Encapsulated common parts of external function inplementations

* common parts were moved into CRTP template base class _FunctionBase_
* all external functions are derived from that class
** only have to implement _constructDocument_ member method
** currently only supports a single string input parameter which is enough for now
* this change condenses external funtion implementations to the essential and should increase readability as well as maintainability

7 files changed, 130 insertions, 255 deletions

diff --git a/src/function/base.h b/src/function/base.h
new file mode 100644
index 0000000..231800d
--- /dev/null
+++ b/src/function/base.h
@@ -0,0 +1,89 @@
+#ifndef INPUTXSLT_SRC_FUNCTION_BASE_H_
+#define INPUTXSLT_SRC_FUNCTION_BASE_H_
+
+#include <xalanc/XalanTransformer/XalanTransformer.hpp>
+#include <xalanc/XPath/XObjectFactory.hpp>
+#include <xalanc/XPath/Function.hpp>
+#include <xalanc/XPath/XObject.hpp>
+
+#include <memory>
+
+#include "common.h"
+#include "support/dom/document_cache.h"
+#include "support/filesystem_context.h"
+
+namespace InputXSLT {
+
+template <class Implementation>
+class FunctionBase : public xalan::Function {
+	public:
+		FunctionBase():
+			document_cache_(std::make_shared<DomDocumentCache>()) { }
+
+		virtual xalan::XObjectPtr execute(
+			xalan::XPathExecutionContext& executionContext,
+			xalan::XalanNode*,
+			const xalan::XObjectPtr argument,
+			const xalan::Locator* locator
+		) const {
+			const FilesystemContext fsContext(locator);
+
+			const boost::filesystem::path argumentPath(
+				fsContext.resolve(argument->str())
+			);
+
+			DomDocumentCache::optional_item optionalCachedDocument(
+				this->document_cache_->get(argumentPath.string())
+			);
+
+			if ( !optionalCachedDocument.first ) {
+				optionalCachedDocument = this->document_cache_->create(
+					argumentPath.string(),
+					static_cast<Implementation*>(
+						const_cast<FunctionBase*>(this)
+					)->constructDocument(
+						fsContext,
+						argumentPath
+					)
+				);
+			}
+
+			xalan::XPathExecutionContext::BorrowReturnMutableNodeRefList nodeList(
+				executionContext
+			);
+
+			nodeList->addNodes(
+				*optionalCachedDocument.second->getXalanDocument()
+				                              ->getDocumentElement()
+				                              ->getChildNodes()
+			);
+
+			return executionContext.getXObjectFactory().createNodeSet(nodeList);
+		}
+
+		virtual FunctionBase* clone(
+			xalan::MemoryManager& manager) const {
+			return xalan::XalanCopyConstruct(
+				manager,
+				static_cast<const Implementation&>(*this)
+			);
+		}
+
+		FunctionBase& operator=(const FunctionBase&) = delete;
+		bool operator==(const FunctionBase&) const   = delete;
+
+	protected:
+		std::shared_ptr<DomDocumentCache> document_cache_;
+
+		const xalan::XalanDOMString& getError(
+			xalan::XalanDOMString& result) const {
+			result.assign("The function expects one argument of type string.");
+
+			return result;
+		}
+
+};
+
+}
+
+#endif  // INPUTXSLT_SRC_FUNCTION_BASE_H_
diff --git a/src/function/read_directory.cc b/src/function/read_directory.cc
index 48ffa51..8b41dae 100644
--- a/src/function/read_directory.cc
+++ b/src/function/read_directory.cc
@@ -6,13 +6,10 @@
 #include <xercesc/dom/DOMText.hpp>
 
 #include "support/xerces_string_guard.h"
-#include "support/filesystem_context.h"
 
-namespace {
-
-using InputXSLT::XercesStringGuard;
+namespace InputXSLT {
 
-xercesc::DOMDocument* constructDocument(
+xercesc::DOMDocument* FunctionReadDirectory::constructDocument(
 	const InputXSLT::FilesystemContext& fsContext,
 	const boost::filesystem::path& directoryPath
 ) {
@@ -84,58 +81,3 @@ xercesc::DOMDocument* constructDocument(
 }
 
