139 lines
3.9 KiB
C++
139 lines
3.9 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License Version 2.0 with LLVM Exceptions
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* https://llvm.org/LICENSE.txt
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <unifex/detail/atomic_intrusive_queue.hpp>
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#include <unifex/detail/intrusive_queue.hpp>
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#include <unifex/receiver_concepts.hpp>
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#include <unifex/sender_concepts.hpp>
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#include <unifex/tag_invoke.hpp>
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#include <unifex/detail/prologue.hpp>
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namespace unifex {
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class async_mutex {
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class lock_sender;
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public:
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async_mutex() noexcept;
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async_mutex(const async_mutex &) = delete;
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async_mutex(async_mutex &&) = delete;
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~async_mutex();
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async_mutex &operator=(const async_mutex &) = delete;
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async_mutex &operator=(async_mutex &&) = delete;
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[[nodiscard]] bool try_lock() noexcept;
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[[nodiscard]] lock_sender async_lock() noexcept;
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void unlock() noexcept;
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private:
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struct waiter_base {
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void (*resume_)(waiter_base *) noexcept;
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waiter_base *next_;
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};
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class lock_sender {
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public:
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template <template <typename...> class Variant,
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template <typename...> class Tuple>
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using value_types = Variant<Tuple<>>;
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template <template <typename...> class Variant>
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using error_types = Variant<>;
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static constexpr bool sends_done = false;
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lock_sender(const lock_sender &) = delete;
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lock_sender(lock_sender &&) = default;
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private:
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friend async_mutex;
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explicit lock_sender(async_mutex &mutex) noexcept
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: mutex_(mutex) {}
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template <typename Receiver>
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struct _op {
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class type : waiter_base {
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friend lock_sender;
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public:
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template <typename Receiver2>
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explicit type(async_mutex &mutex, Receiver2 &&r) noexcept
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: mutex_(mutex), receiver_((Receiver2 &&) r) {
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this->resume_ = [](waiter_base * self) noexcept {
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type &op = *static_cast<type *>(self);
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unifex::set_value((Receiver &&) op.receiver_);
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};
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}
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type(type &&) = delete;
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private:
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friend void tag_invoke(tag_t<start>, type &op) noexcept {
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if (!op.try_enqueue()) {
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// Failed to enqueue because we acquired the lock
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// synchronously. Invoke the continuation inline
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// without type-erasure here.
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set_value((Receiver &&) op.receiver_);
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}
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}
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bool try_enqueue() noexcept {
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return mutex_.try_enqueue(this);
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}
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async_mutex &mutex_;
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Receiver receiver_;
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};
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};
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template <typename Receiver>
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using operation = typename _op<remove_cvref_t<Receiver>>::type;
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template(typename Receiver)
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(requires receiver<Receiver>)
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friend operation<Receiver>
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tag_invoke(tag_t<connect>, lock_sender &&s, Receiver &&r) noexcept {
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return operation<Receiver>{s.mutex_, (Receiver &&) r};
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}
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async_mutex &mutex_;
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};
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// Attempt to enqueue the waiter object to the queue.
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// Returns true if successfully enqueued, false if it was not enqueued because
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// the lock was acquired synchronously.
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bool try_enqueue(waiter_base *waiter) noexcept;
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atomic_intrusive_queue<waiter_base, &waiter_base::next_> atomicQueue_;
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intrusive_queue<waiter_base, &waiter_base::next_> pendingQueue_;
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};
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inline async_mutex::lock_sender async_mutex::async_lock() noexcept {
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return lock_sender{*this};
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}
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inline bool async_mutex::try_lock() noexcept {
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return atomicQueue_.try_mark_active();
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}
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} // namespace unifex
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#include <unifex/detail/epilogue.hpp>
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