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   // Returns the shared memory handle of the device sensor data
  35   // duplicated into the given process. This method should only be
  36   // called after a call to StartFetchingDeviceData method with
  37   // corresponding |consumer_type| parameter.
  38   base::SharedMemoryHandle GetSharedMemoryHandleForProcess(
  39       ConsumerType consumer_type, base::ProcessHandle process);
  40
  41   enum FetcherType {
  42     // Fetcher runs on the same thread as its creator.
  43     FETCHER_TYPE_DEFAULT,
  44     // Fetcher runs on a separate thread calling |Fetch()| at regular intervals.
  45     FETCHER_TYPE_POLLING_CALLBACK,
  46     // Fetcher runs on a separate thread, but no callbacks are executed.
  47     FETCHER_TYPE_SEPARATE_THREAD
  48   };
  49
  50  protected:
  51   class PollingThread;
  52
  53   DataFetcherSharedMemoryBase();
  54   virtual ~DataFetcherSharedMemoryBase();
  55
  56   // Returns the message loop of the polling thread.
  57   // Returns NULL if there is no polling thread.
  58   base::MessageLoop* GetPollingMessageLoop() const;
  59
  60   // If IsPolling() is true this method is called from the |polling_thread_|
  61   // at regular intervals.
  62   virtual void Fetch(unsigned consumer_bitmask);
  63
  64   // Returns the type of thread this fetcher runs on.
  65   virtual FetcherType GetType() const;
  66
  67   // Returns the sensor sampling interval. In particular if this fetcher
  68   // GetType() == FETCHER_TYPE_POLLING_CALLBACK the interval between
  69   // successive calls to Fetch().
  70   virtual base::TimeDelta GetInterval() const;
  71
  72   // Start() method should call InitSharedMemoryBuffer() to get the shared
  73   // memory pointer. If IsPolling() is true both Start() and Stop() methods
  74   // are called from the |polling_thread_|.
  75   virtual bool Start(ConsumerType consumer_type, void* buffer) = 0;
  76   virtual bool Stop(ConsumerType consumer_type) = 0;
  77
  78   bool IsPollingTimerRunningForTesting() const;
  79
  80  private:
  81   bool InitAndStartPollingThreadIfNecessary();
  82   base::SharedMemory* GetSharedMemory(ConsumerType consumer_type);
  83   void* GetSharedMemoryBuffer(ConsumerType consumer_type);
  84
  85   unsigned started_consumers_;
  86
  87   scoped_ptr<PollingThread> polling_thread_;
  88
  89   // Owning pointers. Objects in the map are deleted in dtor.
  90   typedef std::map<ConsumerType, base::SharedMemory*> SharedMemoryMap;
  91   SharedMemoryMap shared_memory_map_;
  92
  93   DISALLOW_COPY_AND_ASSIGN(DataFetcherSharedMemoryBase);
  94 };
  95
  96 }  // namespace content
  97
  98 #endif  // CONTENT_BROWSER_DEVICE_SENSORS_DATA_FETCHER_SHARED_MEMORY_BASE_H_