\u4ee5 WebRTC library \u4e3a\u4f8b\uff0c\u8fd9\u4e24\u767e\u884c\u4ee3\u7801\u6f14\u793a\u4e86\u7ebf\u7a0b\u5207\u6362\u7684\u7ecf\u5178\u6a21\u5f0f\u3002<\/p>\n
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\n\/*\n * Copyright 2018 The WebRTC Project Authors. All rights reserved.\n *\n * Use of this source code is governed by a BSD-style license\n * that can be found in the LICENSE file in the root of the source\n * tree. An additional intellectual property rights grant can be found\n * in the file PATENTS. All contributing project authors may\n * be found in the AUTHORS file in the root of the source tree.\n *\/\n\n#include "rtc_base\/task_queue_stdlib.h"\n\n#include <string.h>\n\n#include <algorithm>\n#include <map>\n#include <memory>\n#include <queue>\n#include <utility>\n\n#include "absl\/strings\/string_view.h"\n#include "api\/task_queue\/queued_task.h"\n#include "api\/task_queue\/task_queue_base.h"\n#include "rtc_base\/checks.h"\n#include "rtc_base\/event.h"\n#include "rtc_base\/logging.h"\n#include "rtc_base\/platform_thread.h"\n#include "rtc_base\/synchronization\/mutex.h"\n#include "rtc_base\/thread_annotations.h"\n#include "rtc_base\/time_utils.h"\n\nnamespace webrtc {\nnamespace {\n\nrtc::ThreadPriority TaskQueuePriorityToThreadPriority(\n TaskQueueFactory::Priority priority) {\n switch (priority) {\n case TaskQueueFactory::Priority::HIGH:\n return rtc::ThreadPriority::kRealtime;\n case TaskQueueFactory::Priority::LOW:\n return rtc::ThreadPriority::kLow;\n case TaskQueueFactory::Priority::NORMAL:\n return rtc::ThreadPriority::kNormal;\n }\n}\n\nclass TaskQueueStdlib final : public TaskQueueBase {\n public:\n TaskQueueStdlib(absl::string_view queue_name, rtc::ThreadPriority priority);\n ~TaskQueueStdlib() override = default;\n\n void Delete() override;\n void PostTask(std::unique_ptr<QueuedTask> task) override;\n void PostDelayedTask(std::unique_ptr<QueuedTask> task,\n uint32_t milliseconds) override;\n\n private:\n using OrderId = uint64_t;\n\n struct DelayedEntryTimeout {\n int64_t next_fire_at_ms_{};\n OrderId order_{};\n\n bool operator<(const DelayedEntryTimeout& o) const {\n return std::tie(next_fire_at_ms_, order_) <\n std::tie(o.next_fire_at_ms_, o.order_);\n }\n };\n\n struct NextTask {\n bool final_task_{false};\n std::unique_ptr<QueuedTask> run_task_;\n int64_t sleep_time_ms_{};\n };\n\n NextTask GetNextTask();\n\n void ProcessTasks();\n\n void NotifyWake();\n\n \/\/ Indicates if the thread has started.\n rtc::Event started_;\n\n \/\/ Signaled whenever a new task is pending.\n rtc::Event flag_notify_;\n\n Mutex pending_lock_;\n\n \/\/ Indicates if the worker thread needs to shutdown now.\n bool thread_should_quit_ RTC_GUARDED_BY(pending_lock_){false};\n\n \/\/ Holds the next order to use for the next task to be\n \/\/ put into one of the pending queues.\n OrderId thread_posting_order_ RTC_GUARDED_BY(pending_lock_){};\n\n \/\/ The list of all pending tasks that need to be processed in the\n \/\/ FIFO queue ordering on the worker thread.\n std::queue<std::pair<OrderId, std::unique_ptr<QueuedTask>>> pending_queue_\n RTC_GUARDED_BY(pending_lock_);\n\n \/\/ The list of all pending tasks that need to be processed at a future\n \/\/ time based upon a delay. On the off change the delayed task should\n \/\/ happen at exactly the same time interval as another task then the\n \/\/ task is processed based on FIFO ordering. std::priority_queue was\n \/\/ considered but rejected due to its inability to extract the\n \/\/ std::unique_ptr out of the queue without the presence of a hack.