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* Copyright (c) Contributors, http://opensimulator.org/
* See CONTRIBUTORS.TXT for a full list of copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the OpenSimulator Project nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
using System;
using System.Collections.Generic;
using System.Net;
using OpenMetaverse;
namespace OpenSim.Region.ClientStack.LindenUDP
{
/// <summary>
/// Special collection that is optimized for tracking unacknowledged packets
/// </summary>
public sealed class UnackedPacketCollection
{
/// <summary>
/// Holds information about a pending acknowledgement
/// </summary>
private struct PendingAck
{
/// <summary>Sequence number of the packet to remove</summary>
public uint SequenceNumber;
/// <summary>Environment.TickCount value when the remove was queued.
/// This is used to update round-trip times for packets</summary>
public int RemoveTime;
/// <summary>Whether or not this acknowledgement was attached to a
/// resent packet. If so, round-trip time will not be calculated</summary>
public bool FromResend;
public PendingAck(uint sequenceNumber, int currentTime, bool fromResend)
{
SequenceNumber = sequenceNumber;
RemoveTime = currentTime;
FromResend = fromResend;
}
}
/// <summary>Holds the actual unacked packet data, sorted by sequence number</summary>
private Dictionary<uint, OutgoingPacket> m_packets = new Dictionary<uint, OutgoingPacket>();
/// <summary>Holds packets that need to be added to the unacknowledged list</summary>
private LocklessQueue<OutgoingPacket> m_pendingAdds = new LocklessQueue<OutgoingPacket>();
/// <summary>Holds information about pending acknowledgements</summary>
private LocklessQueue<PendingAck> m_pendingRemoves = new LocklessQueue<PendingAck>();
/// <summary>
/// Add an unacked packet to the collection
/// </summary>
/// <param name="packet">Packet that is awaiting acknowledgement</param>
/// <returns>True if the packet was successfully added, false if the
/// packet already existed in the collection</returns>
/// <remarks>This does not immediately add the ACK to the collection,
/// it only queues it so it can be added in a thread-safe way later</remarks>
public void Add(OutgoingPacket packet)
{
m_pendingAdds.Enqueue(packet);
}
/// <summary>
/// Marks a packet as acknowledged
/// </summary>
/// <param name="sequenceNumber">Sequence number of the packet to
/// acknowledge</param>
/// <param name="currentTime">Current value of Environment.TickCount</param>
/// <remarks>This does not immediately acknowledge the packet, it only
/// queues the ack so it can be handled in a thread-safe way later</remarks>
public void Remove(uint sequenceNumber, int currentTime, bool fromResend)
{
m_pendingRemoves.Enqueue(new PendingAck(sequenceNumber, currentTime, fromResend));
}
/// <summary>
/// Returns a list of all of the packets with a TickCount older than
/// the specified timeout
/// </summary>
/// <param name="timeoutMS">Number of ticks (milliseconds) before a
/// packet is considered expired</param>
/// <returns>A list of all expired packets according to the given
/// expiration timeout</returns>
/// <remarks>This function is not thread safe, and cannot be called
/// multiple times concurrently</remarks>
public List<OutgoingPacket> GetExpiredPackets(int timeoutMS)
{
ProcessQueues();
List<OutgoingPacket> expiredPackets = null;
if (m_packets.Count > 0)
{
int now = Environment.TickCount & Int32.MaxValue;
foreach (OutgoingPacket packet in m_packets.Values)
{
// TickCount of zero means a packet is in the resend queue
// but hasn't actually been sent over the wire yet
if (packet.TickCount == 0)
continue;
if (now - packet.TickCount >= timeoutMS)
{
if (expiredPackets == null)
expiredPackets = new List<OutgoingPacket>();
// The TickCount will be set to the current time when the packet
// is actually sent out again
packet.TickCount = 0;
expiredPackets.Add(packet);
}
}
}
return expiredPackets;
}
private void ProcessQueues()
{
// Process all the pending adds
OutgoingPacket pendingAdd;
if (m_pendingAdds != null)
{
while (m_pendingAdds.TryDequeue(out pendingAdd))
{
if (pendingAdd != null && m_packets != null)
{
m_packets[pendingAdd.SequenceNumber] = pendingAdd;
}
}
}
// Process all the pending removes, including updating statistics and round-trip times
PendingAck pendingRemove;
OutgoingPacket ackedPacket;
if (m_pendingRemoves != null)
{
while (m_pendingRemoves.TryDequeue(out pendingRemove))
{
if (m_pendingRemoves != null && m_packets != null)
{
if (m_packets.TryGetValue(pendingRemove.SequenceNumber, out ackedPacket))
{
m_packets.Remove(pendingRemove.SequenceNumber);
// Update stats
System.Threading.Interlocked.Add(ref ackedPacket.Client.UnackedBytes, -ackedPacket.Buffer.DataLength);
if (!pendingRemove.FromResend)
{
// Calculate the round-trip time for this packet and its ACK
int rtt = pendingRemove.RemoveTime - ackedPacket.TickCount;
if (rtt > 0)
ackedPacket.Client.UpdateRoundTrip(rtt);
}
}
}
}
}
}
}
}
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