Added XercesStringGuard scope-guard to manage XMLCh

* xercesc requires XMLCh* strings to be hand-allocated and released using the XMLString class
* XercesStringGuard works as a scope-guard for XMLCh* string lifetime and greatly simplifies xerces DOM construction

3 files changed, 60 insertions, 20 deletions

diff --git a/src/function/read_directory.cc b/src/function/read_directory.cc
index 22653b6..245f311 100644
--- a/src/function/read_directory.cc
+++ b/src/function/read_directory.cc
@@ -6,6 +6,8 @@
 #include <xercesc/dom/DOMText.hpp>
 #include <xercesc/util/XMLString.hpp>
 
+#include "support/xerces_string_guard.h"
+
 namespace InputXSLT {
 
 FunctionReadDirectory::FunctionReadDirectory(const FilesystemContext& context):
@@ -34,31 +36,27 @@ xalan::XObjectPtr FunctionReadDirectory::execute(
 	this->fs_context_.iterate(
 		arguments[0]->str(),
 		[&domDocument, &rootNode](const boost::filesystem::path& p) {
-		XMLCh* buffer = xercesc::XMLString::transcode("item");
-		xercesc::DOMElement* const itemNode = domDocument->createElement(buffer);
-		xercesc::XMLString::release(&buffer);
-
-		buffer = xercesc::XMLString::transcode("type");
+		xercesc::DOMElement* const itemNode(
+			domDocument->createElement(*XercesStringGuard("item"))
+		);
 
 		if ( boost::filesystem::is_regular_file(p) ) {
-			XMLCh* valueBuffer = xercesc::XMLString::transcode("file");
-
-			itemNode->setAttribute(buffer, valueBuffer);
-
-			xercesc::XMLString::release(&valueBuffer);
+			itemNode->setAttribute(
+				*XercesStringGuard("type"),
+				*XercesStringGuard("file")
+			);
 		} else if ( boost::filesystem::is_directory(p) ) {
-			XMLCh* valueBuffer = xercesc::XMLString::transcode("directory");
-
-			itemNode->setAttribute(buffer, valueBuffer);
-
-			xercesc::XMLString::release(&valueBuffer);
+			itemNode->setAttribute(
+				*XercesStringGuard("type"),
+				*XercesStringGuard("directory")
+			);
 		}
 
-		xercesc::XMLString::release(&buffer);
-
-		buffer = xercesc::XMLString::transcode(p.filename().string().data());
-		xercesc::DOMText* const textNode = domDocument->createTextNode(buffer);
-		xercesc::XMLString::release(&buffer);
+		xercesc::DOMText* const textNode(
+			domDocument->createTextNode(
+				*XercesStringGuard(p.filename().string())
+			)
+		);
 
 		itemNode->appendChild(textNode);
 		rootNode->appendChild(itemNode);
diff --git a/src/support/xerces_string_guard.cc b/src/support/xerces_string_guard.cc
new file mode 100644
index 0000000..14ad29b
--- /dev/null
+++ b/src/support/xerces_string_guard.cc
@@ -0,0 +1,18 @@
+#include "xerces_string_guard.h"
+
+namespace InputXSLT {
+
+XercesStringGuard::XercesStringGuard(const std::string& src):
+	string_(xercesc::XMLString::transcode(src.data())) { }
+
+XercesStringGuard::~XercesStringGuard() {
+	xercesc::XMLString::release(
+		const_cast<XMLCh**>(&this->string_)
+	);
+}
+
+XMLCh* XercesStringGuard::operator*() {
+	return this->string_;
+}
+
+}
diff --git a/src/support/xerces_string_guard.h b/src/support/xerces_string_guard.h
new file mode 100644
index 0000000..f64a53e
--- /dev/null
+++ b/src/support/xerces_string_guard.h
@@ -0,0 +1,24 @@
+#ifndef INPUTXSLT_SRC_SUPPORT_XERCES_STRING_GUARD_H_
+#define INPUTXSLT_SRC_SUPPORT_XERCES_STRING_GUARD_H_
+
+#include <xercesc/util/XMLString.hpp>
+
+#include <string>
+
+namespace InputXSLT {
+
+class XercesStringGuard {
+	public:
+		XercesStringGuard(const std::string&);
+		~XercesStringGuard();
+
+		XMLCh* operator*();
+
+	private:
+		XMLCh* const string_;
+
+};
+
+}
+
+#endif  // INPUTXSLT_SRC_SUPPORT_XERCES_STRING_GUARD_H_