1 files changed, 326 insertions, 0 deletions
diff --git a/third_party/libwebrtc/rtc_base/task_queue_libevent.cc b/third_party/libwebrtc/rtc_base/task_queue_libevent.cc
new file mode 100644
index 0000000000..10950a295f
--- /dev/null
+++ b/third_party/libwebrtc/rtc_base/task_queue_libevent.cc
@@ -0,0 +1,326 @@
+/*
+ *  Copyright 2016 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 grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "rtc_base/task_queue_libevent.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdint.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <list>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/functional/any_invocable.h"
+#include "absl/strings/string_view.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/time_delta.h"
+#include "event2/event.h"
+#include "event2/event_compat.h"
+#include "event2/event_struct.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_conversions.h"
+#include "rtc_base/platform_thread.h"
+#include "rtc_base/platform_thread_types.h"
+#include "rtc_base/synchronization/mutex.h"
+#include "rtc_base/thread_annotations.h"
+#include "rtc_base/time_utils.h"
+
+namespace webrtc {
+namespace {
+constexpr char kQuit = 1;
+constexpr char kRunTasks = 2;
+
+using Priority = TaskQueueFactory::Priority;
+
+// This ignores the SIGPIPE signal on the calling thread.
+// This signal can be fired when trying to write() to a pipe that's being
+// closed or while closing a pipe that's being written to.
+// We can run into that situation so we ignore this signal and continue as
+// normal.
+// As a side note for this implementation, it would be great if we could safely
+// restore the sigmask, but unfortunately the operation of restoring it, can
+// itself actually cause SIGPIPE to be signaled :-| (e.g. on MacOS)
+// The SIGPIPE signal by default causes the process to be terminated, so we
+// don't want to risk that.
+// An alternative to this approach is to ignore the signal for the whole
+// process:
+//   signal(SIGPIPE, SIG_IGN);
+void IgnoreSigPipeSignalOnCurrentThread() {
+  sigset_t sigpipe_mask;
+  sigemptyset(&sigpipe_mask);
+  sigaddset(&sigpipe_mask, SIGPIPE);
+  pthread_sigmask(SIG_BLOCK, &sigpipe_mask, nullptr);
+}
+
+bool SetNonBlocking(int fd) {
+  const int flags = fcntl(fd, F_GETFL);
+  RTC_CHECK(flags != -1);
+  return (flags & O_NONBLOCK) || fcntl(fd, F_SETFL, flags | O_NONBLOCK) != -1;
+}
+
+// TODO(tommi): This is a hack to support two versions of libevent that we're
+// compatible with.  The method we really want to call is event_assign(),
+// since event_set() has been marked as deprecated (and doesn't accept
+// passing event_base__ as a parameter).  However, the version of libevent
+// that we have in Chromium, doesn't have event_assign(), so we need to call
+// event_set() there.
+void EventAssign(struct event* ev,
+                 struct event_base* base,
+                 int fd,
+                 short events,
+                 void (*callback)(int, short, void*),
+                 void* arg) {
+#if defined(_EVENT2_EVENT_H_)
+  RTC_CHECK_EQ(0, event_assign(ev, base, fd, events, callback, arg));
+#else
+  event_set(ev, fd, events, callback, arg);
+  RTC_CHECK_EQ(0, event_base_set(base, ev));
+#endif
+}
+
+rtc::ThreadPriority TaskQueuePriorityToThreadPriority(Priority priority) {
+  switch (priority) {
+    case Priority::HIGH:
+      return rtc::ThreadPriority::kRealtime;
+    case Priority::LOW:
+      return rtc::ThreadPriority::kLow;
+    case Priority::NORMAL:
+      return rtc::ThreadPriority::kNormal;
+  }
+}
+
+class TaskQueueLibevent final : public TaskQueueBase {
+ public:
+  TaskQueueLibevent(absl::string_view queue_name, rtc::ThreadPriority priority);
+
+  void Delete() override;
+  void PostTask(absl::AnyInvocable<void() &&> task) override;
+  void PostDelayedTask(absl::AnyInvocable<void() &&> task,
+                       TimeDelta delay) override;
+  void PostDelayedHighPrecisionTask(absl::AnyInvocable<void() &&> task,
+                                    TimeDelta delay) override;
+
+ private:
+  struct TimerEvent;
+
+  void PostDelayedTaskOnTaskQueue(absl::AnyInvocable<void() &&> task,
+                                  TimeDelta delay);
+
+  ~TaskQueueLibevent() override = default;
+
+  static void OnWakeup(int socket, short flags, void* context);  // NOLINT
+  static void RunTimer(int fd, short flags, void* context);      // NOLINT
+
+  bool is_active_ = true;
+  int wakeup_pipe_in_ = -1;
+  int wakeup_pipe_out_ = -1;
+  event_base* event_base_;
+  event wakeup_event_;
+  rtc::PlatformThread thread_;
+  Mutex pending_lock_;
+  absl::InlinedVector<absl::AnyInvocable<void() &&>, 4> pending_
+      RTC_GUARDED_BY(pending_lock_);
+  // Holds a list of events pending timers for cleanup when the loop exits.
