content/browser/device_orientation/data_fetcher_shared_memory_base.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 #ifndef CONTENT_BROWSER_DEVICE_ORIENTATION_DATA_FETCHER_SHARED_MEMORY_BASE_H_
   6 #define CONTENT_BROWSER_DEVICE_ORIENTATION_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_orientation/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
  26   // Starts updating the shared memory buffer with sensor data at
  27   // regular intervals. Returns true if the relevant sensors could
  28   // be successfully activated.
  29   bool StartFetchingDeviceData(ConsumerType consumer_type);
  30
  31   // Stops updating the shared memory buffer. Returns true if the
  32   // relevant sensors could be successfully deactivated.
  33   bool StopFetchingDeviceData(ConsumerType consumer_type);
  34
  35   // Returns the shared memory handle of the device sensor data
  36   // duplicated into the given process. This method should only be
  37   // called after a call to StartFetchingDeviceData method with
  38   // corresponding |consumer_type| parameter.
  39   base::SharedMemoryHandle GetSharedMemoryHandleForProcess(
  40       ConsumerType consumer_type, base::ProcessHandle process);
  41
  42   enum FetcherType {
  43     // Fetcher runs on the same thread as its creator.
  44     FETCHER_TYPE_DEFAULT,
  45     // Fetcher runs on a separate thread calling |Fetch()| at regular intervals.
  46     FETCHER_TYPE_POLLING_CALLBACK,
  47     // Fetcher runs on a separate thread, but no callbacks are executed.
  48     FETCHER_TYPE_SEPARATE_THREAD
  49   };
  50
  51  protected:
  52   class PollingThread;
  53
  54   DataFetcherSharedMemoryBase();
  55   virtual ~DataFetcherSharedMemoryBase();
  56
  57   // Returns the message loop of the polling thread.
  58   // Returns NULL if there is no polling thread.
  59   base::MessageLoop* GetPollingMessageLoop() const;
  60
  61   // If IsPolling() is true this method is called from the |polling_thread_|
  62   // at regular intervals.
  63   virtual void Fetch(unsigned consumer_bitmask);
  64
  65   // Returns the type of thread this fetcher runs on.
  66   virtual FetcherType GetType() const;
  67
  68   // Returns the sensor sampling interval. In particular if this fetcher
  69   // GetType() == FETCHER_TYPE_POLLING_CALLBACK the interval between
  70   // successive calls to Fetch().
  71   virtual base::TimeDelta GetInterval() const;
  72
  73   // Start() method should call InitSharedMemoryBuffer() to get the shared
  74   // memory pointer. If IsPolling() is true both Start() and Stop() methods
  75   // are called from the |polling_thread_|.
  76   virtual bool Start(ConsumerType consumer_type, void* buffer) = 0;
  77   virtual bool Stop(ConsumerType consumer_type) = 0;
  78
  79   bool IsPollingTimerRunningForTesting() const;
  80
  81  private:
  82   bool InitAndStartPollingThreadIfNecessary();
  83   base::SharedMemory* GetSharedMemory(ConsumerType consumer_type);
  84   void* GetSharedMemoryBuffer(ConsumerType consumer_type);
  85
  86   unsigned started_consumers_;
  87
  88   scoped_ptr<PollingThread> polling_thread_;
  89
  90   // Owning pointers. Objects in the map are deleted in dtor.
  91   typedef std::map<ConsumerType, base::SharedMemory*> SharedMemoryMap;
  92   SharedMemoryMap shared_memory_map_;
  93
  94   DISALLOW_COPY_AND_ASSIGN(DataFetcherSharedMemoryBase);
  95 };
  96
  97 }
  98
  99 #endif  // CONTENT_BROWSER_DEVICE_ORIENTATION_DATA_FETCHER_SHARED_MEMORY_BASE_H_