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IncomingPacketHistoryCollection.cs 2.8 KB

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  1. /*
  2. * Copyright (c) Contributors, http://opensimulator.org/
  3. * See CONTRIBUTORS.TXT for a full list of copyright holders.
  4. *
  5. * Redistribution and use in source and binary forms, with or without
  6. * modification, are permitted provided that the following conditions are met:
  7. * * Redistributions of source code must retain the above copyright
  8. * notice, this list of conditions and the following disclaimer.
  9. * * Redistributions in binary form must reproduce the above copyright
  10. * notice, this list of conditions and the following disclaimer in the
  11. * documentation and/or other materials provided with the distribution.
  12. * * Neither the name of the OpenSimulator Project nor the
  13. * names of its contributors may be used to endorse or promote products
  14. * derived from this software without specific prior written permission.
  15. *
  16. * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
  17. * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  18. * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  19. * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
  20. * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  21. * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  22. * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  23. * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24. * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  25. * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26. */
  27. using System;
  28. using System.Collections.Generic;
  29. namespace OpenSim.Region.ClientStack.LindenUDP
  30. {
  31. /// <summary>
  32. /// A circular buffer and hashset for tracking incoming packet sequence
  33. /// numbers
  34. /// </summary>
  35. public sealed class IncomingPacketHistoryCollection
  36. {
  37. private readonly uint[] m_items;
  38. private HashSet<uint> m_hashSet;
  39. private int m_first;
  40. private int m_next;
  41. private int m_capacity;
  42. public IncomingPacketHistoryCollection(int capacity)
  43. {
  44. this.m_capacity = capacity;
  45. m_items = new uint[capacity];
  46. m_hashSet = new HashSet<uint>();
  47. }
  48. public bool TryEnqueue(uint ack)
  49. {
  50. lock (m_hashSet)
  51. {
  52. if (m_hashSet.Add(ack))
  53. {
  54. m_items[m_next] = ack;
  55. m_next = (m_next + 1) % m_capacity;
  56. if (m_next == m_first)
  57. {
  58. m_hashSet.Remove(m_items[m_first]);
  59. m_first = (m_first + 1) % m_capacity;
  60. }
  61. return true;
  62. }
  63. }
  64. return false;
  65. }
  66. }
  67. }