[WIP] attempt to allow chrome OS to inject its wifi data provider

content/browser/geolocation/device_data_provider.h

-// Copyright (c) 2011 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.
-
-// A device data provider provides data from the device that is used by a
-// NetworkLocationProvider to obtain a position fix. This data may be either
-// cell radio data or wifi data. For a given type of data, we use a singleton
-// instance of the device data provider, which is used by multiple
-// NetworkLocationProvider objects.
-//
-// This file providers DeviceDataProvider, which provides static methods to
-// access the singleton instance. The singleton instance uses a private
-// implementation to abstract across platforms and also to allow mock providers
-// to be used for testing.
-//
-// This file also provides DeviceDataProviderImplBase, a base class which
-// provides commom functionality for the private implementations.
-//
-// This file also declares the data structures used to represent cell radio data
-// and wifi data.
-
-#ifndef CONTENT_BROWSER_GEOLOCATION_DEVICE_DATA_PROVIDER_H_
-#define CONTENT_BROWSER_GEOLOCATION_DEVICE_DATA_PROVIDER_H_
-#pragma once
-
-#include <set>
-
-#include "base/basictypes.h"
-#include "base/bind.h"
-#include "base/memory/ref_counted.h"
-#include "base/message_loop.h"
-#include "base/string16.h"
-#include "base/string_util.h"
-#include "base/threading/non_thread_safe.h"
-#include "content/common/content_export.h"
-
-// Wifi data relating to a single access point.
-struct CONTENT_EXPORT AccessPointData {
-  AccessPointData();
-  ~AccessPointData();
-
-  // MAC address, formatted as per MacAddressAsString16.
-  string16 mac_address;
-  int radio_signal_strength;  // Measured in dBm
-  int channel;
-  int signal_to_noise;  // Ratio in dB
-  string16 ssid;   // Network identifier
-};
-
-// This is to allow AccessPointData to be used in std::set. We order
-// lexicographically by MAC address.
-struct AccessPointDataLess {
-  bool operator()(const AccessPointData& data1,
-                  const AccessPointData& data2) const {
-    return data1.mac_address < data2.mac_address;
-  }
-};
-
-// All data for wifi.
-struct CONTENT_EXPORT WifiData {
-  WifiData();
-  ~WifiData();
-
-  // Determines whether a new set of WiFi data differs significantly from this.
-  bool DiffersSignificantly(const WifiData& other) const;
-
-  // Store access points as a set, sorted by MAC address. This allows quick
-  // comparison of sets for detecting changes and for caching.
-  typedef std::set<AccessPointData, AccessPointDataLess> AccessPointDataSet;
-  AccessPointDataSet access_point_data;
-};
-
-template<typename DataType>
-class DeviceDataProvider;
-
-// This class just exists to work-around MSVC2005 not being able to have a
-// template class implement RefCountedThreadSafe
-class CONTENT_EXPORT DeviceDataProviderImplBaseHack
-    : public base::RefCountedThreadSafe<DeviceDataProviderImplBaseHack> {
- protected:
-  friend class base::RefCountedThreadSafe<DeviceDataProviderImplBaseHack>;
-  virtual ~DeviceDataProviderImplBaseHack() {}
-};
-
-// See class DeviceDataProvider for the public client API.
-// DeviceDataProvider uses containment to hide platform-specific implementation
-// details from common code. This class provides common functionality for these
-// contained implementation classes. This is a modified pimpl pattern: this
-// class needs to be in the public header due to use of templating.
-template<typename DataType>
-class DeviceDataProviderImplBase : public DeviceDataProviderImplBaseHack {
- public:
-  DeviceDataProviderImplBase()
-      : container_(NULL), client_loop_(MessageLoop::current()) {
-    DCHECK(client_loop_);
-  }
-
-  virtual bool StartDataProvider() = 0;
-  virtual void StopDataProvider() = 0;
-  virtual bool GetData(DataType* data) = 0;
-
-  // Sets the container of this class, which is of type DeviceDataProvider.
-  // This is required to pass as a parameter when making the callback to
-  // listeners.
-  void SetContainer(DeviceDataProvider<DataType>* container) {
-    DCHECK(CalledOnClientThread());
-    container_ = container;
-  }
-
-  typedef typename DeviceDataProvider<DataType>::ListenerInterface
-          ListenerInterface;
-  void AddListener(ListenerInterface* listener) {
-    DCHECK(CalledOnClientThread());
-    listeners_.insert(listener);
-  }
-  bool RemoveListener(ListenerInterface* listener) {
-    DCHECK(CalledOnClientThread());
-    return listeners_.erase(listener) == 1;
-  }
-
-  bool has_listeners() const {
-    DCHECK(CalledOnClientThread());
-    return !listeners_.empty();
-  }
-
- protected:
-  virtual ~DeviceDataProviderImplBase() {
-    DCHECK(CalledOnClientThread());
-  }
-
-  // Calls DeviceDataUpdateAvailable() on all registered listeners.
-  typedef std::set<ListenerInterface*> ListenersSet;
-  void NotifyListeners() {
-    // Always make the notify callback via a posted task, so we can unwind
-    // callstack here and make callback without causing client re-entrancy.
-    client_loop_->PostTask(FROM_HERE, base::Bind(
-        &DeviceDataProviderImplBase<DataType>::NotifyListenersInClientLoop,
-        this));
-  }
-
-  bool CalledOnClientThread() const {
-    return MessageLoop::current() == this->client_loop_;
-  }
-
-  MessageLoop* client_loop() const {
-    return client_loop_;
-  }
-
- private:
-  void NotifyListenersInClientLoop() {
-    DCHECK(CalledOnClientThread());
-    // It's possible that all the listeners (and the container) went away
-    // whilst this task was pending. This is fine; the loop will be a no-op.
