Improve PyArrayCapsule design by disaplying copy constructor & suppor…

…ting different types via PyCapsule<T> template class

python/bindings/include/openravepy/openravepy_int.h

@@ -217,7 +217,7 @@ class OPENRAVEPY_API PythonGILSaver
     }
 };
 
-// TODO: Remove AutoPyArrayObjectDereferencer in favor of PyArrayCapsule
+// TODO: Remove AutoPyArrayObjectDereferencer in favor of PyCapsule
 class OPENRAVEPY_API AutoPyArrayObjectDereferencer
 {
 public:
@@ -231,51 +231,61 @@ class OPENRAVEPY_API AutoPyArrayObjectDereferencer
     PyArrayObject* _pyarrobj;
 };
 
-class OPENRAVEPY_API PyArrayCapsule
+template<typename T>
+class OPENRAVEPY_API PyCapsule
 {
 public:
-    // \brief the only entrypoint that allows a null pointer. Expects reset to follow
-    PyArrayCapsule()
+    // \brief disables copy constructor to avoid calling Py_DECREF more than once
+    PyCapsule(const PyCapsule<T>&) = delete;
+
+    // \brief the only entrypoint that allows a nullptr. Expects a `reset` call to follow
+    PyCapsule()
       : _ptr(nullptr)
     {
     }
 
     // \param ptr a not-null pointer
-    PyArrayCapsule(PyArrayObject* ptr)
+    PyCapsule(T* ptr)
+      : _ptr(_PreventNullPtr(ptr))
     {
-        reset(ptr);  // Avoid initializer, and use a single entry-point
     }
 
     // \param ptr a not-null pointer
-    void reset(PyArrayObject* ptr)
+    void reset(T* ptr)
     {
-        if (!ptr) {
-            throw OPENRAVE_EXCEPTION_FORMAT0(_("Invalid Numpy-array pointer. Failed to get contiguous array?"), ORE_InvalidArguments);
-        }
-        _ptr = ptr;
+        _ptr = _PreventNullPtr(ptr);
     }
 
-    PyArrayObject* get() const
+    T* get() const
     {
         return _ptr;
     }
 
-    operator PyArrayObject*() const
+    operator T*() const
     {
         return _ptr;
     }
 
-    ~PyArrayCapsule() {
-        if (!_ptr) {
-            return;
+    ~PyCapsule() {
+        if (_ptr != nullptr) {
+            Py_DECREF(_ptr);
         }
-        Py_DECREF(_ptr);
     }
 
 private:
-    PyArrayObject* _ptr;
+    T* _ptr;
+
+    static T* _PreventNullPtr(T* ptr)
+    {
+        if (ptr == nullptr) {
+            throw OPENRAVE_EXCEPTION_FORMAT0(_("Invalid Numpy-array pointer. Failed to get contiguous array?"), ORE_InvalidArguments);
+        }
+        return ptr;
+    }
 };
 
+typedef PyCapsule<PyArrayObject> PyArrayCapsule;
+
 inline RaveVector<float> ExtractFloat3(const py::object& o)
 {
     return RaveVector<float>(py::extract<float>(o[0]), py::extract<float>(o[1]), py::extract<float>(o[2]));