content/browser/geolocation/location_provider.h

   1 // Copyright (c) 2012 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 location provider provides position information from a particular source
   6 // (GPS, network etc).
   7 //
   8 // This file declares a base class to be used by all location providers.
   9 // Primarily, this class declares interface methods to be implemented by
  10 // derived classes.
  11
  12 #ifndef CONTENT_BROWSER_GEOLOCATION_LOCATION_PROVIDER_H_
  13 #define CONTENT_BROWSER_GEOLOCATION_LOCATION_PROVIDER_H_
  14
  15 #include <map>
  16
  17 #include "base/string16.h"
  18 #include "base/threading/non_thread_safe.h"
  19 #include "content/common/content_export.h"
  20
  21 class GURL;
  22
  23 namespace net {
  24 class URLRequestContextGetter;
  25 }
  26
  27 namespace content {
  28 class AccessTokenStore;
  29 struct Geoposition;
  30
  31 // The base class used by all location providers.
  32 class CONTENT_EXPORT LocationProviderBase
  33     : NON_EXPORTED_BASE(public base::NonThreadSafe) {
  34  public:
  35   // Clients of the location provider must implement this interface. All call-
  36   // backs to this interface will happen in the context of the thread on which
  37   // the location provider was created.
  38   class CONTENT_EXPORT ListenerInterface {
  39    public:
  40     // Used to inform listener that a new position fix is available or that a
  41     // fatal error has occurred. Providers should call this for new listeners
  42     // as soon as a position is available.
  43     virtual void LocationUpdateAvailable(LocationProviderBase* provider) = 0;
  44
  45    protected:
  46     virtual ~ListenerInterface() {}
  47   };
  48
  49   virtual ~LocationProviderBase();
  50
  51   // Registers a listener, which will be called back on
  52   // ListenerInterface::LocationUpdateAvailable as soon as a position is
  53   // available and again whenever a new position is available. Ref counts the
  54   // listener to handle multiple calls to this method.
  55   void RegisterListener(ListenerInterface* listener);
  56   // Unregisters a listener. Unrefs the listener to handle multiple calls to
  57   // this method. Once the ref count reaches zero, the listener is removed and
  58   // once this method returns, no further calls to
  59   // ListenerInterface::LocationUpdateAvailable will be made for this listener.
  60   // It may block if a callback is in progress.
  61   void UnregisterListener(ListenerInterface* listener);
  62
  63   // Interface methods
  64   // StartProvider maybe called multiple times, e.g. to alter the
  65   // |high_accuracy| setting. Returns false if a fatal error was encountered
  66   // which prevented the provider from starting.
  67   virtual bool StartProvider(bool high_accuracy) = 0;
  68   virtual void StopProvider() = 0;
  69   // Gets the current best position estimate.
  70   virtual void GetPosition(Geoposition* position) = 0;
  71   // Provides a hint to the provider that new location data is needed as soon
  72   // as possible. Default implementation does nothing.
  73   virtual void UpdatePosition() {}
  74   // Delegated to the provider by GeolocationArbitrator. See the corresponding
  75   // method on that class for more details.
  76   virtual void OnPermissionGranted() {}
  77
  78   bool has_listeners() const;
  79
  80  protected:
  81   LocationProviderBase();
  82
  83   // Inform listeners that a new position or error is available, using
  84   // LocationUpdateAvailable.
  85   void UpdateListeners();
  86
  87  private:
  88   // The listeners registered to this provider. For each listener, we store a
  89   // ref count.
  90   typedef std::map<ListenerInterface*, int> ListenerMap;
  91   ListenerMap listeners_;
  92 };
  93
  94 // Factory functions for the various types of location provider to abstract
  95 // over the platform-dependent implementations.
  96 CONTENT_EXPORT LocationProviderBase* NewNetworkLocationProvider(
  97     AccessTokenStore* access_token_store,
  98     net::URLRequestContextGetter* context,
  99     const GURL& url,
 100     const string16& access_token);
 101 LocationProviderBase* NewSystemLocationProvider();
 102
 103 }  // namespace content
 104
 105 #endif  // CONTENT_BROWSER_GEOLOCATION_LOCATION_PROVIDER_H_