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79 lines
2.1 KiB
79 lines
2.1 KiB
4 months ago
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/*
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* Copyright (C) 2020 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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#pragma once
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#include <condition_variable>
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#include <memory>
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#include <vector>
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#include "common/libs/concurrency/semaphore.h"
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#include "common/libs/concurrency/thread_safe_queue.h"
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namespace cuttlefish {
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namespace confui {
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template <typename T>
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class Multiplexer {
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public:
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Multiplexer(int n_qs, int max_elements) : sem_items_{0}, next_{0} {
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auto drop_new = [](typename ThreadSafeQueue<T>::QueueImpl* internal_q) {
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internal_q->pop_front();
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};
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for (int i = 0; i < n_qs; i++) {
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auto queue = std::make_unique<ThreadSafeQueue<T>>(max_elements, drop_new);
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queues_.push_back(std::move(queue));
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}
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}
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int GetNewQueueId() {
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CHECK(next_ < queues_.size())
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<< "can't get more queues than " << queues_.size();
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return next_++;
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}
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void Push(const int idx, T&& t) {
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CheckIdx(idx);
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queues_[idx]->Push(t);
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sem_items_.SemPost();
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}
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T Pop() {
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// the idx must have an item!
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// no waiting in fn()!
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sem_items_.SemWait();
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for (auto& q : queues_) {
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if (q->IsEmpty()) {
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continue;
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}
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return q->Pop();
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}
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CHECK(false) << "Multiplexer.Pop() should be able to return an item";
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// must not reach here
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return T{};
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}
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private:
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void CheckIdx(const int idx) {
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CHECK(idx >= 0 && idx < queues_.size()) << "queues_ array out of bound";
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}
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// total items across the queues
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Semaphore sem_items_;
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std::vector<std::unique_ptr<ThreadSafeQueue<T>>> queues_;
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int next_;
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};
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} // end of namespace confui
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} // end of namespace cuttlefish
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