Add the basic code skeleton for system info event router

chrome/browser/extensions/system_info_event_router.cc

+// 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 "chrome/browser/extensions/system_info_event_router.h"
+
+#include "base/bind.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/extensions/event_router_forwarder.h"
+#include "chrome/browser/extensions/event_names.h"
+#include "chrome/browser/extensions/api/system_info_storage/storage_info_provider.h"
+#include "chrome/common/extensions/api/experimental_system_info_storage.h"
+
+namespace extensions {
+
+using api::experimental_system_info_storage::StorageInfo;
+using api::experimental_system_info_storage::StorageUnitInfo;
+using api::experimental_system_info_storage::StorageChangeInfo;
+using content::BrowserThread;
+
+const char kSystemInfoEventPrefix[] = "experimental.systemInfo";
+const char kStorageEventPrefix[] = "experimental.systemInfo.storage";
+
+// static
+SystemInfoEventRouter* SystemInfoEventRouter::GetInstance() {
+  return Singleton<SystemInfoEventRouter>::get();
+}
+
+SystemInfoEventRouter::SystemInfoEventRouter() {
+}
+
+SystemInfoEventRouter::~SystemInfoEventRouter() {
+}
+
+void SystemInfoEventRouter::AddEventListener(const std::string& event_name) {
+  // Start watching the |event_name| event if the first event listener arrives.
+  if (event_watching_map_.find(event_name) == event_watching_map_.end()) {
+    std::string prefix(kStorageEventPrefix);
+    if (event_name.compare(0, prefix.size(), kStorageEventPrefix) == 0) {
+      // TODO (hongbo): Start watching storage device information via calling
+      // SystemMonitor::StartWatchingStorage.
+    }
+    event_watching_map_[event_name] = 1;
+    return;
+  }
+
+  // Increase the watching count.
+  event_watching_map_[event_name]++;
+}
+
+void SystemInfoEventRouter::RemoveEventListener(
+    const std::string& event_name) {
+  if (event_watching_map_.find(event_name) == event_watching_map_.end()) {
+    NOTREACHED() << "The event is NOT watched yet: " << event_name;
+    return;
+  }
+
+  if (--event_watching_map_[event_name] > 0)
+    return;
+
+  // The watching count is down to 0, it means the last event listener is
+  // removed, we need to stop watching it.
+  std::string prefix(kStorageEventPrefix);
+  if (event_name.compare(
+        0, prefix.size(), kStorageEventPrefix) == 0) {
+    // TODO(hongbo): Stop watching storage device information via calling
+    // SystemMonitor::StopWatchingStorage.
+    return;
+  }
+}
+
+// static
+bool SystemInfoEventRouter::IsSystemInfoEvent(const std::string& event_name) {
+  std::string prefix(kSystemInfoEventPrefix);
+  return event_name.compare(0, prefix.size(), prefix) == 0;
+}
+
+void SystemInfoEventRouter::OnStorageAvailableCapacityChanged(
+    const std::string& id, int64 available_capacity) {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+        base::Bind(&SystemInfoEventRouter::OnStorageAvailableCapacityChanged,
+                   base::Unretained(this), id, available_capacity));
+    return;
+  }
+
+  // We are on the UI thread now.
+  StorageChangeInfo info;
+  info.id = id;
+  info.available_capacity = static_cast<double>(available_capacity);
+
+  scoped_ptr<base::ListValue> args(new base::ListValue());
+  args->Append(info.ToValue().release());
+
+  DispatchEvent(event_names::kOnStorageAvailableCapacityChanged, args.Pass());
+}
+
+void SystemInfoEventRouter::OnRemovableStorageAttached(const std::string& id,
+    const string16& name,  const FilePath::StringType& location) {
+  // TODO(hongbo): Handle storage device arrival/removal event.
+}
+
+void SystemInfoEventRouter::OnRemovableStorageDetached(const std::string& id) {
+  // TODO(hongbo): Same as above.
+}
+
+void SystemInfoEventRouter::DispatchEvent(const std::string& event_name,
+                                          scoped_ptr<base::ListValue> args) {
+  g_browser_process->extension_event_router_forwarder()->
+      BroadcastEventToRenderers(event_name, args.Pass(), GURL());
+}
+
+}  // namespace extensions