add device notification to Mac

content/browser/device_monitor_mac.cc

Index: content/browser/device_monitor_mac.cc
diff --git a/content/browser/device_monitor_mac.cc b/content/browser/device_monitor_mac.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0ca48cf68d8f19398be1338d8b0b57edca98ecd6
--- /dev/null
+++ b/content/browser/device_monitor_mac.cc
@@ -0,0 +1,166 @@
+// Copyright (c) 2012 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 "content/browser/device_monitor_mac.h"
+
+#include <IOKit/audio/IOAudioDefines.h>
+#include <IOKit/usb/IOUSBLib.h>
+
+#include "base/logging.h"
+#include "base/mac/scoped_cftyperef.h"
+#include "base/mac/scoped_ioobject.h"
+
+namespace content {
+
+namespace {

[Mark Mentovai, 2012/08/14 15:37:05]

We also usually put a blank line after opening a namespace, before the kServices
array.

[no longer working on chromium, 2012/08/14 15:59:36]

Done.

+const io_name_t kServices[] = {
+  kIOFirstPublishNotification,
+  kIOTerminatedNotification,
+};
+
+CFMutableDictionaryRef CreateMatchingDictionaryForUSBDevices(
+    SInt32 interface_class_code, SInt32 interface_subclass_code) {
+  CFMutableDictionaryRef matching_dictionary = IOServiceMatching(

[Mark Mentovai, 2012/08/14 15:37:05]

This is more legible when you break the line after the =, as in

  CFMutableDictionaryRef matching_dictionary =
      IOServiceMatching(kIOUSBInterfaceClassName);

[no longer working on chromium, 2012/08/14 15:59:36]

Done.

+      kIOUSBInterfaceClassName);
+  base::mac::ScopedCFTypeRef<CFNumberRef> number_ref(CFNumberCreate(
+      kCFAllocatorDefault, kCFNumberSInt32Type, &interface_class_code));
+  DCHECK(number_ref);
+  CFDictionaryAddValue(matching_dictionary, CFSTR(kUSBInterfaceClass),
+                       number_ref);
+
+  number_ref.reset(CFNumberCreate(kCFAllocatorDefault,
+                                  kCFNumberSInt32Type,
+                                  &interface_subclass_code));
+  DCHECK(number_ref);
+  CFDictionaryAddValue(matching_dictionary, CFSTR(kUSBInterfaceSubClass),
+                       number_ref);
+
+  return matching_dictionary;
+}
+
+void RegisterCallbackToIOService(IONotificationPortRef port,
+                                 const io_name_t type,
+                                 CFMutableDictionaryRef dictionary,
+                                 IOServiceMatchingCallback callback,
+                                 void* context,
+                                 io_iterator_t* service) {
+  kern_return_t err = IOServiceAddMatchingNotification(port,
+                                                       type,
+                                                       dictionary,
+                                                       callback,
+                                                       context,
+                                                       service);
+  if (err) {
+    NOTREACHED() << "Failed to register the IO matched notification for type "
+                 << type;
+    return;
+  }
+  DCHECK(*service);
+
+  // Iterate over set of matching devices to access already-present devices
+  // and to arm the notification.
+  for (base::mac::ScopedIOObject<io_service_t> object(IOIteratorNext(*service));
+       object;
+       object.reset(IOIteratorNext(*service))) {};
+}
+
+}  // namespace
+
+DeviceMonitorMac::DeviceMonitorMac() {
+

[Mark Mentovai, 2012/08/14 15:37:05]

But we don’t usually begin functions (or constructors) with blank lines.

[no longer working on chromium, 2012/08/14 15:59:36]

Done.

+  // Add the notification port to the run loop.
+  notification_port_ = IONotificationPortCreate(kIOMasterPortDefault);
+  DCHECK(notification_port_);
+
+  RegisterAudioServices();
+  RegisterVideoServices();
+
+  CFRunLoopAddSource(CFRunLoopGetCurrent(),
+                     IONotificationPortGetRunLoopSource(notification_port_),
+                     kCFRunLoopCommonModes);
+}
+
+DeviceMonitorMac::~DeviceMonitorMac() {
+  // Stop the notifications and free the objects.
+  for (size_t i = 0; i < notification_iterators_.size(); ++i) {
+    IOObjectRelease(*notification_iterators_[i]);
+  }
+  notification_iterators_.clear();
+
+  // Remove the sleep notification port from the application runloop.