\n std::map<DelayedEntryTimeout, std::unique_ptr<QueuedTask>> delayed_queue_\n RTC_GUARDED_BY(pending_lock_);\n\n \/\/ Contains the active worker thread assigned to processing\n \/\/ tasks (including delayed tasks).\n \/\/ Placing this last ensures the thread doesn't touch uninitialized attributes\n \/\/ throughout it's lifetime.\n rtc::PlatformThread thread_;\n};\n\nTaskQueueStdlib::TaskQueueStdlib(absl::string_view queue_name,\n rtc::ThreadPriority priority)\n : started_(\/*manual_reset=*\/false, \/*initially_signaled=*\/false),\n flag_notify_(\/*manual_reset=*\/false, \/*initially_signaled=*\/false),\n thread_(rtc::PlatformThread::SpawnJoinable(\n [this] {\n CurrentTaskQueueSetter set_current(this);\n ProcessTasks();\n },\n queue_name,\n rtc::ThreadAttributes().SetPriority(priority))) {\n started_.Wait(rtc::Event::kForever);\n}\n\nvoid TaskQueueStdlib::Delete() {\n RTC_DCHECK(!IsCurrent());\n\n {\n MutexLock lock(&pending_lock_);\n thread_should_quit_ = true;\n }\n\n NotifyWake();\n\n delete this;\n}\n\nvoid TaskQueueStdlib::PostTask(std::unique_ptr<QueuedTask> task) {\n {\n MutexLock lock(&pending_lock_);\n OrderId order = thread_posting_order_++;\n\n pending_queue_.push(std::pair<OrderId, std::unique_ptr<QueuedTask>>(\n order, std::move(task)));\n }\n\n NotifyWake();\n}\n\nvoid TaskQueueStdlib::PostDelayedTask(std::unique_ptr<QueuedTask> task,\n uint32_t milliseconds) {\n auto fire_at = rtc::TimeMillis() + milliseconds;\n\n DelayedEntryTimeout delay;\n delay.next_fire_at_ms_ = fire_at;\n\n {\n MutexLock lock(&pending_lock_);\n delay.order_ = ++thread_posting_order_;\n delayed_queue_[delay] = std::move(task);\n }\n\n NotifyWake();\n}\n\nTaskQueueStdlib::NextTask TaskQueueStdlib::GetNextTask() {\n NextTask result{};\n\n auto tick = rtc::TimeMillis();\n\n MutexLock lock(&pending_lock_);\n\n if (thread_should_quit_) {\n result.final_task_ = true;\n return result;\n }\n\n if (delayed_queue_.size() > 0) {\n auto delayed_entry = delayed_queue_.begin();\n const auto& delay_info = delayed_entry->first;\n auto& delay_run = delayed_entry->second;\n if (tick >= delay_info.next_fire_at_ms_) {\n if (pending_queue_.size() > 0) {\n auto& entry = pending_queue_.front();\n auto& entry_order = entry.first;\n auto& entry_run = entry.second;\n if (entry_order < delay_info.order_) {\n result.run_task_ = std::move(entry_run);\n pending_queue_.pop();\n return result;\n }\n }\n\n result.run_task_ = std::move(delay_run);\n delayed_queue_.erase(delayed_entry);\n return result;\n }\n\n result.sleep_time_ms_ = delay_info.next_fire_at_ms_ - tick;\n }\n\n if (pending_queue_.size() > 0) {\n auto& entry = pending_queue_.front();\n result.run_task_ = std::move(entry.second);\n pending_queue_.pop();\n }\n\n return result;\n}\n\nvoid TaskQueueStdlib::ProcessTasks() {\n started_.Set();\n\n while (true) {\n auto task = GetNextTask();\n\n if (task.final_task_)\n break;\n\n if (task.run_task_) {\n \/\/ process entry immediately then try again\n QueuedTask* release_ptr = task.run_task_.release();\n if (release_ptr->Run())\n delete release_ptr;\n\n \/\/ attempt to sleep again\n continue;\n }\n\n if (0 == task.sleep_time_ms_)\n flag_notify_.Wait(rtc::Event::kForever);\n else\n flag_notify_.Wait(task.sleep_time_ms_);\n }\n}\n\nvoid TaskQueueStdlib::NotifyWake() {\n \/\/ The queue holds pending tasks to complete. Either tasks are to be\n \/\/ executed immediately or tasks are to be run at some future delayed time.