| 1 | /* |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * This source code is licensed under both the BSD-style license (found in the |
| 6 | * LICENSE file in the root directory of this source tree) and the GPLv2 (found |
| 7 | * in the COPYING file in the root directory of this source tree). |
| 8 | */ |
| 9 | #pragma once |
| 10 | |
| 11 | #include "utils/Buffer.h" |
| 12 | |
| 13 | #include <atomic> |
| 14 | #include <cassert> |
| 15 | #include <cstddef> |
| 16 | #include <condition_variable> |
| 17 | #include <cstddef> |
| 18 | #include <functional> |
| 19 | #include <mutex> |
| 20 | #include <queue> |
| 21 | |
| 22 | namespace pzstd { |
| 23 | |
| 24 | /// Unbounded thread-safe work queue. |
| 25 | template <typename T> |
| 26 | class WorkQueue { |
| 27 | // Protects all member variable access |
| 28 | std::mutex mutex_; |
| 29 | std::condition_variable readerCv_; |
| 30 | std::condition_variable writerCv_; |
| 31 | std::condition_variable finishCv_; |
| 32 | |
| 33 | std::queue<T> queue_; |
| 34 | bool done_; |
| 35 | std::size_t maxSize_; |
| 36 | |
| 37 | // Must have lock to call this function |
| 38 | bool full() const { |
| 39 | if (maxSize_ == 0) { |
| 40 | return false; |
| 41 | } |
| 42 | return queue_.size() >= maxSize_; |
| 43 | } |
| 44 | |
| 45 | public: |
| 46 | /** |
| 47 | * Constructs an empty work queue with an optional max size. |
| 48 | * If `maxSize == 0` the queue size is unbounded. |
| 49 | * |
| 50 | * @param maxSize The maximum allowed size of the work queue. |
| 51 | */ |
| 52 | WorkQueue(std::size_t maxSize = 0) : done_(false), maxSize_(maxSize) {} |
| 53 | |
| 54 | /** |
| 55 | * Push an item onto the work queue. Notify a single thread that work is |
| 56 | * available. If `finish()` has been called, do nothing and return false. |
| 57 | * If `push()` returns false, then `item` has not been moved from. |
| 58 | * |
| 59 | * @param item Item to push onto the queue. |
| 60 | * @returns True upon success, false if `finish()` has been called. An |
| 61 | * item was pushed iff `push()` returns true. |
| 62 | */ |
| 63 | bool push(T&& item) { |
| 64 | { |
| 65 | std::unique_lock<std::mutex> lock(mutex_); |
| 66 | while (full() && !done_) { |
| 67 | writerCv_.wait(lock); |
| 68 | } |
| 69 | if (done_) { |
| 70 | return false; |
| 71 | } |
| 72 | queue_.push(std::move(item)); |
| 73 | } |
| 74 | readerCv_.notify_one(); |
| 75 | return true; |
| 76 | } |
| 77 | |
| 78 | /** |
| 79 | * Attempts to pop an item off the work queue. It will block until data is |
| 80 | * available or `finish()` has been called. |
| 81 | * |
| 82 | * @param[out] item If `pop` returns `true`, it contains the popped item. |
| 83 | * If `pop` returns `false`, it is unmodified. |
| 84 | * @returns True upon success. False if the queue is empty and |
| 85 | * `finish()` has been called. |
| 86 | */ |
| 87 | bool pop(T& item) { |
| 88 | { |
| 89 | std::unique_lock<std::mutex> lock(mutex_); |
| 90 | while (queue_.empty() && !done_) { |
| 91 | readerCv_.wait(lock); |
| 92 | } |
| 93 | if (queue_.empty()) { |
| 94 | assert(done_); |
| 95 | return false; |
| 96 | } |
| 97 | item = std::move(queue_.front()); |
| 98 | queue_.pop(); |
| 99 | } |
| 100 | writerCv_.notify_one(); |
| 101 | return true; |
| 102 | } |
| 103 | |
| 104 | /** |
| 105 | * Sets the maximum queue size. If `maxSize == 0` then it is unbounded. |
| 106 | * |
| 107 | * @param maxSize The new maximum queue size. |
| 108 | */ |
| 109 | void setMaxSize(std::size_t maxSize) { |
| 110 | { |
| 111 | std::lock_guard<std::mutex> lock(mutex_); |
| 112 | maxSize_ = maxSize; |
| 113 | } |
| 114 | writerCv_.notify_all(); |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * Promise that `push()` won't be called again, so once the queue is empty |
| 119 | * there will never any more work. |
| 120 | */ |
| 121 | void finish() { |
| 122 | { |
| 123 | std::lock_guard<std::mutex> lock(mutex_); |
| 124 | assert(!done_); |
| 125 | done_ = true; |
| 126 | } |
| 127 | readerCv_.notify_all(); |
| 128 | writerCv_.notify_all(); |
| 129 | finishCv_.notify_all(); |
| 130 | } |
| 131 | |
| 132 | /// Blocks until `finish()` has been called (but the queue may not be empty). |
| 133 | void waitUntilFinished() { |
| 134 | std::unique_lock<std::mutex> lock(mutex_); |
| 135 | while (!done_) { |
| 136 | finishCv_.wait(lock); |
| 137 | } |
| 138 | } |
| 139 | }; |
| 140 | |
| 141 | /// Work queue for `Buffer`s that knows the total number of bytes in the queue. |
| 142 | class BufferWorkQueue { |
| 143 | WorkQueue<Buffer> queue_; |
| 144 | std::atomic<std::size_t> size_; |
| 145 | |
| 146 | public: |
| 147 | BufferWorkQueue(std::size_t maxSize = 0) : queue_(maxSize), size_(0) {} |
| 148 | |
| 149 | void push(Buffer buffer) { |
| 150 | size_.fetch_add(buffer.size()); |
| 151 | queue_.push(std::move(buffer)); |
| 152 | } |
| 153 | |
| 154 | bool pop(Buffer& buffer) { |
| 155 | bool result = queue_.pop(buffer); |
| 156 | if (result) { |
| 157 | size_.fetch_sub(buffer.size()); |
| 158 | } |
| 159 | return result; |
| 160 | } |
| 161 | |
| 162 | void setMaxSize(std::size_t maxSize) { |
| 163 | queue_.setMaxSize(maxSize); |
| 164 | } |
| 165 | |
| 166 | void finish() { |
| 167 | queue_.finish(); |
| 168 | } |
| 169 | |
| 170 | /** |
| 171 | * Blocks until `finish()` has been called. |
| 172 | * |
| 173 | * @returns The total number of bytes of all the `Buffer`s currently in the |
| 174 | * queue. |
| 175 | */ |
| 176 | std::size_t size() { |
| 177 | queue_.waitUntilFinished(); |
| 178 | return size_.load(); |
| 179 | } |
| 180 | }; |
| 181 | } |