributes = node.getAttributes();



	if (attributes != null)

	{

		/**

		 * Iterate through a node list, examine only elements

		 */

		int attributeCount = attributes.getLength();



		for (int i = 0; i < attributeCount; i++)

		{

			Node currentNode = attributes.item(i);



			attributeDigest += digestDOM(currentNode);

		}

	}



	/**

	 * Append the attribute digest

	 */

	digest = (digest * 2 + (attributeDigest));



	/**

	 * Then calculate the children, disregarding ordering

	 */

	long childrenDigest = 0L;



	/**

	 * Iterate through a node list, examine only elements

	 */



	NodeList childNodes = node.getChildNodes();



	int nodeCount = childNodes.getLength();



	for (int i = 0; i < nodeCount; i++)

	{

		Node currentNode = childNodes.item(i);



		childrenDigest += digestDOM(currentNode);

	}



	/**

	 * Append the children digest

	 */

	digest = (digest * 4 + (childrenDigest));



	return digest;

}

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Enjoy!