\n \/\/ For immediate tasks the task queue's thread is busy running the task and\n \/\/ the thread will not be waiting on the flag_notify_ event. If no immediate\n \/\/ tasks are available but a delayed task is pending then the thread will be\n \/\/ waiting on flag_notify_ with a delayed time-out of the nearest timed task\n \/\/ to run. If no immediate or pending tasks are available, the thread will\n \/\/ wait on flag_notify_ until signaled that a task has been added (or the\n \/\/ thread to be told to shutdown).\n\n \/\/ In all cases, when a new immediate task, delayed task, or request to\n \/\/ shutdown the thread is added the flag_notify_ is signaled after. If the\n \/\/ thread was waiting then the thread will wake up immediately and re-assess\n \/\/ what task needs to be run next (i.e. run a task now, wait for the nearest\n \/\/ timed delayed task, or shutdown the thread). If the thread was not waiting\n \/\/ then the thread will remained signaled to wake up the next time any\n \/\/ attempt to wait on the flag_notify_ event occurs.\n\n \/\/ Any immediate or delayed pending task (or request to shutdown the thread)\n \/\/ must always be added to the queue prior to signaling flag_notify_ to wake\n \/\/ up the possibly sleeping thread. This prevents a race condition where the\n \/\/ thread is notified to wake up but the task queue's thread finds nothing to\n \/\/ do so it waits once again to be signaled where such a signal may never\n \/\/ happen.\n flag_notify_.Set();\n}\n\nclass TaskQueueStdlibFactory final : public TaskQueueFactory {\n public:\n std::unique_ptr<TaskQueueBase, TaskQueueDeleter> CreateTaskQueue(\n absl::string_view name,\n Priority priority) const override {\n return std::unique_ptr<TaskQueueBase, TaskQueueDeleter>(\n new TaskQueueStdlib(name, TaskQueuePriorityToThreadPriority(priority)));\n }\n};\n\n} \/\/ namespace\n\nstd::unique_ptr<TaskQueueFactory> CreateTaskQueueStdlibFactory() {\n return std::make_unique<TaskQueueStdlibFactory>();\n}\n\n} \/\/ namespace webrtc\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"\u4ee5 WebRTC library \u4e3a\u4f8b\uff0c\u8fd9\u4e24\u767e\u884c\u4ee3\u7801\u6f14\u793a\u4e86\u7ebf\u7a0b\u5207\u6362\u7684\u7ecf\u5178\u6a21\u5f0f\u3002 \u4e00\u4e2a\u7ebf\u7a0b\u4f1a\u6709\u4e00\u4e2a\u5bf9\u5e94\u7684\u4efb\u52a1\u961f\u5217\uff0c\u7ebf\u7a0b\u4f1a\u4e0d\u65ad\u68c0\u67e5\u8fd9\u4e2a\u961f\u5217\uff0c\u5982\u679c\u6709\u4efb\u52a1\u5c31\u6267\u884c\uff0c\u65e0\u4efb\u52a1\u5c31\u7b49\u5f85 \u5f80\u8fd9\u4e2a\u4efb\u52a1\u961f\u5217\u4e2d\u63d0\u4ea4\u4e00\u4e2a\u4efb\u52a1\uff0c\u5c31\u7b49\u4e8e\u4ece\u5f53\u524d\u7ebf\u7a0b\u5207\u6362\u4e86\u5230\u4e86\u8fd9\u4e2a\u4efb\u52a1\u7ebf\u7a0b\u3002 \u5f53\u7136\u8fd9\u4e2a\u5b9e\u73b0\u65b9\u9762\u8fd8\u662f\u6709\u4e9b\u7ec6\u8282\uff0c \u4e3a\u4e86\u7ebf\u7a0b\u5b89\u5168\uff0cGetNextTask \u65f6\u9700\u8981\u52a0\u9501 \/* * Copyright 2018 The WebRTC Project Authors. All rights reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights […] →Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-681","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/681"}],"collection":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=681"}],"version-history":[{"count":1,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/681\/revisions"}],"predecessor-version":[{"id":682,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/681\/revisions\/682"}],"wp:attachment":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=681"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=681"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=681"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}