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"
+
+namespace gamepad {
+
+using namespace content;
+
+Provider::Provider(DataFetcher* fetcher)
+    : creator_loop_(MessageLoop::current()),
+      provided_fetcher_(fetcher),
+      devices_changed_(true),
+      ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
+  const size_t DataSize = sizeof(GamepadHardwareBuffer);

[jam, 2011/11/16 00:24:58]

nit: data_size per style guide. also, from what I've seen, we avoid const in
local variables.

[scottmg, 2011/11/16 18:04:35]

Done.

+  base::SystemMonitor* monitor = base::SystemMonitor::Get();
+  if (monitor)
+    monitor->AddDevicesChangedObserver(this);
+  gamepad_shared_memory_.CreateAndMapAnonymous(DataSize);
+  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() == 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,

[jam, 2011/11/16 00:24:58]

nit: this style of spacing isn't in the style guide afaik, since both parameters
should be tabbed the same, so i think FROM_HERE should be in the next line
tabbed 4 spaces

[scottmg, 2011/11/16 18:04:35]

Done.

+      base::Bind(&Provider::DoInitializePollingThread, this));
+}
+
+void Provider::Stop() {
+  DCHECK(MessageLoop::current() == 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();
+

[jam, 2011/11/16 00:24:58]

nit: i'm not sure why each line in this function is separated by a blank line?

[scottmg, 2011/11/16 18:04:35]

Done.

+  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,

[jam, 2011/11/16 00:24:58]

nit: ditto for tabbing

[scottmg, 2011/11/16 18:04:35]

Done.

+      base::Bind(&Provider::DoPoll, weak_factory_.GetWeakPtr()),
+      kDesiredSamplingIntervalMs);
+}
+
+GamepadHardwareBuffer* Provider::SharedMemoryAsHardwareBuffer() {
+  void* mem = gamepad_shared_memory_.memory();
+  DCHECK(mem);
+  return static_cast<GamepadHardwareBuffer*>(mem);
+}
+
+Provider* Provider::instance_ = NULL;

[jam, 2011/11/16 00:24:58]

nit: statics get listed at the top of the file before functions

[scottmg, 2011/11/16 18:04:35]

Done.

+
+}  // namespace gamepad