The Linux FML backend. (flutter/engine#3488)

engine/src/flutter/fml/platform/linux/message_loop_linux.cc

@@ -0,0 +1,90 @@
+// Copyright 2017 The Chromium 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/linux/message_loop_linux.h"
+
+#include <sys/epoll.h>
+#include <unistd.h>
+
+#include "flutter/fml/platform/linux/timerfd.h"
+#include "lib/ftl/files/eintr_wrapper.h"
+
+namespace fml {
+
+static constexpr int kClockType = CLOCK_MONOTONIC;
+
+MessageLoopLinux::MessageLoopLinux()
+    : epoll_fd_(HANDLE_EINTR(::epoll_create(1 /* unused */))),
+      timer_fd_(::timerfd_create(kClockType, TFD_NONBLOCK | TFD_CLOEXEC)),
+      running_(false) {
+  FTL_CHECK(epoll_fd_.is_valid());
+  FTL_CHECK(timer_fd_.is_valid());
+  bool added_source = AddOrRemoveTimerSource(true);
+  FTL_CHECK(added_source);
+}
+
+MessageLoopLinux::~MessageLoopLinux() {
+  bool removed_source = AddOrRemoveTimerSource(false);
+  FTL_CHECK(removed_source);
+}
+
+bool MessageLoopLinux::AddOrRemoveTimerSource(bool add) {
+  struct epoll_event event = {};
+
+  event.events = EPOLLIN;
+  // The data is just for informational purposes so we know when we were worken
+  // by the FD.
+  event.data.fd = timer_fd_.get();
+
+  int ctl_result =
+      ::epoll_ctl(epoll_fd_.get(), add ? EPOLL_CTL_ADD : EPOLL_CTL_DEL,
+                  timer_fd_.get(), &event);
+  return ctl_result == 0;
+}
+
+void MessageLoopLinux::Run() {
+  running_ = true;
+
+  while (running_) {
+    struct epoll_event event = {};
+
+    int epoll_result = HANDLE_EINTR(
+        ::epoll_wait(epoll_fd_.get(), &event, 1, -1 /* timeout */));
+
+    // Errors are fatal.
+    if (event.events & (EPOLLERR | EPOLLHUP)) {
+      running_ = false;
+      continue;
+    }
+
+    // Timeouts are fatal since we specified an infinite timeout already.
+    // Likewise, > 1 is not possible since we waited for one result.
+    if (epoll_result != 1) {
+      running_ = false;
+      continue;
+    }
+
+    if (event.data.fd == timer_fd_.get()) {
+      OnEventFired();
+    }
+  }
+}
+
+void MessageLoopLinux::Terminate() {
+  running_ = false;
+  WakeUp(ftl::TimePoint::Now());
+}
+
+void MessageLoopLinux::WakeUp(ftl::TimePoint time_point) {
+  bool result = TimerRearm(timer_fd_.get(), time_point);
+  FTL_DCHECK(result);
+}
+
+void MessageLoopLinux::OnEventFired() {
+  if (TimerDrain(timer_fd_.get())) {
+    RunExpiredTasksNow();
+  }
+}
+
+}  // namespace fml

engine/src/flutter/fml/platform/linux/message_loop_linux.h

@@ -0,0 +1,43 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_FML_PLATFORM_LINUX_MESSAGE_LOOP_LINUX_H_
+#define FLUTTER_FML_PLATFORM_LINUX_MESSAGE_LOOP_LINUX_H_
+
+#include <atomic>
+
+#include "flutter/fml/message_loop_impl.h"
+#include "lib/ftl/files/unique_fd.h"
+#include "lib/ftl/macros.h"
+
+namespace fml {
+
+class MessageLoopLinux : public MessageLoopImpl {
+ private:
+  ftl::UniqueFD epoll_fd_;
+  ftl::UniqueFD timer_fd_;
+  bool running_;
+
+  MessageLoopLinux();
+
+  ~MessageLoopLinux() override;
+
+  void Run() override;
+
+  void Terminate() override;
+
+  void WakeUp(ftl::TimePoint time_point) override;
+
+  void OnEventFired();
+
+  bool AddOrRemoveTimerSource(bool add);
+
+  FRIEND_MAKE_REF_COUNTED(MessageLoopLinux);
+  FRIEND_REF_COUNTED_THREAD_SAFE(MessageLoopLinux);
+  FTL_DISALLOW_COPY_AND_ASSIGN(MessageLoopLinux);
+};
+
+}  // namespace fml
+
+#endif  // FLUTTER_FML_PLATFORM_LINUX_MESSAGE_LOOP_LINUX_H_