 }
-
-namespace InputXSLT {
-
-FunctionReadDirectory::FunctionReadDirectory():
-	document_cache_(std::make_shared<DomDocumentCache>()) { }
-
-xalan::XObjectPtr FunctionReadDirectory::execute(
-	xalan::XPathExecutionContext& executionContext,
-	xalan::XalanNode*,
-	const xalan::XObjectPtr argument,
-	const xalan::Locator* locator
-) const {
-	const FilesystemContext fsContext(locator);
-
-	const boost::filesystem::path directoryPath(
-		fsContext.resolve(argument->str())
-	);
-
-	DomDocumentCache::optional_item optionalCachedDocument(
-		this->document_cache_->get(directoryPath.string())
-	);
-
-	if ( !optionalCachedDocument.first ) {
-		optionalCachedDocument = this->document_cache_->create(
-			directoryPath.string(),
-			constructDocument(fsContext, directoryPath)
-		);
-	}
-
-	xalan::XPathExecutionContext::BorrowReturnMutableNodeRefList nodeList(
-		executionContext
-	);
-
-	nodeList->addNodes(
-		*optionalCachedDocument.second->getXalanDocument()
-		                              ->getDocumentElement()
-		                              ->getChildNodes()
-	);
-
-	return executionContext.getXObjectFactory().createNodeSet(nodeList);
-}
-
-FunctionReadDirectory* FunctionReadDirectory::clone(
-	xalan::MemoryManager& manager) const {
-	return xalan::XalanCopyConstruct(manager, *this);
-}
-
-const xalan::XalanDOMString& FunctionReadDirectory::getError(
-	xalan::XalanDOMString& result) const {
-	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 02a0305..2c28642 100644
--- a/src/function/read_directory.h
+++ b/src/function/read_directory.h
@@ -1,38 +1,21 @@
 #ifndef INPUTXSLT_SRC_FUNCTION_READ_DIRECTORY_H_
 #define INPUTXSLT_SRC_FUNCTION_READ_DIRECTORY_H_
 
-#include <xalanc/XalanTransformer/XalanTransformer.hpp>
-#include <xalanc/XPath/XObjectFactory.hpp>
-#include <xalanc/XPath/Function.hpp>
-#include <xalanc/XPath/XObject.hpp>
-
-#include <memory>
-
-#include "common.h"
-#include "support/dom/document_cache.h"
+#include "base.h"
 
 namespace InputXSLT {
 
-class FunctionReadDirectory : public xalan::Function {
+class FunctionReadDirectory : public FunctionBase<FunctionReadDirectory> {
 	public:
-		FunctionReadDirectory();
-
-		virtual xalan::XObjectPtr execute(
-			xalan::XPathExecutionContext&,
-			xalan::XalanNode*,
-			const xalan::XObjectPtr,
-			const xalan::Locator*
-		) const;
-
-		virtual FunctionReadDirectory* clone(xalan::MemoryManager&) const;
-
-		FunctionReadDirectory& operator=(const FunctionReadDirectory&) = delete;
-		bool operator==(const FunctionReadDirectory&) const            = delete;
+		using FunctionBase<FunctionReadDirectory>::FunctionBase;
 
-	private:
-		std::shared_ptr<DomDocumentCache> document_cache_;
+	protected:
+		friend FunctionBase<FunctionReadDirectory>;
 
-		const xalan::XalanDOMString& getError(xalan::XalanDOMString&) const;
+		xercesc::DOMDocument* constructDocument(
+			const FilesystemContext&,
+			const boost::filesystem::path&
+		);
 
 };
 
diff --git a/src/function/read_file.cc b/src/function/read_file.cc
index ba94909..439d905 100644
--- a/src/function/read_file.cc
+++ b/src/function/read_file.cc
@@ -8,12 +8,9 @@
 #include "boost/filesystem/fstream.hpp"
 
 #include "support/xerces_string_guard.h"
-#include "support/filesystem_context.h"
 
 namespace {
 
-using InputXSLT::XercesStringGuard;
-
 inline std::string readFile(const boost::filesystem::path& filePath) {
 	boost::filesystem::ifstream file(filePath);
 
@@ -23,7 +20,12 @@ inline std::string readFile(const boost::filesystem::path& filePath) {
 	);
 }
 
