[Chrome OS Tether] Create BleAdvertisementDeviceQueue.

chromeos/components/tether/ble_advertisement_device_queue.h

Index: chromeos/components/tether/ble_advertisement_device_queue.h
diff --git a/chromeos/components/tether/ble_advertisement_device_queue.h b/chromeos/components/tether/ble_advertisement_device_queue.h
new file mode 100644
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+++ b/chromeos/components/tether/ble_advertisement_device_queue.h
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+// Copyright 2016 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 CHROMEOS_COMPONENTS_TETHER_BLE_ADVERTISEMENT_DEVICE_QUEUE_H_
+#define CHROMEOS_COMPONENTS_TETHER_BLE_ADVERTISEMENT_DEVICE_QUEUE_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "components/cryptauth/remote_device.h"
+
+namespace chromeos {
+
+namespace tether {
+
+// Queue of devices to which to advertise. Because only
+// |kMaxConcurrentAdvertisements| devices can be advertised to concurrently,
+// this queue maintains the order of devices to ensure that each device gets its
+// fair share of time spent contacting it.
+class BleAdvertisementDeviceQueue {
+ public:
+  // The maximum number of devices to which to advertise concurrently. If more
+  // than this number of devices are registered, some advertisement must be
+  // stopped before new ones can be added.
+  //
+  // Note that this upper limit on concurrent advertisements is imposed due to a
+  // hardware limit of advertisements.
+  static const int kMaxConcurrentAdvertisements;
+
+  BleAdvertisementDeviceQueue();
+  virtual ~BleAdvertisementDeviceQueue();
+
+  // Updates the queue with the given |devices|. Devices which are already in
+  // the queue and are not in |devices| are removed from the queue, and all
+  // devices which are not in the queue but are in |devices| are added to the
+  // end of the queue. Note devices that are already in the queue will not
+  // change order as a result of this function being called to ensure that the
+  // queue remains in order. Returns whether the device list has changed due to
+  // the function call.
+  bool SetDevices(std::vector<cryptauth::RemoteDevice> devices);
+
+  // Moves the given device to the end of the queue. If the device was not in
+  // the queue to begin with, do nothing.
+  void MoveDeviceToEnd(std::string device_id);
+
+  // Returns a list of devices to which to advertise. The devices returned are
+  // the first |kMaxConcurrentAdvertisements| devices in the front of the queue,
+  // or fewer if the number of devices in the queue is less than that value.
+  std::vector<cryptauth::RemoteDevice> GetDevicesToWhichToAdvertise() const;
+
+  size_t GetSize() const;
+
+ private:
+  std::vector<cryptauth::RemoteDevice> device_queue_;
+
+  DISALLOW_COPY_AND_ASSIGN(BleAdvertisementDeviceQueue);
+};
+
+}  // namespace tether
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_COMPONENTS_TETHER_BLE_ADVERTISEMENT_DEVICE_QUEUE_H_