From f37853fa4f2bbbc60d2fa00f01aaedd8be158767 Mon Sep 17 00:00:00 2001
From: Niels Dekker <N.Dekker@lumc.nl>
Date: Fri, 23 Jun 2017 16:36:42 +0200
Subject: [PATCH] COMP: Fixed <nifti1_io.h> leak into user code

Also on behalf of my colleague Floris Berendsen
Discussed at http://public.kitware.com/pipermail/insight-developers/2017-June/025206.html
With encouraging feedback from Bradley Lowekamp  :-)

Change-Id: I698cbbf66cf6d3c22a3102a3185700da4bf85f2d
---
 Modules/IO/NIFTI/include/itkNiftiImageIO.h | 25 +++++++++++-
 Modules/IO/NIFTI/itk-module.cmake          |  3 +-
 Modules/IO/NIFTI/src/itkNiftiImageIO.cxx   | 44 +++++++++++++++++++++-
 3 files changed, 66 insertions(+), 6 deletions(-)

diff --git a/Modules/IO/NIFTI/include/itkNiftiImageIO.h b/Modules/IO/NIFTI/include/itkNiftiImageIO.h
index 2a7f949f2ec..002b87449dd 100644
--- a/Modules/IO/NIFTI/include/itkNiftiImageIO.h
+++ b/Modules/IO/NIFTI/include/itkNiftiImageIO.h
@@ -23,7 +23,6 @@
 
 #include <fstream>
 #include "itkImageIOBase.h"
-#include <nifti1_io.h>
 
 namespace itk
 {
@@ -128,7 +127,29 @@ class ITKIONIFTI_EXPORT NiftiImageIO:public ImageIOBase
 
   void  SetImageIOMetadataFromNIfTI();
 
-  nifti_image *m_NiftiImage;
+  //This proxy class provides a nifti_image pointer interface to the internal implementation
+  //of itk::NiftiImageIO, while hiding the niftilib interface from the external ITK interface.
+  class NiftiImageProxy;
+
+  //This class has ownership of the proxy and is thereby holder of the nifti_image pointer.
+  class NiftiImageHolder
+  {
+  private:
+    NiftiImageProxy* const m_NiftiImageProxy;
+  public:
+    NiftiImageHolder();
+    ~NiftiImageHolder();
+    NiftiImageProxy& GetNiftiImageProxy();
+
+  private:
+    NiftiImageHolder(const NiftiImageHolder&) ITK_DELETED_FUNCTION;
+    NiftiImageHolder& operator=(const NiftiImageHolder &) ITK_DELETED_FUNCTION;
+  };
+
+  //Note that it is essential that m_NiftiImageHolder is defined before m_NiftiImage, to ensure that
+  //m_NiftiImage can directly get a proxy from m_NiftiImageHolder during NiftiImageIO construction.
+  NiftiImageHolder m_NiftiImageHolder;
+  NiftiImageProxy& m_NiftiImage;
 
   double m_RescaleSlope;
   double m_RescaleIntercept;
diff --git a/Modules/IO/NIFTI/itk-module.cmake b/Modules/IO/NIFTI/itk-module.cmake
index 09a752f0d8b..114cb91d315 100644
--- a/Modules/IO/NIFTI/itk-module.cmake
+++ b/Modules/IO/NIFTI/itk-module.cmake
@@ -3,11 +3,10 @@ set(DOCUMENTATION "This modules contains an ImageIO class to read or write the
 
 itk_module(ITKIONIFTI
   ENABLE_SHARED
-  DEPENDS
-    ITKNIFTI
   PRIVATE_DEPENDS
     ITKIOImageBase
     ITKTransform
+    ITKNIFTI
   TEST_DEPENDS
     ITKTestKernel
     ITKNIFTI
diff --git a/Modules/IO/NIFTI/src/itkNiftiImageIO.cxx b/Modules/IO/NIFTI/src/itkNiftiImageIO.cxx
index 85b98de240c..f6c9682c2d3 100644
--- a/Modules/IO/NIFTI/src/itkNiftiImageIO.cxx
+++ b/Modules/IO/NIFTI/src/itkNiftiImageIO.cxx
@@ -19,6 +19,7 @@
 #include "itkIOCommon.h"
 #include "itkMetaDataObject.h"
 #include "itkSpatialOrientationAdapter.h"
+#include <nifti1_io.h>
 
 namespace itk
 {
@@ -389,8 +390,47 @@ ::GenerateStreamableReadRegionFromRequestedRegion(const ImageIORegion & requeste
   return requestedRegion;
 }
 
-NiftiImageIO::NiftiImageIO():
-  m_NiftiImage(ITK_NULLPTR),
+
+//This internal proxy class provides a pointer-like interface to a nifti_image*, by supporting
+//conversions between proxy and nifti_image pointer and arrow syntax (e.g., m_NiftiImage->data).
+class NiftiImageIO::NiftiImageProxy
+{
+  nifti_image* m_ptr;
+public:
+  NiftiImageProxy(nifti_image* ptr) :
+    m_ptr(ptr)
+  {
+  }
+
+  operator nifti_image*()
+  {
+    return m_ptr;
+  }
+
+  nifti_image* operator->()
+  {
+    return m_ptr;
+  }
+};
+
+NiftiImageIO::NiftiImageHolder::NiftiImageHolder() :
+m_NiftiImageProxy(new NiftiImageProxy(ITK_NULLPTR))
+{
+}
+
+NiftiImageIO::NiftiImageHolder::~NiftiImageHolder()
+{
+  delete m_NiftiImageProxy;
+}
+
+NiftiImageIO::NiftiImageProxy& NiftiImageIO::NiftiImageHolder::GetNiftiImageProxy()
+{
+  return *m_NiftiImageProxy;
+}
+
+
+NiftiImageIO::NiftiImageIO() :
+  m_NiftiImage(m_NiftiImageHolder.GetNiftiImageProxy()),
   m_RescaleSlope(1.0),
   m_RescaleIntercept(0.0),
   m_OnDiskComponentType(UNKNOWNCOMPONENTTYPE),