device/usb/usb_service.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 DEVICE_USB_USB_SERVICE_H_
   6 #define DEVICE_USB_USB_SERVICE_H_
   7
   8 #include <vector>
   9
  10 #include "base/bind_helpers.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/observer_list.h"
  14 #include "base/threading/non_thread_safe.h"
  15
  16 namespace base {
  17 class SequencedTaskRunner;
  18 }
  19
  20 namespace device {
  21
  22 class UsbDevice;
  23
  24 // The USB service handles creating and managing an event handler thread that is
  25 // used to manage and dispatch USB events. It is also responsible for device
  26 // discovery on the system, which allows it to re-use device handles to prevent
  27 // competition for the same USB device.
  28 class UsbService : public base::NonThreadSafe {
  29  public:
  30   using GetDevicesCallback =
  31       base::Callback<void(const std::vector<scoped_refptr<UsbDevice>>&)>;
  32
  33   class Observer {
  34    public:
  35     // These events are delivered from the thread on which the UsbService object
  36     // was created.
  37     virtual void OnDeviceAdded(scoped_refptr<UsbDevice> device);
  38     virtual void OnDeviceRemoved(scoped_refptr<UsbDevice> device);
  39     // For observers that need to process device removal after others have run.
  40     // Should not depend on any other service's knowledge of connected devices.
  41     virtual void OnDeviceRemovedCleanup(scoped_refptr<UsbDevice> device);
  42   };
  43
  44   // The file task runner reference is used for blocking I/O operations.
  45   // Returns NULL when initialization fails.
  46   static UsbService* GetInstance(
  47       scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
  48
  49   virtual scoped_refptr<UsbDevice> GetDeviceById(uint32 unique_id) = 0;
  50
  51   // Enumerates available devices.
  52   virtual void GetDevices(const GetDevicesCallback& callback) = 0;
  53
  54   void AddObserver(Observer* observer);
  55   void RemoveObserver(Observer* observer);
  56
  57  protected:
  58   UsbService();
  59   virtual ~UsbService();
  60
  61   void NotifyDeviceAdded(scoped_refptr<UsbDevice> device);
  62   void NotifyDeviceRemoved(scoped_refptr<UsbDevice> device);
  63
  64   ObserverList<Observer, true> observer_list_;
  65
  66  private:
  67   friend void base::DeletePointer<UsbService>(UsbService* service);
  68
  69   DISALLOW_COPY_AND_ASSIGN(UsbService);
  70 };
  71
  72 }  // namespace device
  73
  74 #endif  // DEVICE_USB_USB_SERVICE_H_