108 lines
3.1 KiB
C++
108 lines
3.1 KiB
C++
#pragma once
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/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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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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#include <condition_variable>
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#include <deque>
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#include <iterator>
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#include <mutex>
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#include <type_traits>
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#include <utility>
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namespace cuttlefish {
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// Simple queue with Push and Pop capabilities.
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// If the max_elements argument is passed to the constructor, and Push is called
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// when the queue holds max_elements items, the max_elements_handler is called
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// with a pointer to the internal QueueImpl. The call is made while holding
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// the guarding mutex; operations on the QueueImpl will not interleave with
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// other threads calling Push() or Pop().
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// The QueueImpl type will be a SequenceContainer.
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template <typename T>
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class ThreadSafeQueue {
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public:
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using QueueImpl = std::deque<T>;
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using QueueFullHandler = std::function<void(QueueImpl*)>;
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ThreadSafeQueue() = default;
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explicit ThreadSafeQueue(std::size_t max_elements,
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QueueFullHandler max_elements_handler)
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: max_elements_{max_elements},
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max_elements_handler_{std::move(max_elements_handler)} {}
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T Pop() {
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std::unique_lock<std::mutex> guard(m_);
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while (items_.empty()) {
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new_item_.wait(guard);
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}
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auto t = std::move(items_.front());
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items_.pop_front();
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return t;
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}
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QueueImpl PopAll() {
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std::unique_lock<std::mutex> guard(m_);
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while (items_.empty()) {
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new_item_.wait(guard);
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}
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return std::move(items_);
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}
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template <typename U>
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bool Push(U&& u) {
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static_assert(std::is_assignable_v<T, decltype(u)>);
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std::lock_guard<std::mutex> guard(m_);
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const bool has_room = DropItemsIfAtCapacity();
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if (!has_room) {
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return false;
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}
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items_.push_back(std::forward<U>(u));
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new_item_.notify_one();
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return true;
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}
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bool IsEmpty() {
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std::lock_guard<std::mutex> guard(m_);
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return items_.empty();
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}
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bool IsFull() {
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std::lock_guard<std::mutex> guard(m_);
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return items_.size() == max_elements_;
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}
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private:
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// return whether there's room to push
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bool DropItemsIfAtCapacity() {
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if (max_elements_ && max_elements_ == items_.size()) {
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max_elements_handler_(&items_);
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}
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if (max_elements_ && max_elements_ == items_.size()) {
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// handler intends to ignore the newly coming element or
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// did not empty the room for whatever reason
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return false;
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}
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return true;
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}
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std::mutex m_;
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std::size_t max_elements_{};
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QueueFullHandler max_elements_handler_{};
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std::condition_variable new_item_;
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QueueImpl items_;
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};
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} // namespace cuttlefish
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