[Mark Mentovai, 2012/08/14 15:37:05]

This seems like a copy-paste job. This code has nothing to do with sleep.

[no longer working on chromium, 2012/08/14 15:59:36]

Done.

+  CFRunLoopRemoveSource(CFRunLoopGetCurrent(),
+                        IONotificationPortGetRunLoopSource(notification_port_),
+                        kCFRunLoopCommonModes);
+
+  // Destroy the notification port allocated by IONotificationPortCreate.
+  IONotificationPortDestroy(notification_port_);
+}
+
+void DeviceMonitorMac::RegisterAudioServices() {
+  CFMutableDictionaryRef dictionary = IOServiceMatching(

[Mark Mentovai, 2012/08/14 15:37:05]

Rewrap for readability as I suggested on line 24.

[no longer working on chromium, 2012/08/14 15:59:36]

Done.

+      kIOAudioDeviceClassName);
+  RegisterServices(dictionary, &AudioDeviceCallback);
+}
+
+void DeviceMonitorMac::RegisterVideoServices() {
+  CFMutableDictionaryRef dictionary = CreateMatchingDictionaryForUSBDevices(
+      kUSBVideoInterfaceClass, kUSBVideoControlSubClass);
+  RegisterServices(dictionary, &VideoDeviceCallback);
+}
+
+void DeviceMonitorMac::RegisterServices(CFMutableDictionaryRef dictionary,
+                                        IOServiceMatchingCallback callback) {
+  // Add callback to the service.
+  for (size_t i = 0; i < arraysize(kServices); ++i) {
+    // Retain |arraysize(kServices) -1| additional dictionary references because

[Mark Mentovai, 2012/08/14 15:37:05]

I don’t understand why you only do this for arraysize(kServices) - 1.

[no longer working on chromium, 2012/08/14 15:59:36]

When creating the CFMutableDictionaryRef, the ref counter has increased to 1.
So calling |arraysize(kServices) - 1| times CFRetain will increase the ref
counter to |arraysize(kServices)|, which is exactly the number of times we call
IOServiceAddMatchingNotification.

[Mark Mentovai, 2012/08/14 16:02:53]

xians1 wrote:
OK, so the missing piece (in my mind) was that dictionary comes in with a retain
count of 1, which will be consumed by a single RegisterCallbackToIOService call,
and you want to retain the dictionary once for each of the other calls.

Can you reword the comment slightly to make this clearer? Your e-mail
explanation was good, but the comment here didn’t make the “comes in with retain
count 1, and that gets used” aspect clear.

+    // each call to IOServiceAddMatchingNotification consumes one reference.
+    if (i < (arraysize(kServices) - 1))
+      CFRetain(dictionary);
+
+    // Register callback to each service.
+    io_iterator_t service;
+    RegisterCallbackToIOService(notification_port_,
+                                kServices[i],
+                                dictionary,
+                                callback,
+                                this,
+                                &service);
+
+    // Store the pointer of the object to release the memory when shutting
+    // down the services.
+    notification_iterators_.push_back(&service);
+  }
+}
+
+void DeviceMonitorMac::AudioDeviceCallback(void *context,
+                                           io_iterator_t iterator) {
+ for (base::mac::ScopedIOObject<io_service_t> object(IOIteratorNext(iterator));
+      object;
+      object.reset(IOIteratorNext(iterator))) {
+    if (context) {
+      reinterpret_cast<DeviceMonitorMac*>(context)->NotifyDeviceChanged(
+          base::SystemMonitor::DEVTYPE_AUDIO_CAPTURE);
+    }
+  }
+}
+
+void DeviceMonitorMac::VideoDeviceCallback(void *context,
+                                           io_iterator_t iterator) {
+  for (base::mac::ScopedIOObject<io_service_t> object(IOIteratorNext(iterator));
+       object;
+       object.reset(IOIteratorNext(iterator))) {
+    if (context) {
+      reinterpret_cast<DeviceMonitorMac*>(context)->NotifyDeviceChanged(
+          base::SystemMonitor::DEVTYPE_VIDEO_CAPTURE);
+    }
+  }
+}
+
+void DeviceMonitorMac::NotifyDeviceChanged(
+    base::SystemMonitor::DeviceType type) {
+  // TODO(xians): Remove the global variable for SystemMonitor.
+  base::SystemMonitor::Get()->ProcessDevicesChanged(type);
+}
+
+}  // namespace content