[chromeos] Limit the data samples stored by PowerDataCollector.

chromeos/power/power_data_collector.cc

 // Copyright 2013 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 "chromeos/power/power_data_collector.h"
 
 #include "base/logging.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/power_manager/power_supply_properties.pb.h"
 
 namespace chromeos {
 
 namespace {
 
 // The global PowerDataCollector instance.
 PowerDataCollector* g_power_data_collector = NULL;
 
 }  // namespace
 
+const int PowerDataCollector::kSampleTimeLimitSec = 24 * 60 * 60;
+
 // static
 void PowerDataCollector::Initialize() {
   // Check that power data collector is initialized only after the
   // DBusThreadManager is initialized.
   CHECK(DBusThreadManager::Get());
   CHECK(g_power_data_collector == NULL);
   g_power_data_collector = new PowerDataCollector();
 }
 
 // static
@@ skipping 10 matching lines @@
   return g_power_data_collector;
 }
 
 void PowerDataCollector::PowerChanged(
     const power_manager::PowerSupplyProperties& prop) {
   PowerSupplySnapshot snapshot;
   snapshot.time = base::TimeTicks::Now();
   snapshot.external_power = (prop.external_power() !=
       power_manager::PowerSupplyProperties::DISCONNECTED);
   snapshot.battery_percent = prop.battery_percent();
-
-  power_supply_data_.push_back(snapshot);
+  AddSnapshot(snapshot);
 }
 
 PowerDataCollector::PowerDataCollector() {
   DBusThreadManager::Get()->GetPowerManagerClient()->AddObserver(this);
 }
 
 PowerDataCollector::~PowerDataCollector() {
   DBusThreadManager* dbus_manager = DBusThreadManager::Get();
   CHECK(dbus_manager);
   dbus_manager->GetPowerManagerClient()->RemoveObserver(this);
 }
 
+void PowerDataCollector::AddSnapshot(const PowerSupplySnapshot& snapshot) {
+  while (!power_supply_data_.empty()) {
+    const PowerSupplySnapshot& first = power_supply_data_.front();
+    if (snapshot.time - first.time >
+        base::TimeDelta::FromSeconds(kSampleTimeLimitSec)) {
+      power_supply_data_.pop_front();
+    } else {
+      break;
+    }
+  }
+  power_supply_data_.push_back(snapshot);
+}
+
 PowerDataCollector::PowerSupplySnapshot::PowerSupplySnapshot()
     : time(base::TimeTicks::Now()),
       external_power(false),
       battery_percent(0) {
 }
 
 }  // namespace chromeos