Use boost::shared_ptr to always free memory

Author: hadley

src/xml2_node.cpp

@@ -1,9 +1,9 @@
 #include <Rcpp.h>
 #include <libxml/tree.h>
+#include <boost/shared_ptr.hpp>
 
 using namespace Rcpp;
 #include "xml2_types.h"
-#include "xml2_utils.h"
 
 // [[Rcpp::export]]
 CharacterVector node_name(XPtrNode node) {
@@ -12,36 +12,22 @@ CharacterVector node_name(XPtrNode node) {
 
 // [[Rcpp::export]]
 CharacterVector node_text(XPtrNode node) {
-  xmlChar* s = xmlNodeGetContent(node.get());
-  CharacterVector out = xmlCharToRChar(s);
-  if (s != NULL)
-    xmlFree(s);
-
-  return out;
+  return Xml2Char(xmlNodeGetContent(node.get())).string();
 }
 
 // [[Rcpp::export]]
 CharacterVector node_attr(XPtrNode node, std::string name) {
-  xmlChar* s = xmlGetProp(node.get(), (xmlChar*) name.c_str());
-
-  CharacterVector out = xmlCharToRChar(s);
-  if (s != NULL)
-    xmlFree(s);
-
-  return out;
+  return Xml2Char(xmlGetProp(node.get(), (xmlChar*) name.c_str())).string();
 }
 
 // [[Rcpp::export]]
 CharacterVector node_format(XPtrDoc doc, XPtrNode node,
                             bool format = true,
                             int indent = 0) {
-  xmlBufferPtr buffer = xmlBufferCreate();
-  xmlNodeDump(buffer, doc.get(), node.get(), indent, format);
+  boost::shared_ptr<xmlBuffer> buffer(xmlBufferCreate(), xmlFree);
+  xmlNodeDump(buffer.get(), doc.get(), node.get(), indent, format);
 
-  CharacterVector out = xmlCharToRChar(buffer->content);
-  xmlFree(buffer);
-
-  return out;
+  return xmlCharToRChar(buffer->content);
 }
 
 // [[Rcpp::export]]
@@ -70,10 +56,6 @@ void node_write(XPtrNode n, XPtrDoc d, std::string path) {
 
 // [[Rcpp::export]]
 CharacterVector node_path(XPtrNode n) {
-  xmlChar* s = xmlGetNodePath(n.get());
-  CharacterVector out = xmlCharToRChar(s);
-  if (s != NULL)
-    xmlFree(s);
-
-  return out;
+  return Xml2Char(xmlGetNodePath(n.get())).string();
 }
+

src/xml2_types.h

@@ -1,9 +1,10 @@
 #ifndef __XML2_XML2_TYPES__
 #define __XML2_XML2_TYPES__
 
-#include <RcppCommon.h>
-#include <libxml/parser.h>
+#include "xml2_utils.h"
 #include "XmlPushParser.h"
+#include <libxml/tree.h>
+#include <Rcpp.h>
 
 inline void finaliseNode(xmlNode* node) {
   // do nothing

src/xml2_utils.h

@@ -3,6 +3,7 @@
 
 #include <Rcpp.h>
 #include <libxml/tree.h>
+#include <boost/shared_ptr.hpp>
 
 inline Rcpp::CharacterVector xmlCharToRChar(const xmlChar* x) {
   if (x == NULL)
@@ -14,4 +15,16 @@ inline Rcpp::CharacterVector xmlCharToRChar(const xmlChar* x) {
   return out;
 }
 
+// A wrapper around xmlChar* that always frees memory
+class Xml2Char {
+  boost::shared_ptr<xmlChar> string_;
+
+public:
+  Xml2Char(xmlChar* string): string_(string, xmlFree) {}
+
+  Rcpp::CharacterVector string() {
+    return xmlCharToRChar(string_.get());
+  }
+};
+
 #endif

src/xml2_xpath.cpp

@@ -6,23 +6,23 @@ using namespace Rcpp;
 
 // [[Rcpp::export]]
 Rcpp::List node_search(XPtrNode node, XPtrDoc doc, std::string xpath) {
-  xmlXPathContextPtr context = xmlXPathNewContext(doc.get());
-  xmlXPathObjectPtr result = xmlXPathNodeEval(
-    node.get(),
-    (xmlChar*) xpath.c_str(),
-    context
+
+  boost::shared_ptr<xmlXPathContext> context(
+      xmlXPathNewContext(doc.get()),
+      xmlXPathFreeContext
+  );
+  boost::shared_ptr<xmlXPathObject> result(
+    xmlXPathNodeEval(node.get(), (xmlChar*) xpath.c_str(), context.get()),
+    xmlXPathFreeObject
   );
-  xmlXPathFreeContext(context);
 
   if (result->type != XPATH_NODESET) {
-    xmlXPathFreeObject(result);
     Rcpp::stop("Currently only nodeset results are supported");
   }
 
   // Return an empty list if there are no matches
   xmlNodeSetPtr nodes = result->nodesetval;
   if (xmlXPathNodeSetIsEmpty(nodes)) {
-    xmlXPathFreeObject(result);
     return Rcpp::List::create();
   }
 
@@ -31,8 +31,6 @@ Rcpp::List node_search(XPtrNode node, XPtrDoc doc, std::string xpath) {
   for (int i = 0; i < nodes->nodeNr; i++) {
     out[i] = XPtrNode(nodes->nodeTab[i]);
   }
-  xmlXPathFreeObject(result);
-
 
   return out;
 }