adding xml xpath context as an actual object

ext/nokogiri/native.c

@@ -25,6 +25,7 @@ void Init_native()
   init_xml_node();
   init_xml_text();
   init_xml_node_set();
+  init_xml_xpath_context();
   init_xml_xpath();
   init_xml_sax_parser();
   init_xml_reader();

ext/nokogiri/native.h

@@ -15,6 +15,7 @@
 #include <xml_text.h>
 #include <xml_node_set.h>
 #include <xml_xpath.h>
+#include <xml_xpath_context.h>
 #include <xml_sax_parser.h>
 #include <xml_reader.h>
 #include <html_sax_parser.h>

ext/nokogiri/xml_xpath.c

@@ -1,8 +1,13 @@
 #include <xml_xpath.h>
 
-static void free_xpath_object(xmlXPathObjectPtr xpath)
+static void deallocate(xmlXPathObjectPtr xpath)
 {
-    xmlXPathFreeNodeSetList(xpath); // despite the name, this frees the xpath but not the contained node set
+  xmlXPathFreeNodeSetList(xpath); // despite the name, this frees the xpath but not the contained node set
+}
+
+VALUE Nokogiri_wrap_xml_xpath(xmlXPathObjectPtr xpath)
+{
+  return Data_Wrap_Struct(cNokogiriXmlXpath, 0, deallocate, xpath);
 }
 
 /*
@@ -17,36 +22,18 @@ static VALUE node_set(VALUE self)
   Data_Get_Struct(self, xmlXPathObject, xpath);
 
   if (xpath->nodesetval)
-      return Nokogiri_wrap_xml_node_set(xpath->nodesetval);
-  else
-      return Nokogiri_wrap_xml_node_set(xmlXPathNodeSetCreate(NULL));
-}
+    return Nokogiri_wrap_xml_node_set(xpath->nodesetval);
 
-static VALUE new(VALUE klass, VALUE nodeobj, VALUE search_path)
-{
-  xmlXPathInit();
-
-  xmlNodePtr node ;
-  Data_Get_Struct(nodeobj, xmlNode, node);
-
-  xmlXPathContextPtr ctx = xmlXPathNewContext(node->doc);
-  ctx->node = node ;
-  xmlChar* query = (xmlChar *)StringValuePtr(search_path) ;
-  xmlXPathObjectPtr xpath = xmlXPathEvalExpression(query, ctx );
-  if(xpath == NULL) {
-    xmlXPathFreeContext(ctx);
-    rb_raise(rb_eRuntimeError, "Couldn't evaluate expression '%s'", query);
-  }
-  VALUE self = Data_Wrap_Struct(klass, NULL, free_xpath_object, xpath);
-  xmlXPathFreeContext(ctx);
-
-  return self;
+  return Nokogiri_wrap_xml_node_set(xmlXPathNodeSetCreate(NULL));
 }
 
-VALUE cNokogiriXmlXpath ;
+VALUE cNokogiriXmlXpath;
 void init_xml_xpath(void)
 {
-  VALUE klass = cNokogiriXmlXpath = rb_eval_string("Nokogiri::XML::XPath");
-  rb_define_singleton_method(klass, "new", new, 2);
+  VALUE module = rb_define_module("Nokogiri");
+  VALUE xml = rb_define_module_under(module, "XML");
+  VALUE klass = rb_define_class_under(xml, "XPath", rb_cObject);
+
+  cNokogiriXmlXpath = klass;
   rb_define_method(klass, "node_set", node_set, 0);
 }

ext/nokogiri/xml_xpath.h

@@ -4,6 +4,8 @@
 #include <native.h>
 
 void init_xml_xpath();
+VALUE Nokogiri_wrap_xml_xpath(xmlXPathObjectPtr xpath);
 
-extern VALUE cNokogiriXmlXpath ;
+extern VALUE cNokogiriXmlXpath;
 #endif
+

ext/nokogiri/xml_xpath_context.c

@@ -0,0 +1,51 @@
+#include <xml_xpath_context.h>
+
+static void deallocate(xmlXPathContextPtr ctx)
+{
+  xmlXPathFreeContext(ctx);
+}
+
+/*
+ * call-seq:
+ *  evaluate(search_path)
+ *
+ * Evaluate the +search_path+ returning an XML::XPath object.
+ */
+static VALUE evaluate(VALUE self, VALUE search_path)
+{
+  xmlXPathContextPtr ctx;
+  Data_Get_Struct(self, xmlXPathContext, ctx);
+
+  xmlChar* query = (xmlChar *)StringValuePtr(search_path);
+  xmlXPathObjectPtr xpath = xmlXPathEvalExpression(query, ctx);
+  if(xpath == NULL) {
+    xmlXPathFreeContext(ctx);
+    rb_raise(rb_eRuntimeError, "Couldn't evaluate expression '%s'", query);
+  }
+  return Nokogiri_wrap_xml_xpath(xpath);
+}
+
+static VALUE new(VALUE klass, VALUE nodeobj)
+{
+  xmlXPathInit();
+
+  xmlNodePtr node ;
+  Data_Get_Struct(nodeobj, xmlNode, node);
+
+  xmlXPathContextPtr ctx = xmlXPathNewContext(node->doc);
+  ctx->node = node ;
+  return Data_Wrap_Struct(klass, NULL, deallocate, ctx);
+}
+
+VALUE cNokogiriXmlXpathContext;
+void init_xml_xpath_context(void)
+{
+  VALUE module = rb_define_module("Nokogiri");
+  VALUE xml = rb_define_module_under(module, "XML");
+  VALUE klass = rb_define_class_under(xml, "XPathContext", rb_cObject);
+
+  cNokogiriXmlXpathContext = klass;
+
+  rb_define_singleton_method(klass, "new", new, 1);
+  rb_define_method(klass, "evaluate", evaluate, 1);
+}

ext/nokogiri/xml_xpath_context.h

@@ -0,0 +1,9 @@
+#ifndef NOKOGIRI_XML_XPATH_CONTEXT
+#define NOKOGIRI_XML_XPATH_CONTEXT
+
+#include <native.h>
+
+void init_xml_xpath_context();
+
+extern VALUE cNokogiriXmlXpathContext;
+#endif

lib/nokogiri/xml/node.rb

@@ -44,7 +44,7 @@ def find(*paths)
 
       def find_by_xpath *paths
         sets = paths.map { |path|
-          set = XPath.new(self, path).node_set
+          set = XPathContext.new(self).evaluate(path).node_set
           set.document = document
           document.decorate(set)
           set