-    typename ListenersSet::const_iterator iter = listeners_.begin();
-    while (iter != listeners_.end()) {
-      ListenerInterface* listener = *iter;
-      ++iter;  // Advance iter before callback, in case listener unregisters.
-      listener->DeviceDataUpdateAvailable(container_);
-    }
-  }
-
-  DeviceDataProvider<DataType>* container_;
-
-  // Reference to the client's message loop, all callbacks and access to
-  // the listeners_ member should happen in this context.
-  MessageLoop* client_loop_;
-
-  ListenersSet listeners_;
-
-  DISALLOW_COPY_AND_ASSIGN(DeviceDataProviderImplBase);
-};
-
-typedef DeviceDataProviderImplBase<WifiData> WifiDataProviderImplBase;
-
-// A device data provider
-//
-// We use a singleton instance of this class which is shared by multiple network
-// location providers. These location providers access the instance through the
-// Register and Unregister methods.
-template<typename DataType>
-class DeviceDataProvider : public base::NonThreadSafe {
- public:
-  // Interface to be implemented by listeners to a device data provider.
-  class ListenerInterface {
-   public:
-    // Will be called in the context of the thread that called Register().
-    virtual void DeviceDataUpdateAvailable(
-        DeviceDataProvider<DataType>* provider) = 0;
-    virtual ~ListenerInterface() {}
-  };
-
-  // Sets the factory function which will be used by Register to create the
-  // implementation used by the singleton instance. This factory approach is
-  // used to abastract accross both platform-specific implementation and to
-  // inject mock implementations for testing.
-  typedef DeviceDataProviderImplBase<DataType>* (*ImplFactoryFunction)(void);
-  static void SetFactory(ImplFactoryFunction factory_function_in) {
-    factory_function_ = factory_function_in;
-  }
-
-  static void ResetFactory() {
-    factory_function_ = DefaultFactoryFunction;
-  }
-
-  // Adds a listener, which will be called back with DeviceDataUpdateAvailable
-  // whenever new data is available. Returns the singleton instance.
-  static DeviceDataProvider* Register(ListenerInterface* listener) {
-    bool need_to_start_thread = false;
-    if (!instance_) {
-      instance_ = new DeviceDataProvider();
-      need_to_start_thread = true;
-    }
-    DCHECK(instance_);
-    DCHECK(instance_->CalledOnValidThread());
-    instance_->AddListener(listener);
-    // Start the provider after adding the listener, to avoid any race in
-    // it receiving an early callback.
-    if (need_to_start_thread) {
-      bool started = instance_->StartDataProvider();
-      DCHECK(started);
-    }
-    return instance_;
-  }
-
-  // Removes a listener. If this is the last listener, deletes the singleton
-  // instance. Return value indicates success.
-  static bool Unregister(ListenerInterface* listener) {
-    DCHECK(instance_);
-    DCHECK(instance_->CalledOnValidThread());
-    DCHECK(instance_->has_listeners());
-    if (!instance_->RemoveListener(listener)) {
-      return false;
-    }
-    if (!instance_->has_listeners()) {
-      // Must stop the provider (and any implementation threads) before
-      // destroying to avoid any race conditions in access to the provider in
-      // the destructor chain.
-      instance_->StopDataProvider();
-      delete instance_;
-      instance_ = NULL;
-    }
-    return true;
-  }
-
-  // Provides whatever data the provider has, which may be nothing. Return
-  // value indicates whether this is all the data the provider could ever
-  // obtain.
-  bool GetData(DataType* data) {
-    DCHECK(this->CalledOnValidThread());
-    return impl_->GetData(data);
-  }
-
- private:
-  // Private constructor and destructor, callers access singleton through
-  // Register and Unregister.
-  DeviceDataProvider() {
-    DCHECK(factory_function_);
-    impl_ = (*factory_function_)();
-    DCHECK(impl_);
-    impl_->SetContainer(this);
-  }
-  virtual ~DeviceDataProvider() {
-    DCHECK(impl_);
-    impl_->SetContainer(NULL);
-  }
-
-  void AddListener(ListenerInterface* listener) {
-    impl_->AddListener(listener);
-  }
-
-  bool RemoveListener(ListenerInterface* listener) {
-    return impl_->RemoveListener(listener);
-  }
-
-  bool has_listeners() const {
-    return impl_->has_listeners();
-  }
-
-  bool StartDataProvider() {
-    return impl_->StartDataProvider();
-  }
-
-  void StopDataProvider() {
-    impl_->StopDataProvider();
-  }
-
-  CONTENT_EXPORT static DeviceDataProviderImplBase<DataType>*
-      DefaultFactoryFunction();
-
-  // The singleton-like instance of this class. (Not 'true' singleton, as it
-  // may go through multiple create/destroy/create cycles per process instance,
-  // e.g. when under test).
-  CONTENT_EXPORT static DeviceDataProvider* instance_;
-
-  // The factory function used to create the singleton instance.
-  CONTENT_EXPORT static ImplFactoryFunction factory_function_;
-
-  // The internal implementation.
-  scoped_refptr<DeviceDataProviderImplBase<DataType> > impl_;
-
-  DISALLOW_COPY_AND_ASSIGN(DeviceDataProvider);
-};
-
-typedef DeviceDataProvider<WifiData> WifiDataProvider;
-
-#endif  // CONTENT_BROWSER_GEOLOCATION_DEVICE_DATA_PROVIDER_H_