message_loop_android.cc

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#include "flutter/fml/platform/android/message_loop_android.h"
 
#include <fcntl.h>
#include <unistd.h>
 
#include "flutter/fml/platform/linux/timerfd.h"
 
namespace fml {
 
static constexpr int kClockType = CLOCK_MONOTONIC;
 
static ALooper* AcquireLooperForThread() {
  ALooper* looper = ALooper_forThread();
 
  if (looper == nullptr) {
    // No looper has been configured for the current thread. Create one and
    // return the same.
    looper = ALooper_prepare(0);
  }
 
  // The thread already has a looper. Acquire a reference to the same and return
  // it.
  ALooper_acquire(looper);
  return looper;
}
 
MessageLoopAndroid::MessageLoopAndroid()
    : looper_(AcquireLooperForThread()),
      timer_fd_(::timerfd_create(kClockType, TFD_NONBLOCK | TFD_CLOEXEC)) {
  FML_CHECK(looper_.is_valid());
  FML_CHECK(timer_fd_.is_valid());
 
  static const int kWakeEvents = ALOOPER_EVENT_INPUT;
 
  ALooper_callbackFunc read_event_fd = [](int, int events, void* data) -> int {
    if (events & kWakeEvents) {
      reinterpret_cast<MessageLoopAndroid*>(data)->OnEventFired();
    }
    return 1;  // continue receiving callbacks
  };
 
  int add_result = ::ALooper_addFd(looper_.get(),          // looper
                                   timer_fd_.get(),        // fd
                                   ALOOPER_POLL_CALLBACK,  // ident
                                   kWakeEvents,            // events
                                   read_event_fd,          // callback
                                   this                    // baton
  );
  FML_CHECK(add_result == 1);
}
 
MessageLoopAndroid::~MessageLoopAndroid() {
  int remove_result = ::ALooper_removeFd(looper_.get(), timer_fd_.get());
  FML_CHECK(remove_result == 1);
}
 
void MessageLoopAndroid::Run() {
  FML_DCHECK(looper_.get() == ALooper_forThread());
 
  running_ = true;
 
  while (running_) {
    int result = ::ALooper_pollOnce(-1,       // infinite timeout
                                    nullptr,  // out fd,
                                    nullptr,  // out events,
                                    nullptr   // out data
    );
    if (result == ALOOPER_POLL_TIMEOUT || result == ALOOPER_POLL_ERROR) {
      // This handles the case where the loop is terminated using ALooper APIs.
      running_ = false;
    }
  }
}
 
void MessageLoopAndroid::Terminate() {
  running_ = false;
  ALooper_wake(looper_.get());
}
 
void MessageLoopAndroid::WakeUp(fml::TimePoint time_point) {
  [[maybe_unused]] bool result = TimerRearm(timer_fd_.get(), time_point);
  FML_DCHECK(result);
}
 
void MessageLoopAndroid::OnEventFired() {
  if (TimerDrain(timer_fd_.get())) {
    RunExpiredTasksNow();
  }
}
 
}  // namespace fml