Add systemInfo.cpu.onUpdated event implementation.

chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.cc

Index: chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.cc
diff --git a/chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.cc b/chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.cc
index c7c9cca42ebc1c2ee54fa2f87b3096fa459b3617..660fa1aacba89214f431088eeaa057080c6605c4 100644
--- a/chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.cc
+++ b/chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.cc
@@ -5,10 +5,26 @@
 #include "chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.h"
 
 #include "base/sys_info.h"
+#include "content/public/browser/browser_thread.h"
 
 namespace extensions {
 
 using api::experimental_system_info_cpu::CpuInfo;
+using api::experimental_system_info_cpu::CpuUpdateInfo;
+using content::BrowserThread;
+
+// Default sampling interval is 1000ms.
+const unsigned int kDefaultSamplingIntervalMs = 1000;
+
+CpuInfoProvider::CpuInfoProvider()
+  : is_sampling_started_(false),
+    sampling_timer_(NULL),
+    sampling_interval_(kDefaultSamplingIntervalMs) {
+}
+
+CpuInfoProvider::~CpuInfoProvider() {
+  DCHECK(!sampling_timer_) << "Fogot to call StopSampling?";

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

"StartSampling call without a corresponding StopSampling call" seems like a more
helpful message.

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

Also, this will still leak the sampling timer in non-debug builds.

You may instead want to make sampling_timer_ into a scoped_ptr, so that it'll
still get cleaned up in this case.

+}
 
 bool CpuInfoProvider::QueryInfo(CpuInfo* info) {
   if (info == NULL)
@@ -20,14 +36,52 @@ bool CpuInfoProvider::QueryInfo(CpuInfo* info) {
   return true;
 }
 
-bool CpuInfoProvider::StartSampling(const QueryCpuTimeCallback& callback) {
-  // TODO(hongbo): Implement sampling functionality for event router.
-  return false;
+bool CpuInfoProvider::StartSampling(const SamplingCallback& callback) {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::FILE)) {
+    return BrowserThread::PostTask(
+        BrowserThread::FILE,
+        FROM_HERE,
+        base::Bind(base::IgnoreResult(&CpuInfoProvider::StartSampling),
+                   base::Unretained(this), callback));
+  }
+
+  // We are now on the FILE thread now.
+  if (is_sampling_started_) return true;
+
+  if (!QueryCpuTimePerProcessor(&sampling_value_))
+    return false;
+
+  is_sampling_started_ = true;
+  callback_ = callback;
+
+  DCHECK(!sampling_timer_) << "The sampling timer is leaked. Did you forgot "
+                              "calling StopSampling?";
+
+  // Should be deleted in StopSampling.
+  sampling_timer_ = new base::RepeatingTimer<CpuInfoProvider>();
+
+  sampling_timer_->Start(FROM_HERE,
+      base::TimeDelta::FromMilliseconds(sampling_interval_),
+      this, &CpuInfoProvider::DoStartSampling);

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

DoStartSampling seems like a misnomer, since it isn't called just when starting
to sample, but every sampling interval. Just "DoSample" perhaps?

+
+  return true;
 }
 
 bool CpuInfoProvider::StopSampling() {
-  // TODO(hongbo): Implement sampling functionality for event router.
-  return false;
+  if (!BrowserThread::CurrentlyOn(BrowserThread::FILE)) {
+    return BrowserThread::PostTask(
+        BrowserThread::FILE,
+        FROM_HERE,
+        base::Bind(base::IgnoreResult(&CpuInfoProvider::StopSampling),
+                   base::Unretained(this)));
+  }
+  // We are now on the FILE thread now.
+  if (!is_sampling_started_) return false;
+  delete sampling_timer_;
+  sampling_timer_ = NULL;
+  sampling_value_.clear();
+  is_sampling_started_ = false;
+  return true;
 }
 
 // static
@@ -35,4 +89,35 @@ CpuInfoProvider* CpuInfoProvider::Get() {
   return CpuInfoProvider::GetInstance<CpuInfoProvider>();
 }
 
+void CpuInfoProvider::DoStartSampling() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+
+  std::vector<CpuTime> new_sampling_value;
+  if (!QueryCpuTimePerProcessor(&new_sampling_value))
+    return;
+
+  // Calculate the CPU usage information from the two sampling values.
+  double total_usage = 0;
+  scoped_ptr<CpuUpdateInfo> info(new CpuUpdateInfo());
+
+  for (size_t i = 0; i < new_sampling_value.size(); ++i) {
+    double total_time =
+        (new_sampling_value[i].user - sampling_value_[i].user) +
+        (new_sampling_value[i].kernel - sampling_value_[i].kernel) +
+        (new_sampling_value[i].idle - sampling_value_[i].idle);
+    double idle_time = new_sampling_value[i].idle - sampling_value_[i].idle;
+
+    double usage = 0;
+    if (total_time != 0)
+      usage = (100 - idle_time * 100 / total_time);
+    info->usage_per_processor.push_back(usage);
+    total_usage += usage;
+  }
+
+  info->average_usage = total_usage / new_sampling_value.size();
+
+  if (!callback_.is_null())
+    callback_.Run(info.Pass());
+}
+
 }  // namespace extensions