// Copyright 2008, Google Inc.
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#ifndef GEARS_GEOLOCATION_EMPTY_DEVICE_DATA_PROVIDER_H__
#define GEARS_GEOLOCATION_EMPTY_DEVICE_DATA_PROVIDER_H__

#include "gears/geolocation/device_data_provider.h"

// An implementation of DeviceDataProviderBase that does not provide any data.
// Used on platforms where a given data type is not available.

template<typename DataType>
class EmptyDeviceDataProvider : public DeviceDataProviderBase<DataType> {
 public:
  // Allow DeviceDataProviderBase<DataType>::Create() to access our private
  // constructor.
  friend class DeviceDataProviderBase<DataType>;
  // DeviceDataProviderBase<DataType> implementation.
  virtual bool GetData(DataType *data) {
    assert(data);
    // This is all the data we can get - nothing.
    return true;
  }
 private:
  // Private constructor and destructor, callers must use Register and
  // Unregister.
  EmptyDeviceDataProvider() {}
  virtual ~EmptyDeviceDataProvider() {}
  DISALLOW_EVIL_CONSTRUCTORS(EmptyDeviceDataProvider);
};

#endif  // GEARS_GEOLOCATION_EMPTY_DEVICE_DATA_PROVIDER_H__