-xercesc::DOMDocument* constructDocument(
+}
+
+namespace InputXSLT {
+
+xercesc::DOMDocument* FunctionReadFile::constructDocument(
+	const FilesystemContext&,
 	const boost::filesystem::path& filePath
 ) {
 	xercesc::DOMDocument* const domDocument(
@@ -68,58 +70,3 @@ xercesc::DOMDocument* constructDocument(
 }
 
 }
-
-namespace InputXSLT {
-
-FunctionReadFile::FunctionReadFile():
-	document_cache_(std::make_shared<DomDocumentCache>()) { }
-
-xalan::XObjectPtr FunctionReadFile::execute(
-	xalan::XPathExecutionContext& executionContext,
-	xalan::XalanNode*,
-	const xalan::XObjectPtr argument,
-	const xalan::Locator* locator
-) const {
-	const FilesystemContext fsContext(locator);
-
-	const boost::filesystem::path filePath(
-		fsContext.resolve(argument->str())
-	);
-
-	DomDocumentCache::optional_item optionalCachedDocument(
-		this->document_cache_->get(filePath.string())
-	);
-
-	if ( !optionalCachedDocument.first ) {
-		optionalCachedDocument = this->document_cache_->create(
-			filePath.string(),
-			constructDocument(filePath)
-		);
-	}
-
-	xalan::XPathExecutionContext::BorrowReturnMutableNodeRefList nodeList(
-		executionContext
-	);
-
-	nodeList->addNodes(
-		*optionalCachedDocument.second->getXalanDocument()
-		                              ->getDocumentElement()
-		                              ->getChildNodes()
-	);
-
-	return executionContext.getXObjectFactory().createNodeSet(nodeList);
-}
-
-FunctionReadFile* FunctionReadFile::clone(
-	xalan::MemoryManager& manager) const {
-	return xalan::XalanCopyConstruct(manager, *this);
-}
-
-const xalan::XalanDOMString& FunctionReadFile::getError(
-	xalan::XalanDOMString& result) const {
-	result.assign("The read-file() function expects one argument of type string.");
-
-	return result;
-}
-
-}
diff --git a/src/function/read_file.h b/src/function/read_file.h
index 65746a5..fd36847 100644
--- a/src/function/read_file.h
+++ b/src/function/read_file.h
@@ -1,38 +1,21 @@
 #ifndef INPUTXSLT_SRC_FUNCTION_READ_FILE_H_
 #define INPUTXSLT_SRC_FUNCTION_READ_FILE_H_
 
-#include <xalanc/XalanTransformer/XalanTransformer.hpp>
-#include <xalanc/XPath/XObjectFactory.hpp>
-#include <xalanc/XPath/Function.hpp>
-#include <xalanc/XPath/XObject.hpp>
-
-#include <string>
-
-#include "common.h"
-#include "support/dom/document_cache.h"
+#include "base.h"
 
 namespace InputXSLT {
 
-class FunctionReadFile : public xalan::Function {
+class FunctionReadFile : public FunctionBase<FunctionReadFile> {
 	public:
-		FunctionReadFile();
-
-		virtual xalan::XObjectPtr execute(
-			xalan::XPathExecutionContext&,
-			xalan::XalanNode*,
-			const xalan::XObjectPtr,
-			const xalan::Locator*
-		) const;
-
-		virtual FunctionReadFile* clone(xalan::MemoryManager&) const;
-
-		FunctionReadFile& operator=(const FunctionReadFile&) = delete;
-		bool operator==(const FunctionReadFile&) const       = delete;
+		using FunctionBase<FunctionReadFile>::FunctionBase;
 
-	private:
-		std::shared_ptr<DomDocumentCache> document_cache_;
+	protected:
+		friend FunctionBase<FunctionReadFile>;
 
-		const xalan::XalanDOMString& getError(xalan::XalanDOMString&) const;
+		xercesc::DOMDocument* constructDocument(
+			const FilesystemContext&,
+			const boost::filesystem::path&
+		);
 
 };
 
diff --git a/src/function/read_xml_file.cc b/src/function/read_xml_file.cc
index a4e3e3c..71ba819 100644
--- a/src/function/read_xml_file.cc
+++ b/src/function/read_xml_file.cc
@@ -9,7 +9,6 @@
 #include "boost/filesystem/fstream.hpp"
 
