| /* |
| * |
| * Copyright 2017 gRPC 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 |
| * |
| * http://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. |
| * |
| */ |
| |
| #ifndef GRPC_CORE_LIB_GPRPP_ATOMIC_H |
| #define GRPC_CORE_LIB_GPRPP_ATOMIC_H |
| |
| #include <grpc/support/port_platform.h> |
| |
| #include <atomic> |
| |
| #include <grpc/support/atm.h> |
| |
| namespace grpc_core { |
| |
| enum class MemoryOrder { |
| RELAXED = static_cast<int>(std::memory_order_relaxed), |
| CONSUME = static_cast<int>(std::memory_order_consume), |
| ACQUIRE = static_cast<int>(std::memory_order_acquire), |
| RELEASE = static_cast<int>(std::memory_order_release), |
| ACQ_REL = static_cast<int>(std::memory_order_acq_rel), |
| SEQ_CST = static_cast<int>(std::memory_order_seq_cst) |
| }; |
| |
| template <typename T> |
| class Atomic { |
| public: |
| explicit Atomic(T val = T()) : storage_(val) {} |
| |
| T Load(MemoryOrder order) const { |
| return storage_.load(static_cast<std::memory_order>(order)); |
| } |
| |
| void Store(T val, MemoryOrder order) { |
| storage_.store(val, static_cast<std::memory_order>(order)); |
| } |
| |
| T Exchange(T desired, MemoryOrder order) { |
| return storage_.exchange(desired, static_cast<std::memory_order>(order)); |
| } |
| |
| bool CompareExchangeWeak(T* expected, T desired, MemoryOrder success, |
| MemoryOrder failure) { |
| return GPR_ATM_INC_CAS_THEN(storage_.compare_exchange_weak( |
| *expected, desired, static_cast<std::memory_order>(success), |
| static_cast<std::memory_order>(failure))); |
| } |
| |
| bool CompareExchangeStrong(T* expected, T desired, MemoryOrder success, |
| MemoryOrder failure) { |
| return GPR_ATM_INC_CAS_THEN(storage_.compare_exchange_strong( |
| *expected, desired, static_cast<std::memory_order>(success), |
| static_cast<std::memory_order>(failure))); |
| } |
| |
| template <typename Arg> |
| T FetchAdd(Arg arg, MemoryOrder order = MemoryOrder::SEQ_CST) { |
| return GPR_ATM_INC_ADD_THEN(storage_.fetch_add( |
| static_cast<Arg>(arg), static_cast<std::memory_order>(order))); |
| } |
| |
| template <typename Arg> |
| T FetchSub(Arg arg, MemoryOrder order = MemoryOrder::SEQ_CST) { |
| return GPR_ATM_INC_ADD_THEN(storage_.fetch_sub( |
| static_cast<Arg>(arg), static_cast<std::memory_order>(order))); |
| } |
| |
| // Atomically increment a counter only if the counter value is not zero. |
| // Returns true if increment took place; false if counter is zero. |
| bool IncrementIfNonzero(MemoryOrder load_order = MemoryOrder::ACQUIRE) { |
| T count = storage_.load(static_cast<std::memory_order>(load_order)); |
| do { |
| // If zero, we are done (without an increment). If not, we must do a CAS |
| // to maintain the contract: do not increment the counter if it is already |
| // zero |
| if (count == 0) { |
| return false; |
| } |
| } while (!CompareExchangeWeak(&count, count + 1, MemoryOrder::ACQ_REL, |
| load_order)); |
| return true; |
| } |
| |
| private: |
| std::atomic<T> storage_; |
| }; |
| |
| } // namespace grpc_core |
| |
| #endif /* GRPC_CORE_LIB_GPRPP_ATOMIC_H */ |