1 /* 2 * Copyright (C) 2017 The Android Open Source Project 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 * http://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 #pragma once 18 19 namespace slicer { 20 21 // A simple and lightweight scope guard and macro 22 // (inspired by Andrei Alexandrescu's C++11 Scope Guard) 23 // 24 // Here is how it's used: 25 // 26 // FILE* file = std::fopen(...); 27 // SLICER_SCOPE_EXIT { 28 // std::fclose(file); 29 // }; 30 // 31 // "file" will be closed at the end of the enclosing scope, 32 // regardless of how the scope is exited 33 // 34 class ScopeGuardHelper 35 { 36 template<class T> 37 class ScopeGuard 38 { 39 public: ScopeGuard(T closure)40 explicit ScopeGuard(T closure) : 41 closure_(std::move(closure)) 42 { 43 } 44 ~ScopeGuard()45 ~ScopeGuard() 46 { 47 closure_(); 48 } 49 50 // move constructor only 51 ScopeGuard(ScopeGuard&&) = default; 52 ScopeGuard(const ScopeGuard&) = delete; 53 ScopeGuard& operator=(const ScopeGuard&) = delete; 54 ScopeGuard& operator=(ScopeGuard&&) = delete; 55 56 private: 57 T closure_; 58 }; 59 60 public: 61 template<class T> 62 ScopeGuard<T> operator<<(T closure) 63 { 64 return ScopeGuard<T>(std::move(closure)); 65 } 66 }; 67 68 #define SLICER_SG_MACRO_CONCAT2(a, b) a ## b 69 #define SLICER_SG_MACRO_CONCAT(a, b) SLICER_SG_MACRO_CONCAT2(a, b) 70 #define SLICER_SG_ANONYMOUS(prefix) SLICER_SG_MACRO_CONCAT(prefix, __COUNTER__) 71 72 #define SLICER_SCOPE_EXIT \ 73 auto SLICER_SG_ANONYMOUS(_scope_guard_) = slicer::ScopeGuardHelper() << [&]() 74 75 } // namespace slicer 76 77