 #include "support/xerces_string_guard.h"
-#include "support/filesystem_context.h"
 
 namespace {
 
@@ -29,7 +28,12 @@ inline xercesc::DOMNode* importDocumentElement(
 	);
 }
 
-xercesc::DOMDocument* constructDocument(
+}
+
+namespace InputXSLT {
+
+xercesc::DOMDocument* FunctionReadXmlFile::constructDocument(
+	const FilesystemContext&,
 	const boost::filesystem::path& filePath
 ) {
 	xercesc::DOMDocument* const domDocument(
@@ -72,58 +76,3 @@ xercesc::DOMDocument* constructDocument(
 }
 
 }
-
-namespace InputXSLT {
-
-FunctionReadXmlFile::FunctionReadXmlFile():
-	document_cache_(std::make_shared<DomDocumentCache>()) { }
-
-xalan::XObjectPtr FunctionReadXmlFile::execute(
-	xalan::XPathExecutionContext& executionContext,
-	xalan::XalanNode*,
-	const xalan::XObjectPtr argument,
-	const xalan::Locator* locator
-) const {
-	const FilesystemContext fsContext(locator);
-
-	const boost::filesystem::path filePath(
-		fsContext.resolve(argument->str())
-	);
-
-	DomDocumentCache::optional_item optionalCachedDocument(
-		this->document_cache_->get(filePath.string())
-	);
-
-	if ( !optionalCachedDocument.first ) {
-		optionalCachedDocument = this->document_cache_->create(
-			filePath.string(),
-			constructDocument(filePath)
-		);
-	}
-
-	xalan::XPathExecutionContext::BorrowReturnMutableNodeRefList nodeList(
-		executionContext
-	);
-
-	nodeList->addNodes(
-		*optionalCachedDocument.second->getXalanDocument()
-		                              ->getDocumentElement()
-		                              ->getChildNodes()
-	);
-
-	return executionContext.getXObjectFactory().createNodeSet(nodeList);
-}
-
-FunctionReadXmlFile* FunctionReadXmlFile::clone(
-	xalan::MemoryManager& manager) const {
-	return xalan::XalanCopyConstruct(manager, *this);
-}
-
-const xalan::XalanDOMString& FunctionReadXmlFile::getError(
-	xalan::XalanDOMString& result) const {
-	result.assign("The read-xml-file() function expects one argument of type string.");
-
-	return result;
-}
-
-}
diff --git a/src/function/read_xml_file.h b/src/function/read_xml_file.h
index d7ef440..5314b4a 100644
--- a/src/function/read_xml_file.h
+++ b/src/function/read_xml_file.h
@@ -1,39 +1,21 @@
 #ifndef INPUTXSLT_SRC_FUNCTION_READ_XML_FILE_H_
 #define INPUTXSLT_SRC_FUNCTION_READ_XML_FILE_H_
 
-#include <xalanc/XalanTransformer/XalanTransformer.hpp>
-#include <xalanc/XPath/XObjectFactory.hpp>
-#include <xalanc/XPath/Function.hpp>
-#include <xalanc/XPath/XObject.hpp>
-
-#include <string>
-#include <memory>
-
-#include "common.h"
-#include "support/dom/document_cache.h"
+#include "base.h"
 
 namespace InputXSLT {
 
-class FunctionReadXmlFile : public xalan::Function {
+class FunctionReadXmlFile : public FunctionBase<FunctionReadXmlFile> {
 	public:
-		FunctionReadXmlFile();
-
-		virtual xalan::XObjectPtr execute(
-			xalan::XPathExecutionContext&,
-			xalan::XalanNode*,
-			const xalan::XObjectPtr,
-			const xalan::Locator*
-		) const;
-
-		virtual FunctionReadXmlFile* clone(xalan::MemoryManager&) const;
-
-		FunctionReadXmlFile& operator=(const FunctionReadXmlFile&) = delete;
-		bool operator==(const FunctionReadXmlFile&) const          = delete;
+		using FunctionBase<FunctionReadXmlFile>::FunctionBase;
 
-	private:
-		std::shared_ptr<DomDocumentCache> document_cache_;
+	protected:
+		friend FunctionBase<FunctionReadXmlFile>;
 
-		const xalan::XalanDOMString& getError(xalan::XalanDOMString& result) const;
+		xercesc::DOMDocument* constructDocument(
+			const FilesystemContext&,
+			const boost::filesystem::path&
+		);
 
 };