opensim/OpenSim/Framework/PacketPool.cs

/*
* 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 OpenSim 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;
using libsecondlife.Packets;

namespace OpenSim.Framework
{
    public sealed class PacketPool
    {
        // Set up a thread-safe singleton pattern
        static PacketPool()
        {
        }

        private static readonly PacketPool instance = new PacketPool();

        public static PacketPool Instance
        {
            get { return instance; }
        }

        private Hashtable pool = new Hashtable();

        public Packet GetPacket(PacketType type)
        {
            return Packet.BuildPacket(type);
/* Skip until PacketPool performance problems have been resolved (mantis 281)
            Packet packet = null;

            lock (pool)
            {
                if (pool[type] == null || ((Stack) pool[type]).Count == 0)
                {
                    // Creating a new packet if we cannot reuse an old package
                    packet = Packet.BuildPacket(type);
                }
                else
                {
                    // Recycle old packages
                    packet = (Packet) ((Stack) pool[type]).Pop();
                }
            }

            return packet;
*/
        }

        // Copied from LibSL, and added a check to avoid overwriting the
        // buffer
        private void ZeroDecodeCommand(byte[] src, byte[] dest)
        {
            for (int srcPos = 6, destPos = 6; destPos < 10; ++srcPos)
            {
                if (src[srcPos] == 0x00)
                {
                    for (byte j = 0; j < src[srcPos + 1] && destPos < 10; ++j)
                    {
                        dest[destPos++] = 0x00;
                    }
                    ++srcPos;
                                                                                                }
                else
                {
                    dest[destPos++] = src[srcPos];
                }
            }
        }

        private PacketType GetType(byte[] bytes)
        {
            byte[] decoded_header = new byte[10];

            ushort id;
            libsecondlife.PacketFrequency freq;

            Buffer.BlockCopy(bytes, 0, decoded_header, 0, 10);

            if((bytes[0] & libsecondlife.Helpers.MSG_ZEROCODED)!=0)
            {
                ZeroDecodeCommand(bytes, decoded_header);
            }

            if (decoded_header[6] == 0xFF)
            {
                if (decoded_header[7] == 0xFF)
                {
                    id = (ushort)((decoded_header[8] << 8) + decoded_header[9]);
                    freq = libsecondlife.PacketFrequency.Low;
                }
                else
                {
                    id = (ushort)decoded_header[7];
                    freq = libsecondlife.PacketFrequency.Medium;
                }
            }
            else
            {
                id = (ushort)decoded_header[6];
                freq = libsecondlife.PacketFrequency.High;
            }
 
            return Packet.GetType(id, freq);
        }

        public Packet GetPacket(byte[] bytes, ref int packetEnd, byte[] zeroBuffer)
        {
            PacketType type = GetType(bytes);

            int i = 0;
            Packet packet = GetPacket(type);
            packet.FromBytes(bytes, ref i, ref packetEnd, zeroBuffer);
            return packet;
        }

        public void ReturnPacket(Packet packet) 
        {
/* Skip until PacketPool performance problems have been resolved (mantis 281)
            lock (pool)
            {
                PacketType type = packet.Type;

                if (pool[type] == null)
                {
                    pool[type] = new Stack();
                }

                ((Stack) pool[type]).Push(packet);
            }
*/
        }
    }
}