Implemented global DOM document cache

* the plan to return XML-nodes from each external function requires a better way to manage the lifetime of many xerces DOM document instances and their support class instances
** this is why DomDocumentCache and DomDocumentCache::item were implemented
** based on std::map so we can easily access the result of old function calls
* changed external read-directory function to return the children of the document node instead of the document node itself
** removes unnecessary cruft in function calls
** will make returning status codes alongside the function result more pleasing to the eye
* updated test transformation to reflect new features

7 files changed, 137 insertions, 67 deletions

diff --git a/src/support/dom/document_cache.cc b/src/support/dom/document_cache.cc
new file mode 100644
index 0000000..f814559
--- /dev/null
+++ b/src/support/dom/document_cache.cc
@@ -0,0 +1,26 @@
+#include "document_cache.h"
+
+namespace InputXSLT {
+
+DomDocumentCache::DomDocumentCache():
+	map_() { }
+
+DomDocumentCache::item* DomDocumentCache::get(const std::string& key) {
+	auto itemIter = this->map_.find(key);
+
+	if ( itemIter == this->map_.end() ) {
+		auto result = this->map_.emplace(
+			std::make_pair(key, std::unique_ptr<item>(new item("content")))
+		);
+
+		if ( result.second ) {
+			return (*(result.first)).second.get();
+		} else {
+			return nullptr;
+		}
+	} else {
+		return (*itemIter).second.get();
+	}
+}
+
+}
diff --git a/src/support/dom/document_cache.h b/src/support/dom/document_cache.h
new file mode 100644
index 0000000..4447a18
--- /dev/null
+++ b/src/support/dom/document_cache.h
@@ -0,0 +1,27 @@
+#ifndef INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_CACHE_H_
+#define INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_CACHE_H_
+
+#include <map>
+#include <string>
+#include <memory>
+
+namespace InputXSLT {
+
+class DomDocumentCache {
+	public:
+		class item;
+
+		DomDocumentCache();
+
+		item* get(const std::string&);
+
+	private:
+		std::map<std::string, std::unique_ptr<item>> map_;
+
+};
+
+}
+
+#include "document_cache_item.h"
+
+#endif  // INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_CACHE_H_
diff --git a/src/support/dom/document_cache_item.cc b/src/support/dom/document_cache_item.cc
new file mode 100644
index 0000000..8cc1c24
--- /dev/null
+++ b/src/support/dom/document_cache_item.cc
@@ -0,0 +1,50 @@
+#include "support/dom/document_cache_item.h"
+
+#include <xercesc/dom/DOMImplementation.hpp>
+#include <xercesc/util/XMLString.hpp>
+
+#include "support/xerces_string_guard.h"
+
+namespace InputXSLT {
+
+DomDocumentCache::item::item(const std::string& rootNode):
+	parser_(),
+	dom_support_(parser_),
+	document_(
+		xercesc::DOMImplementation::getImplementation()->createDocument(
+			nullptr,
+			*XercesStringGuard(rootNode),
+			nullptr
+		)
+	),
+	parsed_source_() { }
+
+DomDocumentCache::item::~item() {
+	this->document_->release();
+}
+
+bool DomDocumentCache::item::isFinalized() const {
+	return static_cast<bool>(this->parsed_source_);
+}
+
+xercesc::DOMDocument* DomDocumentCache::item::getXercesDocument() const {
+	return this->document_;
+}
+
+xalan::XalanDocument* DomDocumentCache::item::getXalanDocument() {
+	if ( this->parsed_source_ ) {
+		return this->parsed_source_->getDocument();
+	} else {
+		this->parsed_source_.reset(
+			new xalan::XercesDOMWrapperParsedSource(
+					document_,
+					parser_,
+					dom_support_
+			)
+		);
+
+		return this->parsed_source_->getDocument();
+	}
+}
+
+}
diff --git a/src/support/dom_document_guard.h b/src/support/dom/document_cache_item.h
index decca01..1f7152b 100644
--- a/src/support/dom_document_guard.h
+++ b/src/support/dom/document_cache_item.h
@@ -1,5 +1,5 @@
-#ifndef INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_GUARD_H_
-#define INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_GUARD_H_
+#ifndef INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_CACHE_ITEM_H_
+#define INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_CACHE_ITEM_H_
 
