content/browser/device_sensors/data_fetcher_shared_memory_base.h

   1 // Copyright 2014 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 #ifndef CONTENT_BROWSER_DEVICE_SENSORS_DATA_FETCHER_SHARED_MEMORY_BASE_H_
   6 #define CONTENT_BROWSER_DEVICE_SENSORS_DATA_FETCHER_SHARED_MEMORY_BASE_H_
   7
   8 #include <map>
   9
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/memory/shared_memory.h"
  12 #include "base/message_loop/message_loop.h"
  13 #include "content/browser/device_sensors/inertial_sensor_consts.h"
  14 #include "content/common/content_export.h"
  15
  16 namespace content {
  17
  18 // Sensor data fetchers should derive from this base class and implement
  19 // the abstract Start() and Stop() methods.
  20 // If the fetcher requires polling it should also implement IsPolling()
  21 // to return true and the Fetch() method which will be called from the
  22 // polling thread to fetch data at regular intervals.
  23 class CONTENT_EXPORT DataFetcherSharedMemoryBase {
  24  public:
  25   // Starts updating the shared memory buffer with sensor data at
  26   // regular intervals. Returns true if the relevant sensors could
  27   // be successfully activated.
  28   bool StartFetchingDeviceData(ConsumerType consumer_type);
  29
  30   // Stops updating the shared memory buffer. Returns true if the
  31   // relevant sensors could be successfully deactivated.
  32   bool StopFetchingDeviceData(ConsumerType consumer_type);
  33
  34   // Should be called before destruction to make sure all active
  35   // sensors are unregistered.
  36   void StopFetchingAllDeviceData();
  37
  38   // Returns the shared memory handle of the device sensor data
  39   // duplicated into the given process. This method should only be
  40   // called after a call to StartFetchingDeviceData method with
  41   // corresponding |consumer_type| parameter.
  42   base::SharedMemoryHandle GetSharedMemoryHandleForProcess(
  43       ConsumerType consumer_type, base::ProcessHandle process);
  44
  45   enum FetcherType {
  46     // Fetcher runs on the same thread as its creator.
  47     FETCHER_TYPE_DEFAULT,
  48     // Fetcher runs on a separate thread calling |Fetch()| at regular intervals.
  49     FETCHER_TYPE_POLLING_CALLBACK,
  50     // Fetcher runs on a separate thread, but no callbacks are executed.
  51     FETCHER_TYPE_SEPARATE_THREAD
  52   };
  53
  54  protected:
  55   class PollingThread;
  56
  57   DataFetcherSharedMemoryBase();
  58   virtual ~DataFetcherSharedMemoryBase();
  59
  60   // Returns the message loop of the polling thread.
  61   // Returns NULL if there is no polling thread.
  62   base::MessageLoop* GetPollingMessageLoop() const;
  63
  64   // If IsPolling() is true this method is called from the |polling_thread_|
  65   // at regular intervals.
  66   virtual void Fetch(unsigned consumer_bitmask);
  67
  68   // Returns the type of thread this fetcher runs on.
  69   virtual FetcherType GetType() const;
  70
  71   // Returns the sensor sampling interval. In particular if this fetcher
  72   // GetType() == FETCHER_TYPE_POLLING_CALLBACK the interval between
  73   // successive calls to Fetch().
  74   virtual base::TimeDelta GetInterval() const;
  75
  76   // Start() method should call InitSharedMemoryBuffer() to get the shared
  77   // memory pointer. If IsPolling() is true both Start() and Stop() methods
  78   // are called from the |polling_thread_|.
  79   virtual bool Start(ConsumerType consumer_type, void* buffer) = 0;
  80   virtual bool Stop(ConsumerType consumer_type) = 0;
  81
  82   bool IsPollingTimerRunningForTesting() const;
  83
  84  private:
  85   bool InitAndStartPollingThreadIfNecessary();
  86   base::SharedMemory* GetSharedMemory(ConsumerType consumer_type);
  87   void* GetSharedMemoryBuffer(ConsumerType consumer_type);
  88
  89   unsigned started_consumers_;
  90
  91   scoped_ptr<PollingThread> polling_thread_;
  92
  93   // Owning pointers. Objects in the map are deleted in dtor.
  94   typedef std::map<ConsumerType, base::SharedMemory*> SharedMemoryMap;
  95   SharedMemoryMap shared_memory_map_;
  96
  97   DISALLOW_COPY_AND_ASSIGN(DataFetcherSharedMemoryBase);
  98 };
  99
 100 }  // namespace content
 101
 102 #endif  // CONTENT_BROWSER_DEVICE_SENSORS_DATA_FETCHER_SHARED_MEMORY_BASE_H_