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 <string>
   9 #include <vector>
  10
  11 #include "base/bind_helpers.h"
  12 #include "base/memory/ref_counted.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/observer_list.h"
  15 #include "base/threading/non_thread_safe.h"
  16
  17 namespace base {
  18 class SequencedTaskRunner;
  19 }
  20
  21 namespace device {
  22
  23 class UsbDevice;
  24
  25 // The USB service handles creating and managing an event handler thread that is
  26 // used to manage and dispatch USB events. It is also responsible for device
  27 // discovery on the system, which allows it to re-use device handles to prevent
  28 // competition for the same USB device.
  29 class UsbService : public base::NonThreadSafe {
  30  public:
  31   using GetDevicesCallback =
  32       base::Callback<void(const std::vector<scoped_refptr<UsbDevice>>&)>;
  33
  34   class Observer {
  35    public:
  36     virtual ~Observer();
  37
  38     // These events are delivered from the thread on which the UsbService object
  39     // was created.
  40     virtual void OnDeviceAdded(scoped_refptr<UsbDevice> device);
  41     virtual void OnDeviceRemoved(scoped_refptr<UsbDevice> device);
  42     // For observers that need to process device removal after others have run.
  43     // Should not depend on any other service's knowledge of connected devices.
  44     virtual void OnDeviceRemovedCleanup(scoped_refptr<UsbDevice> device);
  45
  46     // Notifies the observer that the UsbService it depends on is shutting down.
  47     virtual void WillDestroyUsbService();
  48   };
  49
  50   // The file task runner reference is used for blocking I/O operations.
  51   // Returns nullptr when initialization fails.
  52   static scoped_ptr<UsbService> Create(
  53       scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
  54
  55   virtual ~UsbService();
  56
  57   virtual scoped_refptr<UsbDevice> GetDevice(const std::string& guid) = 0;
  58
  59   // Enumerates available devices.
  60   virtual void GetDevices(const GetDevicesCallback& callback) = 0;
  61
  62   void AddObserver(Observer* observer);
  63   void RemoveObserver(Observer* observer);
  64
  65  protected:
  66   UsbService();
  67
  68   void NotifyDeviceAdded(scoped_refptr<UsbDevice> device);
  69   void NotifyDeviceRemoved(scoped_refptr<UsbDevice> device);
  70
  71   base::ObserverList<Observer, true> observer_list_;
  72
  73  private:
  74   friend void base::DeletePointer<UsbService>(UsbService* service);
  75
  76   DISALLOW_COPY_AND_ASSIGN(UsbService);
  77 };
  78
  79 }  // namespace device
  80
  81 #endif  // DEVICE_USB_USB_SERVICE_H_