SystemMonitor refactoring: move power state monitor into a separate class called PowerMonitor

base/power_monitor/power_monitor_mac.mm

 // 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.
 
 // Implementation based on sample code from
 // http://developer.apple.com/library/mac/#qa/qa1340/_index.html.
 
-#include "base/system_monitor/system_monitor.h"
+#include "base/power_monitor/power_monitor.h"
 
 #include <IOKit/pwr_mgt/IOPMLib.h>
 #include <IOKit/IOMessage.h>
 
 namespace base {
 
+// A helper function as a friend function of PowerMonitor.
+void ProcessPowerEventHelper(PowerMonitor::PowerEvent power_event) {
+  PowerMonitor* power_monitor = PowerMonitor::GetInstance();
+  power_monitor->ProcessPowerEvent(power_event);
+}
+
 namespace {
 
 io_connect_t g_system_power_io_port = 0;
 IONotificationPortRef g_notification_port_ref = 0;
 io_object_t g_notifier_object = 0;
 
 void SystemPowerEventCallback(void*,
                               io_service_t service,
                               natural_t message_type,
                               void* message_argument) {
-  SystemMonitor* sys_monitor = SystemMonitor::Get();
-  DCHECK(sys_monitor);
   switch (message_type) {
     case kIOMessageSystemWillSleep:
-      sys_monitor->ProcessPowerMessage(SystemMonitor::SUSPEND_EVENT);
+      ProcessPowerEventHelper(PowerMonitor::SUSPEND_EVENT);
       IOAllowPowerChange(g_system_power_io_port,
           reinterpret_cast<intptr_t>(message_argument));
       break;
 
     case kIOMessageSystemWillPowerOn:
-      sys_monitor->ProcessPowerMessage(SystemMonitor::RESUME_EVENT);
+      ProcessPowerEventHelper(PowerMonitor::RESUME_EVENT);
       break;
   }
 }
 
 }  // namespace
 
 // The reason we can't include this code in the constructor is because
 // PlatformInit() requires an active runloop and the IO port needs to be
 // allocated at sandbox initialization time, before there's a runloop.
 // See crbug.com/83783 .
 
 // static
-void SystemMonitor::AllocateSystemIOPorts() {
+void PowerMonitor::AllocateSystemIOPorts() {
   DCHECK_EQ(g_system_power_io_port, 0u);
 
   // Notification port allocated by IORegisterForSystemPower.
 
   g_system_power_io_port = IORegisterForSystemPower(
       NULL, &g_notification_port_ref, SystemPowerEventCallback,
       &g_notifier_object);
 
   DCHECK_NE(g_system_power_io_port, 0u);
 }
 
-void SystemMonitor::PlatformInit() {
-  // Need to call AllocateSystemIOPorts() before constructing a SystemMonitor
+void PowerMonitor::PlatformInit() {
+  // Need to call AllocateSystemIOPorts() before creating a PowerMonitor
   // object.
   DCHECK_NE(g_system_power_io_port, 0u);
   if (g_system_power_io_port == 0)
     return;

[willchan no longer on Chromium, 2012/10/12 18:17:15]

This makes me minorly nervous, especially now that we lazily create the
PowerMonitor singleton instance. I think before, when we explicitly created it,
anyone trying to use PowerMonitor (SystemMonitor) early would crash on NULL,
since it didn't exist. This could lead to subtle, non-obvious errors. What do
you think about making this a CHECK_NE instead?

[vandebo (ex-Chrome), 2012/10/12 22:12:30]

SGTM

[Hongbo Min, 2012/10/13 06:36:07]

Done.

[Hongbo Min, 2012/10/13 08:22:15]

Willchan, I try to use CHECK_NE instead, but some tests failed on Mac (see the
build bot result of Patch Set 6). So I revert to keep it again.

I suggest to fix this issue in a new CL.

[vandebo (ex-Chrome), 2012/10/15 23:41:25]

It's important to get this stuff right because it will cause crashes otherwise. 
It looks like you need to make SystemMonitor not a class member of
PowerMonitorTest to fix that problem.  AllocateSystemIOPorts has to be called
before PowerMonitor is constructed.

 
   // Add the notification port to the application runloop
   CFRunLoopAddSource(
       CFRunLoopGetCurrent(),
       IONotificationPortGetRunLoopSource(g_notification_port_ref),
       kCFRunLoopCommonModes);
 }
 
-void SystemMonitor::PlatformDestroy() {
+
+void PowerMonitor::PlatformDestroy() {
   DCHECK_NE(g_system_power_io_port, 0u);
   if (g_system_power_io_port == 0)
     return;
 
   // Remove the sleep notification port from the application runloop
   CFRunLoopRemoveSource(
       CFRunLoopGetCurrent(),
       IONotificationPortGetRunLoopSource(g_notification_port_ref),
       kCFRunLoopCommonModes);
 
   // Deregister for system sleep notifications
   IODeregisterForSystemPower(&g_notifier_object);
 
   // IORegisterForSystemPower implicitly opens the Root Power Domain IOService,
   // so we close it here.
   IOServiceClose(g_system_power_io_port);
 
   g_system_power_io_port = 0;
 
   // Destroy the notification port allocated by IORegisterForSystemPower.
   IONotificationPortDestroy(g_notification_port_ref);
 }
 
 }  // namespace base