 #include <xalanc/XercesParserLiaison/XercesParserLiaison.hpp>
 #include <xalanc/XercesParserLiaison/XercesDOMSupport.hpp>
@@ -11,21 +11,27 @@
 #include <memory>
 
 #include "common.h"
+#include "document_cache.h"
 
 namespace InputXSLT {
 
-class DomDocumentGuard {
+class DomDocumentCache::item {
 	public:
-		DomDocumentGuard(const std::string&);
-		~DomDocumentGuard();
+		~item();
 
-		xercesc::DOMDocument* operator->();
-		xalan::XalanDocument* finalize();
+		bool isFinalized() const;
+
+		xercesc::DOMDocument* getXercesDocument() const;
+		xalan::XalanDocument* getXalanDocument();
+
+	protected:
+		friend DomDocumentCache;
+
+		item(const std::string&);
 
 	private:
 		xalan::XercesParserLiaison parser_;
 		xalan::XercesDOMSupport dom_support_;
-		XMLCh* root_node_name_;
 		xercesc::DOMDocument* const document_;
 		std::unique_ptr<xalan::XercesDOMWrapperParsedSource> parsed_source_;
 
@@ -33,4 +39,4 @@ class DomDocumentGuard {
 
 }
 
-#endif  // INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_GUARD_H_
+#endif  // INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_CACHE_ITEM_H_
diff --git a/src/support/dom_document_guard.cc b/src/support/dom_document_guard.cc
deleted file mode 100644
index a83345f..0000000
--- a/src/support/dom_document_guard.cc
+++ /dev/null
@@ -1,45 +0,0 @@
-#include "support/dom_document_guard.h"
-
-#include <xercesc/dom/DOMImplementation.hpp>
-#include <xercesc/util/XMLString.hpp>
-
-namespace InputXSLT {
-
-DomDocumentGuard::DomDocumentGuard(const std::string& rootNode):
-	parser_(),
-	dom_support_(parser_),
-	root_node_name_(
-		xercesc::XMLString::transcode(rootNode.data())
-	),
-	document_(
-		xercesc::DOMImplementation::getImplementation()->createDocument(
-			nullptr,
-			root_node_name_,
-			nullptr
-		)
-	),
-	parsed_source_() { }
-
-DomDocumentGuard::~DomDocumentGuard() {
-	xercesc::XMLString::release(&this->root_node_name_);
-
-	this->document_->release();
-}
-
-xercesc::DOMDocument* DomDocumentGuard::operator->() {
-	return this->document_;
-}
-
-xalan::XalanDocument* DomDocumentGuard::finalize() {
-	this->parsed_source_.reset(
-		new xalan::XercesDOMWrapperParsedSource(
-				document_,
-				parser_,
-				dom_support_
-		)
-	);
-
-	return this->parsed_source_->getDocument();
-}
-
-}
diff --git a/src/support/filesystem_context.cc b/src/support/filesystem_context.cc
index baeccf3..9ed9bbf 100644
--- a/src/support/filesystem_context.cc
+++ b/src/support/filesystem_context.cc
@@ -1,18 +1,6 @@
 #include "filesystem_context.h"
 
-namespace {
-
-inline std::string xalanToString(const xalan::XalanDOMString& text) {
-	xalan::CharVectorType castHelper;
-	text.transcode(castHelper);
-
-	return std::string(
-		castHelper.begin(),
-		castHelper.end() - 1
-	);
-}
-
-}
+#include "support/utility.h"
 
 namespace InputXSLT {
 
diff --git a/src/support/utility.h b/src/support/utility.h
new file mode 100644
index 0000000..4c63c72
--- /dev/null
+++ b/src/support/utility.h
@@ -0,0 +1,18 @@
+#ifndef INPUTXSLT_SRC_SUPPORT_UTILITY_H_
+#define INPUTXSLT_SRC_SUPPORT_UTILITY_H_
+
+namespace {
+
+inline std::string xalanToString(const xalan::XalanDOMString& text) {
+	xalan::CharVectorType castHelper;
+	text.transcode(castHelper);
+
+	return std::string(
+		castHelper.begin(),
+		castHelper.end() - 1
+	);
+}
+
+}
+
+#endif  // INPUTXSLT_SRC_SUPPORT_UTILITY_H_