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

13 files changed, 218 insertions, 123 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4d50af0..02a9b79 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,7 +18,8 @@ add_executable(
 	src/function/read_xml_file.cc
 	src/function/read_directory.cc
 	src/support/filesystem_context.cc
-	src/support/dom_document_guard.cc
+	src/support/dom/document_cache.cc
+	src/support/dom/document_cache_item.cc
 	src/support/xerces_string_guard.cc
 )
 
diff --git a/dummy/transform.xsl b/dummy/transform.xsl
index 95467ca..62d28c2 100644
--- a/dummy/transform.xsl
+++ b/dummy/transform.xsl
@@ -24,7 +24,17 @@
 		</xsl:for-each>
 		</ul>
 		<ul id="filelist">
-		<xsl:for-each select="external:read-directory('.')/content/item[@type='file']">
+		<xsl:for-each select="external:read-directory('.')[@type='file']">
+			<li><xsl:value-of select="."/></li>
+		</xsl:for-each>
+		</ul>
+		<ul id="filelist2">
+		<xsl:for-each select="external:read-directory('../')[@type='file']">
+			<li><xsl:value-of select="."/></li>
+		</xsl:for-each>
+		</ul>
+		<ul id="filelist3">
+		<xsl:for-each select="external:read-directory('../')[@type='directory']">
 			<li><xsl:value-of select="."/></li>
 		</xsl:for-each>
 		</ul>
diff --git a/src/function/read_directory.cc b/src/function/read_directory.cc
index 9711239..677aa1d 100644
--- a/src/function/read_directory.cc
+++ b/src/function/read_directory.cc
@@ -6,13 +6,15 @@
 #include <xercesc/dom/DOMText.hpp>
 #include <xercesc/util/XMLString.hpp>
 
+#include "support/utility.h"
 #include "support/xerces_string_guard.h"
 
 namespace InputXSLT {
 
-FunctionReadDirectory::FunctionReadDirectory(const FilesystemContext& context):
+FunctionReadDirectory::FunctionReadDirectory(const FilesystemContext& context,
+                                             DomDocumentCache& cache):
 	fs_context_(context),
-	documents_(std::make_shared<std::stack<DomDocumentGuard>>()) { }
+	document_cache_(cache) { }
 
 xalan::XObjectPtr FunctionReadDirectory::execute(
 	xalan::XPathExecutionContext& executionContext,
@@ -20,53 +22,68 @@ xalan::XObjectPtr FunctionReadDirectory::execute(
 	const xalan::XObjectPtr argument,
 	const xalan::Locator*
 ) const {
-	this->documents_->emplace("content");
-	DomDocumentGuard& domDocument = this->documents_->top();
-
-	xercesc::DOMNode* const rootNode = domDocument->getDocumentElement();
+	DomDocumentCache::item* const cachedDocument(
+		this->document_cache_.get(xalanToString(argument->str()))
+	);
 
-	this->fs_context_.iterate(
-		argument->str(),
-		[&domDocument, &rootNode](const boost::filesystem::path& p) {
-		xercesc::DOMElement* const itemNode(
-			domDocument->createElement(*XercesStringGuard("item"))
+	if ( !cachedDocument->isFinalized() ) {
+		xercesc::DOMDocument* const domDocument(
+			cachedDocument->getXercesDocument()
 		);
 
-		switch ( boost::filesystem::status(p).type() ) {
-			case boost::filesystem::regular_file: {
-				itemNode->setAttribute(
-					*XercesStringGuard("type"),
-					*XercesStringGuard("file")
-				);
-
-				break;
-			};
-			case boost::filesystem::directory_file: {
-				itemNode->setAttribute(
-					*XercesStringGuard("type"),
-					*XercesStringGuard("directory")
-				);
-
-				break;
-			};
-			default: {
-				break;
-			};
-		}
-
-		xercesc::DOMText* const textNode(
-			domDocument->createTextNode(
-				*XercesStringGuard(p.filename().string())
-			)
+		xercesc::DOMNode* const rootNode(
+			domDocument->getDocumentElement()
 		);
 
