device/usb/usb_service.h

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef DEVICE_USB_USB_SERVICE_H_
#define DEVICE_USB_USB_SERVICE_H_

#include <vector>

#include "base/memory/ref_counted.h"
#include "base/memory/scoped_ptr.h"
#include "base/observer_list.h"
#include "base/threading/non_thread_safe.h"

namespace base {
class SingleThreadTaskRunner;
}

namespace device {

class UsbDevice;

// The USB service handles creating and managing an event handler thread that is
// used to manage and dispatch USB events. It is also responsible for device
// discovery on the system, which allows it to re-use device handles to prevent
// competition for the same USB device.
//
// All functions on this object must be called from a thread with a
// MessageLoopForIO (for example, BrowserThread::FILE).
class UsbService : public base::NonThreadSafe {
 public:
  class Observer {
   public:
    // These events are delivered from the thread on which the UsbService object
    // was created.
    virtual void OnDeviceAdded(scoped_refptr<UsbDevice> device);
    virtual void OnDeviceRemoved(scoped_refptr<UsbDevice> device);
    // For observers that need to process device removal after others have run.
    // Should not depend on any other service's knowledge of connected devices.
    virtual void OnDeviceRemovedCleanup(scoped_refptr<UsbDevice> device);
  };

  // The UI task runner reference is used to talk to the PermissionBrokerClient
  // on ChromeOS (UI thread). Returns NULL when initialization fails.
  static UsbService* GetInstance(
      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);

  static void SetInstanceForTest(UsbService* instance);

  virtual scoped_refptr<UsbDevice> GetDeviceById(uint32 unique_id) = 0;

  // Get all of the devices attached to the system, inserting them into
  // |devices|. Clears |devices| before use. The result will be sorted by id
  // in increasing order.
  virtual void GetDevices(std::vector<scoped_refptr<UsbDevice> >* devices) = 0;

  void AddObserver(Observer* observer);
  void RemoveObserver(Observer* observer);

 protected:
  UsbService();
  virtual ~UsbService();

  void NotifyDeviceAdded(scoped_refptr<UsbDevice> device);
  void NotifyDeviceRemoved(scoped_refptr<UsbDevice> device);

  ObserverList<Observer, true> observer_list_;

 private:
  class Destroyer;

  DISALLOW_COPY_AND_ASSIGN(UsbService);
};

}  // namespace device

#endif  // DEVICE_USB_USB_SERVICE_H_