Create FairBaseTypes.h

Created `namespace FairRoot`
with `struct EntryID {size_t fId;}`.

Should replace PR #1405.

fairroot/tools/CMakeLists.txt

@@ -20,6 +20,10 @@ set(sources
 
 fair_change_extensions_if_exists(.cxx .h FILES "${sources}" OUTVAR headers)
 
+list(APPEND headers
+  FairBaseTypes.h
+)
+
 add_library(${target} SHARED ${sources} ${headers})
 fairroot_library_settings(${target})
 # Keep old filesystem name

fairroot/tools/FairBaseTypes.h

@@ -0,0 +1,81 @@
+/********************************************************************************
+ * Copyright (C) 2014-2023 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH  *
+ *                                                                              *
+ *              This software is distributed under the terms of the             *
+ *              GNU Lesser General Public Licence (LGPL) version 3,             *
+ *                  copied verbatim in the file "LICENSE"                       *
+ ********************************************************************************/
+/*
+ * FairBaseTypes.h
+ *
+ *  Created on: May 16, 2023
+ *      Author: R.Karabowicz
+ */
+
+#ifndef FAIR_BASETYPES_H_
+#define FAIR_BASETYPES_H_
+
+#include <iostream>
+#include <limits>
+
+namespace FairRoot {
+    struct EntryID {
+        using underlying_type = size_t;
+
+        static constexpr underlying_type None = std::numeric_limits<underlying_type>::max();
+
+        EntryID(underlying_type value) : fId(value) {}
+
+        EntryID() : EntryID(None) {}
+
+        operator underlying_type() const { return fId; }
+
+        friend auto operator<<(std::ostream& os, EntryID id) -> std::ostream& {
+            if (id == None) {
+                return os << "<No Entry>";
+            }
+            return os << static_cast<underlying_type>(id);
+        }
+
+        auto operator++() {
+            if (fId != None) {
+                ++fId;
+            }
+            return *this;
+        }
+        auto operator++(int) {
+            auto temp = *this;
+            if (fId != None) {
+                ++fId;
+            }
+            return temp;
+        }
+
+        auto operator--() {
+            if (fId != None) {
+                --fId;
+            }
+            return *this;
+        }
+        auto operator--(int) {
+            auto temp = *this;
+            if (fId != None) {
+                --fId;
+            }
+            return temp;
+        }
+        auto operator+=(const EntryID& rhs) {
+            fId += rhs.fId;
+            return *this;
+        }
+        auto operator-=(const EntryID& rhs) {
+            fId -= rhs.fId;
+            return *this;
+        }
+
+    private:
+        underlying_type fId;
+    };
+}
+
+#endif   // FAIR_BASETYPES_H_