-		itemNode->appendChild(textNode);
-		rootNode->appendChild(itemNode);
-	});
+		this->fs_context_.iterate(
+			argument->str(),
+			[&domDocument, &rootNode](const boost::filesystem::path& p) {
+			xercesc::DOMElement* const itemNode(
+				domDocument->createElement(*XercesStringGuard("item"))
+			);
+
+			switch ( boost::filesystem::status(p).type() ) {
+				case boost::filesystem::regular_file: {
+					itemNode->setAttribute(
+						*XercesStringGuard("type"),
+						*XercesStringGuard("file")
+					);
+
+					break;
+				};
+				case boost::filesystem::directory_file: {
+					itemNode->setAttribute(
+						*XercesStringGuard("type"),
+						*XercesStringGuard("directory")
+					);
+
+					break;
+				};
+				default: {
+					break;
+				};
+			}
+
+			xercesc::DOMText* const textNode(
+				domDocument->createTextNode(
+					*XercesStringGuard(p.filename().string())
+				)
+			);
+
+			itemNode->appendChild(textNode);
+			rootNode->appendChild(itemNode);
+		});
+	}
+
+	xalan::XPathExecutionContext::BorrowReturnMutableNodeRefList nodeList(
+		executionContext
+	);
 
-	return executionContext.getXObjectFactory().createNodeSet(
-		domDocument.finalize()
+	nodeList->addNodes(
+		*cachedDocument->getXalanDocument()->getDocumentElement()->getChildNodes()
 	);
+
+	return executionContext.getXObjectFactory().createNodeSet(nodeList);
 }
 
 FunctionReadDirectory* FunctionReadDirectory::clone(
@@ -76,7 +93,7 @@ FunctionReadDirectory* FunctionReadDirectory::clone(
 
 const xalan::XalanDOMString& FunctionReadDirectory::getError(
 	xalan::XalanDOMString& result) const {
-	result.assign("The read-directory() function expects one argument.");
+	result.assign("The read-directory() function expects one argument of type string.");
 
 	return result;
 }
diff --git a/src/function/read_directory.h b/src/function/read_directory.h
index 782ebed..3fcf389 100644
--- a/src/function/read_directory.h
+++ b/src/function/read_directory.h
@@ -6,18 +6,15 @@
 #include <xalanc/XPath/Function.hpp>
 #include <xalanc/XPath/XObject.hpp>
 
-#include <memory>
-#include <stack>
-
 #include "common.h"
 #include "support/filesystem_context.h"
-#include "support/dom_document_guard.h"
+#include "support/dom/document_cache.h"
 
 namespace InputXSLT {
 
 class FunctionReadDirectory : public xalan::Function {
 	public:
-		FunctionReadDirectory(const FilesystemContext&);
+		FunctionReadDirectory(const FilesystemContext&, DomDocumentCache&);
 
 		virtual xalan::XObjectPtr execute(
 			xalan::XPathExecutionContext&,
@@ -33,10 +30,7 @@ class FunctionReadDirectory : public xalan::Function {
 
 	private:
 		const FilesystemContext& fs_context_;
-
-		std::shared_ptr<
-			std::stack<DomDocumentGuard>
-		> documents_;
+		DomDocumentCache& document_cache_;
 
 		const xalan::XalanDOMString& getError(xalan::XalanDOMString&) const;
 
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_
diff --git a/src/transformation_facade.cc b/src/transformation_facade.cc
index 38dfe93..cb89263 100644
--- a/src/transformation_facade.cc
+++ b/src/transformation_facade.cc
@@ -15,7 +15,8 @@ namespace InputXSLT {
 TransformationFacade::TransformationFacade(const std::string& transformation):
 	fs_context_(boost::filesystem::path(transformation).parent_path().string()),
 	transformation_{},
-	transformer_() {
+	transformer_(),
+	document_cache_() {
 	const xalan::XalanDOMString customNamespace(
 		"http://ExternalFunction.xalan-c++.xml.apache.org"
 	);
@@ -35,7 +36,7 @@ TransformationFacade::TransformationFacade(const std::string& transformation):
 	this->transformer_.installExternalFunction(
 		customNamespace,
 		xalan::XalanDOMString("read-directory"),
-		InputXSLT::FunctionReadDirectory(this->fs_context_)
+		InputXSLT::FunctionReadDirectory(this->fs_context_, this->document_cache_)
 	);
 
 	this->transformer_.compileStylesheet(
diff --git a/src/transformation_facade.h b/src/transformation_facade.h
index 765a376..3acb364 100644
--- a/src/transformation_facade.h
+++ b/src/transformation_facade.h
@@ -7,6 +7,7 @@
 
 #include "common.h"
 #include "support/filesystem_context.h"
+#include "support/dom/document_cache.h"
 
 namespace InputXSLT {
 
@@ -22,6 +23,7 @@ class TransformationFacade {
 		const xalan::XalanCompiledStylesheet* transformation_;
 
 		xalan::XalanTransformer transformer_;
+		DomDocumentCache document_cache_;
 
 };