1/*
2 * Copyright 2017-present Facebook, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#pragma once
18
19#include <folly/MPMCQueue.h>
20#include <folly/executors/task_queue/BlockingQueue.h>
21#include <folly/synchronization/LifoSem.h>
22
23namespace folly {
24
25template <class T, QueueBehaviorIfFull kBehavior = QueueBehaviorIfFull::THROW>
26class LifoSemMPMCQueue : public BlockingQueue<T> {
27 public:
28 // Note: The queue pre-allocates all memory for max_capacity
29 explicit LifoSemMPMCQueue(size_t max_capacity) : queue_(max_capacity) {}
30
31 BlockingQueueAddResult add(T item) override {
32 switch (kBehavior) { // static
33 case QueueBehaviorIfFull::THROW:
34 if (!queue_.write(std::move(item))) {
35 throw QueueFullException("LifoSemMPMCQueue full, can't add item");
36 }
37 break;
38 case QueueBehaviorIfFull::BLOCK:
39 queue_.blockingWrite(std::move(item));
40 break;
41 }
42 return sem_.post();
43 }
44
45 T take() override {
46 T item;
47 while (!queue_.readIfNotEmpty(item)) {
48 sem_.wait();
49 }
50 return item;
51 }
52
53 folly::Optional<T> try_take_for(std::chrono::milliseconds time) override {
54 T item;
55 while (!queue_.readIfNotEmpty(item)) {
56 if (!sem_.try_wait_for(time)) {
57 return folly::none;
58 }
59 }
60 return std::move(item);
61 }
62
63 size_t capacity() {
64 return queue_.capacity();
65 }
66
67 size_t size() override {
68 return queue_.size();
69 }
70
71 private:
72 folly::LifoSem sem_;
73 folly::MPMCQueue<T> queue_;
74};
75
76} // namespace folly
77