Add aux kernel to read buffer content (idaholab#401)

include/auxkernels/FFTBufferAux.h

@@ -0,0 +1,32 @@
+/**********************************************************************/
+/*                     DO NOT MODIFY THIS HEADER                      */
+/* MAGPIE - Mesoscale Atomistic Glue Program for Integrated Execution */
+/*                                                                    */
+/*            Copyright 2017 Battelle Energy Alliance, LLC            */
+/*                        ALL RIGHTS RESERVED                         */
+/**********************************************************************/
+
+#pragma once
+
+#include "AuxKernel.h"
+
+class FFTBufferAux;
+template <typename T>
+class FFTBufferBase;
+
+template <>
+InputParameters validParams<FFTBufferAux>();
+
+/**
+ *
+ */
+class FFTBufferAux : public AuxKernel
+{
+public:
+  FFTBufferAux(const InputParameters & parameters);
+
+protected:
+  virtual Real computeValue() override;
+
+  const FFTBufferBase<Real> & _buffer;
+};

src/auxkernels/FFTBufferAux.C

@@ -0,0 +1,33 @@
+/**********************************************************************/
+/*                     DO NOT MODIFY THIS HEADER                      */
+/* MAGPIE - Mesoscale Atomistic Glue Program for Integrated Execution */
+/*                                                                    */
+/*            Copyright 2017 Battelle Energy Alliance, LLC            */
+/*                        ALL RIGHTS RESERVED                         */
+/**********************************************************************/
+
+#include "FFTBufferAux.h"
+#include "FFTBufferBase.h"
+
+registerMooseObject("MagpieApp", FFTBufferAux);
+
+template <>
+InputParameters
+validParams<FFTBufferAux>()
+{
+  InputParameters params = validParams<AuxKernel>();
+  params.addClassDescription("Fetch values from an FFT buffer.");
+  params.addRequiredParam<UserObjectName>("fft_buffer", "Real valued FFT buffer object");
+  return params;
+}
+
+FFTBufferAux::FFTBufferAux(const InputParameters & parameters)
+  : AuxKernel(parameters), _buffer(getUserObject<FFTBufferBase<Real>>("fft_buffer"))
+{
+}
+
+Real
+FFTBufferAux::computeValue()
+{
+  return _buffer(_current_elem->centroid());
+}