[gxml/xpath: 1/8] Error.vala: add get_last_error_msg convenience function NamespaceAttr.vala: make Ns accessible inter

[Richard Hans Schwarting <rschwart src gnome org>]

commit a5fee913124fb107e87dd51b82fe855c7283ea5a
Author: Adam Ples <ples adam gmail com>
Date:   Mon Oct 14 05:24:28 2013 -0400

    Error.vala: add get_last_error_msg convenience function
    NamespaceAttr.vala: make Ns accessible internally, for XPath
    Node.vala: add evaluate function for XPath

 gxml/Error.vala         |   14 ++++++++++++++
 gxml/NamespaceAttr.vala |    2 +-
 gxml/Node.vala          |   22 ++++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletions(-)
---
diff --git a/gxml/Error.vala b/gxml/Error.vala
index f0d6405..af367a8 100644
--- a/gxml/Error.vala
+++ b/gxml/Error.vala
@@ -3,6 +3,20 @@ namespace GXml {
                PARSER, WRITER;
        }
 
+       // TODO: rename
+       /**
+        * Returns error message for last registered error.
+        */
+       internal static string get_last_error_msg () {
+               Xml.Error* error = Xml.get_last_error ();
+
+               if (error == null)
+                       return "No error reported by libxml2";
+               else
+                       return libxml2_error_to_string (error);
+       }
+
+       // TODO: replace usage of this with xml_error_msg
        internal static string libxml2_error_to_string (Xml.Error *e) {
                return "%s:%s:%d: %s:%d: %s".printf (
                        e->level.to_string ().substring (8 /* skipping XML_ERR_ */),
diff --git a/gxml/NamespaceAttr.vala b/gxml/NamespaceAttr.vala
index 79b9f5a..8fe0ef9 100644
--- a/gxml/NamespaceAttr.vala
+++ b/gxml/NamespaceAttr.vala
@@ -32,7 +32,7 @@ namespace GXml {
         */
        public class NamespaceAttr : Node {
                /** Private properties */
-               private Xml.Ns *node;
+               internal Xml.Ns *node;  // XPATH:TODO: do they extend us?
 
                /** Constructors */
                internal NamespaceAttr (Xml.Ns *node, Document doc) {
diff --git a/gxml/Node.vala b/gxml/Node.vala
index 711eef1..67d2f90 100644
--- a/gxml/Node.vala
+++ b/gxml/Node.vala
@@ -492,5 +492,27 @@ namespace GXml {
                public virtual string to_string (bool format = false, int level = 0) {
                        return "Node(%d:%s)".printf (this.node_type, this.node_name);
                }
+
+               /*** XPath functions ***/
+
+               /* XPATH:TODO: should Node implement "XPathEvaluator" as an interface? No? */
+
+               /**
+                * Evaluates XPath expression in context of current DOM node (or Document).
+                *
+                * @param expr XPath expression
+                * @param nsr namespace resolver object (prefix -> URI mapping)
+                * @param res_type type to cast resulting value to
+                * @return XPath.Result object containing result type and value
+                * @throws DomError when node type is not supported as context of evaluation
+                * @throws XPath.Error when supplied with invalid XPath expression
+                */
+               public XPath.Result evaluate (string expr, XPath.NSResolver? nsr = null,
+                       XPath.ResultType res_type = XPath.ResultType.ANY)
+                       throws DomError, XPath.Error
+               {
+                       var expression = new XPath.Expression (expr, nsr);
+                       return expression.evaluate (this, res_type);
+               }
        }
 }