// XPath 式中の接頭辞のない名前テストに接頭辞 prefix を追加する
// e.g. '//body[@class = "foo"]/p' -> '//prefix:body[@class = "foo"]/prefix:p'
// http://nanto.asablo.jp/blog/2008/12/11/4003371
function addDefaultPrefix(xpath, prefix) {
	var tokenPattern = /([A-Za-z_\u00c0-\ufffd][\w\-.\u00b7-\ufffd]*|\*)\s*(::?|\()?|(".*?"|'.*?'|\d+(?:\.\d*)?|\.(?:\.|\d+)?|[\)\]])|(\/\/?|!=|[<>]=?|[\(\[|,=+-])|([@$])/g;
	var TERM = 1, OPERATOR = 2, MODIFIER = 3;
	var tokenType = OPERATOR;
	prefix += ':';
	function replacer(token, identifier, suffix, term, operator, modifier) {
		if (suffix) {
			tokenType = 
				(suffix == ':' || (suffix == '::' && (identifier == 'attribute' || identifier == 'namespace')))
				? MODIFIER : OPERATOR;
		} else if (identifier) {
			if (tokenType == OPERATOR && identifier != '*')
				token = prefix + token;
			tokenType = (tokenType == TERM) ? OPERATOR : TERM;
		} else {
			tokenType = term ? TERM : operator ? OPERATOR : MODIFIER;
		}
		return token;
	}
	return xpath.replace(tokenPattern, replacer);
}