content/browser/geolocation/wifi_data_provider.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // A wifi data provider provides wifi data from the device that is used by a
   6 // NetworkLocationProvider to obtain a position fix. We use a singleton
   7 // instance of the wifi data provider, which is used by multiple
   8 // NetworkLocationProvider objects.
   9 //
  10 // This file provides WifiDataProvider, which provides static methods to
  11 // access the singleton instance. The singleton instance uses a private
  12 // implementation to abstract across platforms and also to allow mock providers
  13 // to be used for testing.
  14 //
  15 // This file also provides WifiDataProviderImplBase, a base class which
  16 // provides common functionality for the private implementations.
  17
  18 #ifndef CONTENT_BROWSER_GEOLOCATION_WIFI_DATA_PROVIDER_H_
  19 #define CONTENT_BROWSER_GEOLOCATION_WIFI_DATA_PROVIDER_H_
  20
  21 #include <set>
  22
  23 #include "base/basictypes.h"
  24 #include "base/bind.h"
  25 #include "base/callback.h"
  26 #include "base/memory/ref_counted.h"
  27 #include "base/message_loop/message_loop.h"
  28 #include "base/strings/string16.h"
  29 #include "base/strings/string_util.h"
  30 #include "content/browser/geolocation/wifi_data.h"
  31 #include "content/common/content_export.h"
  32
  33 namespace content {
  34
  35 class WifiDataProvider;
  36
  37 // See class WifiDataProvider for the public client API.
  38 // WifiDataProvider uses containment to hide platform-specific implementation
  39 // details from common code. This class provides common functionality for these
  40 // contained implementation classes. This is a modified pimpl pattern.
  41 class CONTENT_EXPORT WifiDataProviderImplBase
  42     : public base::RefCountedThreadSafe<WifiDataProviderImplBase> {
  43  public:
  44   WifiDataProviderImplBase();
  45
  46   // Tells the provider to start looking for data. Callbacks will start
  47   // receiving notifications after this call.
  48   virtual void StartDataProvider() = 0;
  49
  50   // Tells the provider to stop looking for data. Callbacks will stop
  51   // receiving notifications after this call.
  52   virtual void StopDataProvider() = 0;
  53
  54   // Provides whatever data the provider has, which may be nothing. Return
  55   // value indicates whether this is all the data the provider could ever
  56   // obtain.
  57   virtual bool GetData(WifiData* data) = 0;
  58
  59   // Sets the container of this class, which is of type WifiDataProvider.
  60   // This is required to pass as a parameter when calling a callback.
  61   void SetContainer(WifiDataProvider* container);
  62
  63   typedef base::Callback<void(WifiDataProvider*)> WifiDataUpdateCallback;
  64
  65   void AddCallback(WifiDataUpdateCallback* callback);
  66
  67   bool RemoveCallback(WifiDataUpdateCallback* callback);
  68
  69   bool has_callbacks() const;
  70
  71  protected:
  72   friend class base::RefCountedThreadSafe<WifiDataProviderImplBase>;
  73   virtual ~WifiDataProviderImplBase();
  74
  75   typedef std::set<WifiDataUpdateCallback*> CallbackSet;
  76
  77   // Runs all callbacks via a posted task, so we can unwind callstack here and
  78   // avoid client reentrancy.
  79   void RunCallbacks();
  80
  81   bool CalledOnClientThread() const;
  82
  83   base::MessageLoop* client_loop() const;
  84
  85  private:
  86   void DoRunCallbacks();
  87
  88   WifiDataProvider* container_;
  89
  90   // Reference to the client's message loop. All callbacks should happen in this
  91   // context.
  92   base::MessageLoop* client_loop_;
  93
  94   CallbackSet callbacks_;
  95
  96   DISALLOW_COPY_AND_ASSIGN(WifiDataProviderImplBase);
  97 };
  98
  99 // A wifi data provider
 100 //
 101 // We use a singleton instance of this class which is shared by multiple network
 102 // location providers. These location providers access the instance through the
 103 // Register and Unregister methods.
 104 class CONTENT_EXPORT WifiDataProvider {
 105  public:
 106   // Sets the factory function which will be used by Register to create the
 107   // implementation used by the singleton instance. This factory approach is
 108   // used both to abstract accross platform-specific implementations and to
 109   // inject mock implementations for testing.
 110   typedef WifiDataProviderImplBase* (*ImplFactoryFunction)(void);
 111   static void SetFactory(ImplFactoryFunction factory_function_in);
 112
 113   // Resets the factory function to the default.
 114   static void ResetFactory();
 115
 116   typedef base::Callback<void(WifiDataProvider*)> WifiDataUpdateCallback;
 117
 118   // Registers a callback, which will be run whenever new data is available.
 119   // Instantiates the singleton if necessary, and always returns it.
 120   static WifiDataProvider* Register(WifiDataUpdateCallback* callback);
 121
 122   // Removes a callback. If this is the last callback, deletes the singleton
 123   // instance. Return value indicates success.
 124   static bool Unregister(WifiDataUpdateCallback* callback);
 125
 126   // Provides whatever data the provider has, which may be nothing. Return
 127   // value indicates whether this is all the data the provider could ever
 128   // obtain.
 129   bool GetData(WifiData* data);
 130
 131  private:
 132   // Private constructor and destructor, callers access singleton through
 133   // Register and Unregister.
 134   WifiDataProvider();
 135   virtual ~WifiDataProvider();
 136
 137   void AddCallback(WifiDataUpdateCallback* callback);
 138   bool RemoveCallback(WifiDataUpdateCallback* callback);
 139   bool has_callbacks() const;
 140
 141   void StartDataProvider();
 142   void StopDataProvider();
 143
 144   static WifiDataProviderImplBase* DefaultFactoryFunction();
 145
 146   // The singleton-like instance of this class. (Not 'true' singleton, as it
 147   // may go through multiple create/destroy/create cycles per process instance,
 148   // e.g. when under test).
 149   static WifiDataProvider* instance_;
 150
 151   // The factory function used to create the singleton instance.
 152   static ImplFactoryFunction factory_function_;
 153
 154   // The internal implementation.
 155   scoped_refptr<WifiDataProviderImplBase> impl_;
 156
 157   DISALLOW_COPY_AND_ASSIGN(WifiDataProvider);
 158 };
 159
 160 }  // namespace content
 161
 162 #endif  // CONTENT_BROWSER_GEOLOCATION_WIFI_DATA_PROVIDER_H_