Import Geant4 11.3.0 source tree

source/externals/ptl/include/PTL/GetEnv.hh

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+//
+// MIT License
+// Copyright (c) 2020 Jonathan R. Madsen
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED
+// "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
+// LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+//
+
+#pragma once
+
+#include <cctype>
+#include <cstdlib>
+#include <functional>
+#include <iomanip>
+#include <iostream>
+#include <map>
+#include <mutex>
+#include <set>
+#include <sstream>  // IWYU pragma: keep
+#include <string>
+#include <tuple>
+#include <utility>
+
+namespace PTL
+{
+//--------------------------------------------------------------------------------------//
+//  use this function to get an environment variable setting +
+//  a default if not defined, e.g.
+//      int num_threads =
+//          GetEnv<int>("FORCENUMBEROFTHREADS",
+//                          std::thread::hardware_concurrency());
+//
+template <typename Tp>
+Tp
+GetEnv(const std::string& env_id, Tp _default = Tp())
+{
+    char* env_var = std::getenv(env_id.c_str());
+    if(env_var)
+    {
+        std::string        str_var = std::string(env_var);
+        std::istringstream iss(str_var);
+        Tp                 var = Tp();
+        iss >> var;
+        return var;
+    }
+
+    // return default if not specified in environment
+    return _default;
+}
+
+//--------------------------------------------------------------------------------------//
+//  overload for boolean
+//
+template <>
+inline bool
+GetEnv(const std::string& env_id, bool _default)
+{
+    char* env_var = std::getenv(env_id.c_str());
+    if(env_var)
+    {
+        std::string var = std::string(env_var);
+        bool        val = true;
+        if(var.find_first_not_of("0123456789") == std::string::npos)
+            val = (bool) atoi(var.c_str());
+        else
+        {
+            for(auto& itr : var)
+                itr = tolower(itr);
+            if(var == "off" || var == "false")
+                val = false;
+        }
+        return val;
+    }
+
+    // return default if not specified in environment
+    return _default;
+}
+
+//--------------------------------------------------------------------------------------//
+
+}  // namespace PTL