forwarder2: Make the Forwarder instances operate on a single thread.

tools/android/forwarder2/forwarders_manager.cc

 // Copyright 2013 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 "tools/android/forwarder2/forwarders_manager.h"
 
+#include <sys/select.h>
+#include <unistd.h>
+
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop_proxy.h"
+#include "base/posix/eintr_wrapper.h"
 #include "tools/android/forwarder2/forwarder.h"
 #include "tools/android/forwarder2/socket.h"
 
 namespace forwarder2 {
 
-ForwardersManager::ForwardersManager() : delegate_(new Delegate()) {}
+ForwardersManager::ForwardersManager() : thread_("ForwardersManagerThread") {
+  thread_.Start();
+}
+
 
 ForwardersManager::~ForwardersManager() {
-  delegate_->Clear();
+  deletion_notifier_.Notify();
 }
 
 void ForwardersManager::CreateAndStartNewForwarder(scoped_ptr<Socket> socket1,
                                                    scoped_ptr<Socket> socket2) {
-  delegate_->CreateAndStartNewForwarder(socket1.Pass(), socket2.Pass());
+  // Note that the internal Forwarder vector is populated on the internal thread
+  // which is the only thread from which it's accessed.
+  thread_.message_loop_proxy()->PostTask(
+      FROM_HERE,
+      base::Bind(&ForwardersManager::CreateNewForwarderOnInternalThread,
+                 base::Unretained(this), base::Passed(&socket1),
+                 base::Passed(&socket2)));
+
+  // Guarantees that the CreateNewForwarderOnInternalThread callback posted to
+  // the internal thread gets executed immediately.
+  wakeup_notifier_.Notify();
+
+  WaitForEventsOnInternalThreadSoon();
 }
 
-ForwardersManager::Delegate::Delegate() {}
-
-ForwardersManager::Delegate::~Delegate() {
-  // The forwarder instances should already have been deleted on their
-  // construction thread. Deleting them here would be unsafe since we don't know
-  // which thread this destructor is called on.
-  DCHECK(forwarders_.empty());
+void ForwardersManager::CreateNewForwarderOnInternalThread(
+    scoped_ptr<Socket> socket1,
+    scoped_ptr<Socket> socket2) {
+  DCHECK(thread_.message_loop_proxy()->RunsTasksOnCurrentThread());
+  forwarders_.push_back(new Forwarder(socket1.Pass(), socket2.Pass()));
+  wakeup_notifier_.Reset();
 }
 
-void ForwardersManager::Delegate::Clear() {
-  if (!forwarders_constructor_runner_) {
-    DCHECK(forwarders_.empty());
+void ForwardersManager::WaitForEventsOnInternalThreadSoon() {
+  thread_.message_loop_proxy()->PostTask(
+      FROM_HERE,
+      base::Bind(&ForwardersManager::WaitForEventsOnInternalThread,
+                 base::Unretained(this)));
+}
+
+void ForwardersManager::WaitForEventsOnInternalThread() {
+  DCHECK(thread_.message_loop_proxy()->RunsTasksOnCurrentThread());
+  if (forwarders_.empty())
+    return;
+
+  fd_set read_fds;
+  fd_set write_fds;
+
+  FD_ZERO(&read_fds);
+  FD_ZERO(&write_fds);
+
+  // Populate the file descriptor sets.
+  int max_fd = -1;
+  for (ScopedVector<Forwarder>::iterator it = forwarders_.begin();
+       it != forwarders_.end(); ++it) {
+    Forwarder* const forwarder = *it;
+    forwarder->RegisterFDs(&read_fds, &write_fds, &max_fd);
+  }
+
+  const int notifier_fds[] = {
+    wakeup_notifier_.receiver_fd(),
+    deletion_notifier_.receiver_fd(),
+  };
+
+  for (int i = 0; i < arraysize(notifier_fds); ++i) {
+    const int notifier_fd = notifier_fds[i];
+    DCHECK_GT(notifier_fd, -1);
+    FD_SET(notifier_fd, &read_fds);
+    max_fd = std::max(max_fd, notifier_fd);
+  }
+
+  const int ret = HANDLE_EINTR(
+      select(max_fd + 1, &read_fds, &write_fds, NULL, NULL));
+  if (ret < 0) {
+    PLOG(ERROR) << "select";
     return;
   }
-  if (forwarders_constructor_runner_->RunsTasksOnCurrentThread()) {
-    ClearOnForwarderConstructorThread();
+
+  if (FD_ISSET(wakeup_notifier_.receiver_fd(), &read_fds)) {
+    // Note that the events on FDs other than the wakeup notifier one, if any,
+    // will be processed upon the next select().
     return;
   }
-  forwarders_constructor_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(
-          &ForwardersManager::Delegate::ClearOnForwarderConstructorThread,
-          this));
-}
 
-void ForwardersManager::Delegate::CreateAndStartNewForwarder(
-    scoped_ptr<Socket> socket1,
-    scoped_ptr<Socket> socket2) {
-  const scoped_refptr<base::SingleThreadTaskRunner> current_task_runner(
-      base::MessageLoopProxy::current());
-  DCHECK(current_task_runner);
-  if (forwarders_constructor_runner_) {
-    DCHECK_EQ(current_task_runner, forwarders_constructor_runner_);
-  } else {
-    forwarders_constructor_runner_ = current_task_runner;
+  // Notify the Forwarder instances and remove the ones that are closed.
+  const bool must_shutdown = FD_ISSET(
+      deletion_notifier_.receiver_fd(), &read_fds);
+
+  for (size_t i = 0; i < forwarders_.size(); ) {
+    Forwarder* const forwarder = forwarders_[i];
+    forwarder->ProcessEvents(read_fds, write_fds);
+
+    if (must_shutdown)
+      forwarder->Shutdown();
+
+    if (!forwarder->IsClosed()) {
+      ++i;
+      continue;
+    }
+
+    std::swap(forwarders_[i], forwarders_.back());
+    forwarders_.pop_back();
   }
-  forwarders_.push_back(
-      new Forwarder(socket1.Pass(), socket2.Pass(),
-                    &deletion_notifier_,
-                    base::Bind(&ForwardersManager::Delegate::OnForwarderError,
-                               this)));
-  forwarders_.back()->Start();
-}
 
-void ForwardersManager::Delegate::OnForwarderError(
-    scoped_ptr<Forwarder> forwarder) {
-  DCHECK(forwarders_constructor_runner_->RunsTasksOnCurrentThread());
-  const ScopedVector<Forwarder>::iterator it = std::find(
-      forwarders_.begin(), forwarders_.end(), forwarder.get());
-  DCHECK(it != forwarders_.end());
-  std::swap(*it, forwarders_.back());
-  forwarders_.pop_back();
-  ignore_result(forwarder.release());  // Deleted by the pop_back() above.
-}
-
-void ForwardersManager::Delegate::ClearOnForwarderConstructorThread() {
-  DCHECK(forwarders_constructor_runner_->RunsTasksOnCurrentThread());
-  deletion_notifier_.Notify();
-  forwarders_.clear();
+  WaitForEventsOnInternalThreadSoon();
 }
 
 }  // namespace forwarder2