engine/src/flutter/fml/platform/linux/timerfd.cc

@@ -0,0 +1,58 @@
+// Copyright 2017 The Chromium 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/linux/timerfd.h"
+
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "lib/ftl/files/eintr_wrapper.h"
+
+#if FML_TIMERFD_AVAILABLE == 0
+
+#include <asm/unistd.h>
+#include <sys/syscall.h>
+
+int timerfd_create(int clockid, int flags) {
+  return syscall(__NR_timerfd_create, clockid, flags);
+}
+
+int timerfd_settime(int ufc,
+                    int flags,
+                    const struct itimerspec* utmr,
+                    struct itimerspec* otmr) {
+  return syscall(__NR_timerfd_settime, ufc, flags, utmr, otmr);
+}
+
+#endif  // FML_TIMERFD_AVAILABLE == 0
+
+namespace fml {
+
+#ifndef NSEC_PER_SEC
+#define NSEC_PER_SEC 1000000000
+#endif
+
+bool TimerRearm(int fd, ftl::TimePoint time_point) {
+  const uint64_t nano_secs = time_point.ToEpochDelta().ToNanoseconds();
+
+  struct itimerspec spec = {};
+  spec.it_value.tv_sec = (time_t)(nano_secs / NSEC_PER_SEC);
+  spec.it_value.tv_nsec = nano_secs % NSEC_PER_SEC;
+  spec.it_interval = spec.it_value;  // single expiry.
+
+  int result = ::timerfd_settime(fd, TFD_TIMER_ABSTIME, &spec, nullptr);
+  return result == 0;
+}
+
+bool TimerDrain(int fd) {
+  // 8 bytes must be read from a signalled timer file descriptor when signalled.
+  uint64_t fire_count = 0;
+  ssize_t size = HANDLE_EINTR(::read(fd, &fire_count, sizeof(uint64_t)));
+  if (size != sizeof(uint64_t)) {
+    return false;
+  }
+  return fire_count > 0;
+}
+
+}  // namespace fml

engine/src/flutter/fml/platform/linux/timerfd.h

@@ -0,0 +1,53 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_FML_PLATFORM_LINUX_TIMER_FD_H_
+#define FLUTTER_FML_PLATFORM_LINUX_TIMER_FD_H_
+
+#include "lib/ftl/time/time_point.h"
+
+// clang-format off
+#if __has_include(<sys/timerfd.h>)
+// clang-format on
+
+#include <sys/timerfd.h>
+
+#define FML_TIMERFD_AVAILABLE 1
+
+#else  // __has_include(<sys/timerfd.h>)
+
+#define FML_TIMERFD_AVAILABLE 0
+
+#include <sys/types.h>
+// Must come after sys/types
+#include <linux/time.h>
+
+#define TFD_TIMER_ABSTIME (1 << 0)
+#define TFD_TIMER_CANCEL_ON_SET (1 << 1)
+
+#define TFD_CLOEXEC O_CLOEXEC
+#define TFD_NONBLOCK O_NONBLOCK
+
+int timerfd_create(int clockid, int flags);
+
+int timerfd_settime(int ufc,
+                    int flags,
+                    const struct itimerspec* utmr,
+                    struct itimerspec* otmr);
+
+#endif  // __has_include(<sys/timerfd.h>)
+
+namespace fml {
+
+/// Rearms the timer to expire at the given time point.
+bool TimerRearm(int fd, ftl::TimePoint time_point);
+
+/// Drains the timer FD and retuns true if it has expired. This may be false in
+/// case the timer read is non-blocking and this routine was called before the
+/// timer expiry.
+bool TimerDrain(int fd);
+
+}  // namespace fml
+
+#endif  // FLUTTER_FML_PLATFORM_LINUX_TIMER_FD_H_