central access to CORSIKA_DATA path

Framework/Utilities/CMakeLists.txt

@@ -20,10 +20,12 @@ endif ()
 set (
   UTILITIES_SOURCES  
   COMBoost.cc
+  CorsikaData.cc
   ${CORSIKA_FENV})
 
 set (
   UTILITIES_HEADERS
+  CorsikaData.h
   COMBoost.h
   Bit.h
   Singleton.h

Framework/Utilities/CorsikaData.cc

+#include <corsika/utl/CorsikaData.h>
+
+#include <cstdlib>
+#include <stdexcept>
+#include <string>
+
+std::filesystem::path corsika::utl::CorsikaData(std::filesystem::path const& key) {
+  if (auto const* p = std::getenv("CORSIKA_DATA"); p != nullptr) {
+    auto const path = std::filesystem::path(p) / key;
+    return path;
+  } else {
+    throw std::runtime_error("CORSIKA_DATA not set");
+  }
+}

Framework/Utilities/CorsikaData.h

+/*
+ * (c) Copyright 2020 CORSIKA Project, corsika-project@lists.kit.edu
+ *
+ * See file AUTHORS for a list of contributors.
+ *
+ * This software is distributed under the terms of the GNU General Public
+ * Licence version 3 (GPL Version 3). See file LICENSE for a full version of
+ * the license.
+ */
+
+#include <filesystem>
+#include <string>
+
+namespace corsika::utl {
+  /**
+   * returns the full path of the file \p filename within the CORSIKA_DATA directory
+   */
+  std::filesystem::path CorsikaData(std::filesystem::path const& filename);
+} // namespace corsika::utl