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File indexing completed on 2025-09-17 08:54:09
0001 //------------------------------- -*- C++ -*- -------------------------------// 0002 // Copyright Celeritas contributors: see top-level COPYRIGHT file for details 0003 // SPDX-License-Identifier: (Apache-2.0 OR MIT) 0004 //---------------------------------------------------------------------------// 0005 //! \file corecel/sys/Environment.hh 0006 //---------------------------------------------------------------------------// 0007 #pragma once 0008 0009 #include <functional> 0010 #include <iosfwd> 0011 #include <string> 0012 #include <unordered_map> 0013 #include <utility> 0014 #include <vector> 0015 0016 namespace celeritas 0017 { 0018 //---------------------------------------------------------------------------// 0019 /*! 0020 * Interrogate and extend environment variables. 0021 * 0022 * This makes it easier to generate reproducible runs, launch Celeritas 0023 * remotely, or integrate with application drivers. The environment variables 0024 * may be encoded as JSON input to supplement or override system environment 0025 * variables, or set programmatically via this API call. Later the environment 0026 * class can be interrogated to find which environment variables were accessed. 0027 * 0028 * Unlike the standard environment which returns a null pointer for an *unset* 0029 * variable, this returns an empty string. 0030 * 0031 * \note This class is not thread-safe on its own. The \c celeritas::getenv 0032 * free function however is safe, although it should only be used in setup 0033 * (single-thread) steps. 0034 * 0035 * \note Once inserted into the environment map, values cannot be changed. 0036 * Standard practice in the code is to evaluate the environment variable 0037 * exactly \em once and cache the result as a static const variable. If you 0038 * really wanted to, you could call <code> celeritas::environment() = {}; 0039 * </code> but that could result in the end-of-run diagnostic reporting 0040 * different values than the ones actually used during the code's setup. 0041 */ 0042 class Environment 0043 { 0044 private: 0045 using Container = std::unordered_map<std::string, std::string>; 0046 0047 public: 0048 //!@{ 0049 //! \name Type aliases 0050 using key_type = Container::key_type; 0051 using mapped_type = Container::mapped_type; 0052 using value_type = Container::value_type; 0053 using const_iterator = Container::const_iterator; 0054 using VecKVRef = std::vector<std::reference_wrapper<value_type>>; 0055 //!@} 0056 0057 public: 0058 // Construct with defaults 0059 Environment() = default; 0060 0061 // Get an environment variable from current or system environments 0062 inline mapped_type const& operator[](key_type const&); 0063 0064 // Insert possibly new environment variables 0065 bool insert(value_type const& value); 0066 0067 //! Get an ordered (by access) vector of key/value pairs 0068 VecKVRef const& ordered_environment() const { return ordered_; } 0069 0070 // Remove all entries 0071 void clear(); 0072 0073 // Insert (not overriding!) from another environment 0074 void merge(Environment const& other); 0075 0076 //!@{ 0077 //! Access all entries, unordered, by const iterator 0078 const_iterator begin() const { return vars_.cbegin(); } 0079 const_iterator cbegin() const { return vars_.cbegin(); } 0080 const_iterator end() const { return vars_.cend(); } 0081 const_iterator cend() const { return vars_.cend(); } 0082 //!@} 0083 0084 private: 0085 std::unordered_map<key_type, mapped_type> vars_; 0086 VecKVRef ordered_; 0087 0088 mapped_type const& load_from_getenv(key_type const&); 0089 }; 0090 0091 //---------------------------------------------------------------------------// 0092 //! Return result from \c getenv_flag 0093 struct GetenvFlagResult 0094 { 0095 bool value{}; //!< Determined by user or default 0096 bool defaulted{}; //!< True if no valid user value was present 0097 }; 0098 0099 //---------------------------------------------------------------------------// 0100 // FREE FUNCTIONS 0101 //---------------------------------------------------------------------------// 0102 0103 // Access a static global environment variable 0104 Environment& environment(); 0105 0106 // Thread-safe access to environment variables 0107 std::string const& getenv(std::string const& key); 0108 0109 // Thread-safe flag access to environment variables 0110 GetenvFlagResult getenv_flag(std::string const& key, bool default_val); 0111 0112 // Write the accessed environment variables to a stream 0113 std::ostream& operator<<(std::ostream&, Environment const&); 0114 0115 //---------------------------------------------------------------------------// 0116 // INLINE DEFINITIONS 0117 //---------------------------------------------------------------------------// 0118 /*! 0119 * Get an environment variable from current or system enviroments. 0120 */ 0121 auto Environment::operator[](key_type const& env_var) -> mapped_type const& 0122 { 0123 auto iter = vars_.find(env_var); 0124 if (iter == vars_.end()) 0125 { 0126 return this->load_from_getenv(env_var); 0127 } 0128 return iter->second; 0129 } 0130 0131 //---------------------------------------------------------------------------// 0132 } // namespace celeritas
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