add placeholder skeleton for MCPL-input

include/openmc/source.h

@@ -100,6 +100,25 @@ private:
   vector<SourceSite> sites_; //!< Source sites from a file
 };
 
+//==============================================================================
+// MCPL-file input source
+//==============================================================================
+class MCPLFileSource : public Source {
+public:
+  // Constructors, destructors
+  MCPLFileSource(std::string path);
+  ~MCPLFileSource();
+
+  // Defer implementation to custom source library
+  SourceSite sample(uint64_t* seed) const override
+
+private:
+  vector <SourceSite> sites_; //!<source sites from an MCPL-file
+};
+
+
+
+
 //==============================================================================
 //! Wrapper for custom sources that manages opening/closing shared library
 //==============================================================================

src/source.cpp

@@ -332,6 +332,27 @@ CustomSourceWrapper::~CustomSourceWrapper()
 #endif
 }
 
+//===========================================================================
+// Read an MCPL-file
+//===========================================================================
+MCPLFileSource::MCPLFileSource(std::string path)
+{
+  // Check if source file exists
+  if (!file_exists(path)) {
+    fatal_error(fmt::format("Source file '{}' does not exist.", path));
+  }
+   
+  // Read the source from a binary file instead of sampling from some
+  // assumed source distribution
+  write_message(6, "Reading source file from {}...", path);
+
+  // Open the mcpl file
+  id_t file_id = mcpl_open(path.c_str)
+  
+
+}
+
+
 //==============================================================================
 // Non-member functions
 //==============================================================================