Add gamepad hardware data fetcher, and higher level thread container

content/browser/gamepad/gamepad_provider.cc

+// Copyright (c) 2011 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 <cmath>
+#include <set>
+#include <vector>
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/message_loop.h"
+#include "base/task.h"
+#include "base/threading/thread.h"
+#include "base/threading/thread_restrictions.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/browser/gamepad/gamepad_provider.h"
+#include "content/browser/gamepad/data_fetcher.h"
+#include "content/common/gamepad_messages.h"
+
+#if defined(OS_WIN)
+#include "content/browser/gamepad/data_fetcher_win.h"
+#endif
+
+namespace gamepad {
+
+Provider* Provider::instance_ = NULL;
+
+using namespace content;
+
+// Define the default data fetcher that Provider will use if none is supplied.
+// (PlatformDataFetcher).
+#if defined(OS_WIN)
+
+typedef DataFetcherWindows PlatformDataFetcher;
+
+#else
+
+class EmptyDataFetcher : public DataFetcher {
+ public:
+  void GetGamepadData(WebKit::WebGamepads* pads, bool) {
+    pads->length = 0;
+  }
+};
+typedef EmptyDataFetcher PlatformDataFetcher;
+
+#endif
+
+Provider::Provider(DataFetcher* fetcher)
+    : creator_loop_(MessageLoop::current()->message_loop_proxy()),
+      provided_fetcher_(fetcher),
+      devices_changed_(true),
+      ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
+  size_t data_size = sizeof(GamepadHardwareBuffer);
+  base::SystemMonitor* monitor = base::SystemMonitor::Get();
+  if (monitor)
+    monitor->AddDevicesChangedObserver(this);
+  gamepad_shared_memory_.CreateAndMapAnonymous(data_size);
+  GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
+  memset(hwbuf, 0, sizeof(GamepadHardwareBuffer));
+}
+
+Provider::~Provider() {
+  base::SystemMonitor* monitor = base::SystemMonitor::Get();
+  if (monitor)
+    monitor->RemoveDevicesChangedObserver(this);
+  Stop();
+}
+
+base::SharedMemoryHandle Provider::GetRendererSharedMemoryHandle(
+    base::ProcessHandle process) {
+  base::SharedMemoryHandle renderer_handle;
+  gamepad_shared_memory_.ShareToProcess(process, &renderer_handle);
+  return renderer_handle;
+}
+
+void Provider::OnDevicesChanged() {
+  devices_changed_ = true;
+}
+
+void Provider::Start() {
+  DCHECK(MessageLoop::current()->message_loop_proxy() == creator_loop_);
+
+  if (polling_thread_.get())
+    return;
+
+  polling_thread_.reset(new base::Thread("Gamepad polling thread"));
+  if (!polling_thread_->Start()) {
+    LOG(ERROR) << "Failed to start gamepad polling thread";
+    polling_thread_.reset();
+    return;
+  }
+
+  MessageLoop* polling_loop = polling_thread_->message_loop();
+  polling_loop->PostTask(
+      FROM_HERE,
+      base::Bind(&Provider::DoInitializePollingThread, this));
+}
+
+void Provider::Stop() {
+  DCHECK(MessageLoop::current()->message_loop_proxy() == creator_loop_);
+
+  polling_thread_.reset();
+  data_fetcher_.reset();
+}
+
+void Provider::DoInitializePollingThread() {
+  DCHECK(MessageLoop::current() == polling_thread_->message_loop());
+
+  if (!provided_fetcher_.get())
+    provided_fetcher_.reset(new PlatformDataFetcher);
+
+  // Pass ownership of fetcher to provider_.
+  data_fetcher_.swap(provided_fetcher_);
+
+  // Start polling.
+  ScheduleDoPoll();
+}
+
+void Provider::DoPoll() {
+  DCHECK(MessageLoop::current() == polling_thread_->message_loop());
+  GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
+  base::subtle::Barrier_AtomicIncrement(&hwbuf->start_marker, 1);
+  data_fetcher_->GetGamepadData(&hwbuf->buffer, devices_changed_);
+  base::subtle::Barrier_AtomicIncrement(&hwbuf->end_marker, 1);
+  devices_changed_ = false;
+  // Schedule our next interval of polling.
+  ScheduleDoPoll();
+}
+
+void Provider::ScheduleDoPoll() {
+  DCHECK(MessageLoop::current() == polling_thread_->message_loop());
+
+  MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&Provider::DoPoll, weak_factory_.GetWeakPtr()),
+      kDesiredSamplingIntervalMs);
+}
+
+GamepadHardwareBuffer* Provider::SharedMemoryAsHardwareBuffer() {
+  void* mem = gamepad_shared_memory_.memory();
+  DCHECK(mem);
+  return static_cast<GamepadHardwareBuffer*>(mem);
+}
+
+}  // namespace gamepad