+  std::list<TimerEvent*> pending_timers_;
+};
+
+struct TaskQueueLibevent::TimerEvent {
+  TimerEvent(TaskQueueLibevent* task_queue, absl::AnyInvocable<void() &&> task)
+      : task_queue(task_queue), task(std::move(task)) {}
+  ~TimerEvent() { event_del(&ev); }
+
+  event ev;
+  TaskQueueLibevent* task_queue;
+  absl::AnyInvocable<void() &&> task;
+};
+
+TaskQueueLibevent::TaskQueueLibevent(absl::string_view queue_name,
+                                     rtc::ThreadPriority priority)
+    : event_base_(event_base_new()) {
+  int fds[2];
+  RTC_CHECK(pipe(fds) == 0);
+  SetNonBlocking(fds[0]);
+  SetNonBlocking(fds[1]);
+  wakeup_pipe_out_ = fds[0];
+  wakeup_pipe_in_ = fds[1];
+
+  EventAssign(&wakeup_event_, event_base_, wakeup_pipe_out_,
+              EV_READ | EV_PERSIST, OnWakeup, this);
+  event_add(&wakeup_event_, 0);
+  thread_ = rtc::PlatformThread::SpawnJoinable(
+      [this] {
+        {
+          CurrentTaskQueueSetter set_current(this);
+          while (is_active_)
+            event_base_loop(event_base_, 0);
+        }
+
+        for (TimerEvent* timer : pending_timers_)
+          delete timer;
+      },
+      queue_name, rtc::ThreadAttributes().SetPriority(priority));
+}
+
+void TaskQueueLibevent::Delete() {
+  RTC_DCHECK(!IsCurrent());
+  struct timespec ts;
+  char message = kQuit;
+  while (write(wakeup_pipe_in_, &message, sizeof(message)) != sizeof(message)) {
+    // The queue is full, so we have no choice but to wait and retry.
+    RTC_CHECK_EQ(EAGAIN, errno);
+    ts.tv_sec = 0;
+    ts.tv_nsec = 1000000;
+    nanosleep(&ts, nullptr);
+  }
+
+  thread_.Finalize();
+
+  event_del(&wakeup_event_);
+
+  IgnoreSigPipeSignalOnCurrentThread();
+
+  close(wakeup_pipe_in_);
+  close(wakeup_pipe_out_);
+  wakeup_pipe_in_ = -1;
+  wakeup_pipe_out_ = -1;
+
+  event_base_free(event_base_);
+  delete this;
+}
+
+void TaskQueueLibevent::PostTask(absl::AnyInvocable<void() &&> task) {
+  {
+    MutexLock lock(&pending_lock_);
+    bool had_pending_tasks = !pending_.empty();
+    pending_.push_back(std::move(task));
+
+    // Only write to the pipe if there were no pending tasks before this one
+    // since the thread could be sleeping. If there were already pending tasks
+    // then we know there's either a pending write in the pipe or the thread has
+    // not yet processed the pending tasks. In either case, the thread will
+    // eventually wake up and process all pending tasks including this one.
+    if (had_pending_tasks) {
+      return;
+    }
+  }
+
+  // Note: This behvior outlined above ensures we never fill up the pipe write
+  // buffer since there will only ever be 1 byte pending.
