reflection.h (2883B)
1 // 2 // Copyright 2020 The Abseil Authors. 3 // 4 // Licensed under the Apache License, Version 2.0 (the "License"); 5 // you may not use this file except in compliance with the License. 6 // You may obtain a copy of the License at 7 // 8 // https://www.apache.org/licenses/LICENSE-2.0 9 // 10 // Unless required by applicable law or agreed to in writing, software 11 // distributed under the License is distributed on an "AS IS" BASIS, 12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 // See the License for the specific language governing permissions and 14 // limitations under the License. 15 // 16 // ----------------------------------------------------------------------------- 17 // File: reflection.h 18 // ----------------------------------------------------------------------------- 19 // 20 // This file defines the routines to access and operate on an Abseil Flag's 21 // reflection handle. 22 23 #ifndef ABSL_FLAGS_REFLECTION_H_ 24 #define ABSL_FLAGS_REFLECTION_H_ 25 26 #include <string> 27 28 #include "absl/base/config.h" 29 #include "absl/container/flat_hash_map.h" 30 #include "absl/flags/commandlineflag.h" 31 #include "absl/flags/internal/commandlineflag.h" 32 33 namespace absl { 34 ABSL_NAMESPACE_BEGIN 35 namespace flags_internal { 36 class FlagSaverImpl; 37 } // namespace flags_internal 38 39 // FindCommandLineFlag() 40 // 41 // Returns the reflection handle of an Abseil flag of the specified name, or 42 // `nullptr` if not found. This function will emit a warning if the name of a 43 // 'retired' flag is specified. 44 absl::CommandLineFlag* FindCommandLineFlag(absl::string_view name); 45 46 // Returns current state of the Flags registry in a form of mapping from flag 47 // name to a flag reflection handle. 48 absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags(); 49 50 //------------------------------------------------------------------------------ 51 // FlagSaver 52 //------------------------------------------------------------------------------ 53 // 54 // A FlagSaver object stores the state of flags in the scope where the FlagSaver 55 // is defined, allowing modification of those flags within that scope and 56 // automatic restoration of the flags to their previous state upon leaving the 57 // scope. 58 // 59 // A FlagSaver can be used within tests to temporarily change the test 60 // environment and restore the test case to its previous state. 61 // 62 // Example: 63 // 64 // void MyFunc() { 65 // absl::FlagSaver fs; 66 // ... 67 // absl::SetFlag(&FLAGS_myFlag, otherValue); 68 // ... 69 // } // scope of FlagSaver left, flags return to previous state 70 // 71 // This class is thread-safe. 72 73 class FlagSaver { 74 public: 75 FlagSaver(); 76 ~FlagSaver(); 77 78 FlagSaver(const FlagSaver&) = delete; 79 void operator=(const FlagSaver&) = delete; 80 81 private: 82 flags_internal::FlagSaverImpl* impl_; 83 }; 84 85 //----------------------------------------------------------------------------- 86 87 ABSL_NAMESPACE_END 88 } // namespace absl 89 90 #endif // ABSL_FLAGS_REFLECTION_H_