| // Copyright 2021 The Abseil Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| // |
| // ----------------------------------------------------------------------------- |
| // File: cleanup.h |
| // ----------------------------------------------------------------------------- |
| // |
| // `absl::Cleanup` implements the scope guard idiom, invoking `operator()() &&` |
| // on the callback it was constructed with, on scope exit. |
| // |
| // Example: |
| // |
| // ``` |
| // void CopyGoodData(const char* input_path, const char* output_path) { |
| // FILE* in_file = fopen(input_path, "r"); |
| // FILE* out_file = fopen(output_path, "w"); |
| // if (in_file == nullptr || out_file == nullptr) return; |
| // |
| // // C++17 style using class template argument deduction |
| // absl::Cleanup in_closer = [&in_file] { fclose(in_file); }; |
| // |
| // // C++11 style using the factory function |
| // auto out_closer = absl::MakeCleanup([&out_file] { fclose(out_file); }); |
| // |
| // // `fclose` will be called on all exit paths by the cleanup instances |
| // |
| // Data data; |
| // while (ReadData(in_file, &data)) { |
| // if (data.IsBad()) { |
| // LOG(ERROR) << "Found bad data."; |
| // return; // `in_closer` and `out_closer` will call their callbacks |
| // } |
| // SaveData(out_file, &data); |
| // } |
| // return; // `in_closer` and `out_closer` will call their callbacks |
| // } |
| // ``` |
| // |
| // `std::move(cleanup).Invoke()` will execute the callback early, before |
| // destruction, and prevent the callback from executing in the destructor. |
| // |
| // Alternatively, `std::move(cleanup).Cancel()` will prevent the callback from |
| // ever executing at all. |
| // |
| // Once a cleanup object has been `std::move(...)`-ed, it may not be used again. |
| |
| #ifndef ABSL_CLEANUP_CLEANUP_H_ |
| #define ABSL_CLEANUP_CLEANUP_H_ |
| |
| #include <utility> |
| |
| #include "absl/base/config.h" |
| #include "absl/base/macros.h" |
| #include "absl/cleanup/internal/cleanup.h" |
| |
| namespace absl { |
| ABSL_NAMESPACE_BEGIN |
| |
| template <typename Arg, typename Callback = void()> |
| class ABSL_MUST_USE_RESULT Cleanup { |
| static_assert(cleanup_internal::WasDeduced<Arg>(), |
| "Explicit template parameters are not supported."); |
| |
| static_assert(cleanup_internal::ReturnsVoid<Callback>(), |
| "Callbacks that return values are not supported."); |
| |
| public: |
| Cleanup(Callback callback) : storage_(std::move(callback)) {} // NOLINT |
| |
| Cleanup(Cleanup&& other) : storage_(std::move(other.storage_)) {} |
| |
| void Cancel() && { |
| ABSL_HARDENING_ASSERT(storage_.IsCallbackEngaged()); |
| storage_.DisengageCallback(); |
| } |
| |
| void Invoke() && { |
| ABSL_HARDENING_ASSERT(storage_.IsCallbackEngaged()); |
| storage_.DisengageCallback(); |
| storage_.InvokeCallback(); |
| } |
| |
| ~Cleanup() { |
| if (storage_.IsCallbackEngaged()) { |
| storage_.InvokeCallback(); |
| } |
| } |
| |
| private: |
| cleanup_internal::Storage<Callback> storage_; |
| }; |
| |
| // `auto c = absl::MakeCleanup(/* callback */);` |
| // |
| // C++11 type deduction API for creating an instance of `absl::Cleanup`. |
| template <typename... Args, typename Callback> |
| absl::Cleanup<cleanup_internal::Tag, Callback> MakeCleanup(Callback callback) { |
| static_assert(cleanup_internal::WasDeduced<cleanup_internal::Tag, Args...>(), |
| "Explicit template parameters are not supported."); |
| |
| static_assert(cleanup_internal::ReturnsVoid<Callback>(), |
| "Callbacks that return values are not supported."); |
| |
| return {std::move(callback)}; |
| } |
| |
| // `absl::Cleanup c = /* callback */;` |
| // |
| // C++17 type deduction API for creating an instance of `absl::Cleanup`. |
| #if defined(ABSL_HAVE_CLASS_TEMPLATE_ARGUMENT_DEDUCTION) |
| template <typename Callback> |
| Cleanup(Callback callback) -> Cleanup<cleanup_internal::Tag, Callback>; |
| #endif // defined(ABSL_HAVE_CLASS_TEMPLATE_ARGUMENT_DEDUCTION) |
| |
| ABSL_NAMESPACE_END |
| } // namespace absl |
| |
| #endif // ABSL_CLEANUP_CLEANUP_H_ |