+  char message = kRunTasks;
+  RTC_CHECK_EQ(write(wakeup_pipe_in_, &message, sizeof(message)),
+               sizeof(message));
+}
+
+void TaskQueueLibevent::PostDelayedTaskOnTaskQueue(
+    absl::AnyInvocable<void() &&> task,
+    TimeDelta delay) {
+  // libevent api is not thread safe by default, thus event_add need to be
+  // called on the `thread_`.
+  RTC_DCHECK(IsCurrent());
+
+  TimerEvent* timer = new TimerEvent(this, std::move(task));
+  EventAssign(&timer->ev, event_base_, -1, 0, &TaskQueueLibevent::RunTimer,
+              timer);
+  pending_timers_.push_back(timer);
+  timeval tv = {.tv_sec = rtc::dchecked_cast<int>(delay.us() / 1'000'000),
+                .tv_usec = rtc::dchecked_cast<int>(delay.us() % 1'000'000)};
+  event_add(&timer->ev, &tv);
+}
+
+void TaskQueueLibevent::PostDelayedTask(absl::AnyInvocable<void() &&> task,
+                                        TimeDelta delay) {
+  if (IsCurrent()) {
+    PostDelayedTaskOnTaskQueue(std::move(task), delay);
+  } else {
+    int64_t posted_us = rtc::TimeMicros();
+    PostTask([posted_us, delay, task = std::move(task), this]() mutable {
+      // Compensate for the time that has passed since the posting.
+      TimeDelta post_time = TimeDelta::Micros(rtc::TimeMicros() - posted_us);
+      PostDelayedTaskOnTaskQueue(
+          std::move(task), std::max(delay - post_time, TimeDelta::Zero()));
+    });
+  }
+}
+
+void TaskQueueLibevent::PostDelayedHighPrecisionTask(
+    absl::AnyInvocable<void() &&> task,
+    TimeDelta delay) {
+  PostDelayedTask(std::move(task), delay);
+}
+
+// static
+void TaskQueueLibevent::OnWakeup(int socket,
+                                 short flags,  // NOLINT
+                                 void* context) {
+  TaskQueueLibevent* me = static_cast<TaskQueueLibevent*>(context);
+  RTC_DCHECK(me->wakeup_pipe_out_ == socket);
+  char buf;
+  RTC_CHECK(sizeof(buf) == read(socket, &buf, sizeof(buf)));
+  switch (buf) {
+    case kQuit:
+      me->is_active_ = false;
+      event_base_loopbreak(me->event_base_);
+      break;
+    case kRunTasks: {
+      absl::InlinedVector<absl::AnyInvocable<void() &&>, 4> tasks;
+      {
+        MutexLock lock(&me->pending_lock_);
+        tasks.swap(me->pending_);
+      }
+      RTC_DCHECK(!tasks.empty());
+      for (auto& task : tasks) {
+        std::move(task)();
+        // Prefer to delete the `task` before running the next one.
+        task = nullptr;
+      }
+      break;
+    }
+    default:
+      RTC_DCHECK_NOTREACHED();
+      break;
+  }
+}
+
+// static
+void TaskQueueLibevent::RunTimer(int fd,
+                                 short flags,  // NOLINT
+                                 void* context) {
+  TimerEvent* timer = static_cast<TimerEvent*>(context);
+  std::move(timer->task)();
+  timer->task_queue->pending_timers_.remove(timer);
+  delete timer;
+}
+
+class TaskQueueLibeventFactory final : public TaskQueueFactory {
+ public:
+  std::unique_ptr<TaskQueueBase, TaskQueueDeleter> CreateTaskQueue(
+      absl::string_view name,
+      Priority priority) const override {
+    return std::unique_ptr<TaskQueueBase, TaskQueueDeleter>(
+        new TaskQueueLibevent(name,
+                              TaskQueuePriorityToThreadPriority(priority)));
+  }
+};
+
+}  // namespace
+
+std::unique_ptr<TaskQueueFactory> CreateTaskQueueLibeventFactory() {
+  return std::make_unique<TaskQueueLibeventFactory>();
+}
+
+}  // namespace webrtc