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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;
namespace OpenSim.Region.ScriptEngine.XMREngine
{
/**
* @brief Implements a queue of XMRInstance's.
* Do our own queue to avoid shitty little mallocs.
*
* Note: looping inst.m_NextInst and m_PrevInst back to itself
* when inst is removed from a queue is purely for debug.
*/
public class XMRInstQueue
{
private XMRInstance m_Head = null;
private XMRInstance m_Tail = null;
/**
* @brief Insert instance at head of queue (in front of all others)
* @param inst = instance to insert
*/
public void InsertHead(XMRInstance inst)
{
if ((inst.m_PrevInst != inst) || (inst.m_NextInst != inst)) {
throw new Exception("already in list");
}
inst.m_PrevInst = null;
if ((inst.m_NextInst = m_Head) == null) {
m_Tail = inst;
} else {
m_Head.m_PrevInst = inst;
}
m_Head = inst;
}
/**
* @brief Insert instance at tail of queue (behind all others)
* @param inst = instance to insert
*/
public void InsertTail(XMRInstance inst)
{
if ((inst.m_PrevInst != inst) || (inst.m_NextInst != inst)) {
throw new Exception("already in list");
}
inst.m_NextInst = null;
if ((inst.m_PrevInst = m_Tail) == null) {
m_Head = inst;
} else {
m_Tail.m_NextInst = inst;
}
m_Tail = inst;
}
/**
* @brief Insert instance before another element in queue
* @param inst = instance to insert
* @param after = element that is to come after one being inserted
*/
public void InsertBefore(XMRInstance inst, XMRInstance after)
{
if ((inst.m_PrevInst != inst) || (inst.m_NextInst != inst)) {
throw new Exception("already in list");
}
if (after == null) {
InsertTail(inst);
} else {
inst.m_NextInst = after;
inst.m_PrevInst = after.m_PrevInst;
if (inst.m_PrevInst == null) {
m_Head = inst;
} else {
inst.m_PrevInst.m_NextInst = inst;
}
after.m_PrevInst = inst;
}
}
/**
* @brief Peek to see if anything in queue
* @returns first XMRInstance in queue but doesn't remove it
* null if queue is empty
*/
public XMRInstance PeekHead()
{
return m_Head;
}
/**
* @brief Remove first element from queue, if any
* @returns null if queue is empty
* else returns first element in queue and removes it
*/
public XMRInstance RemoveHead()
{
XMRInstance inst = m_Head;
if (inst != null) {
if ((m_Head = inst.m_NextInst) == null) {
m_Tail = null;
} else {
m_Head.m_PrevInst = null;
}
inst.m_NextInst = inst;
inst.m_PrevInst = inst;
}
return inst;
}
/**
* @brief Remove last element from queue, if any
* @returns null if queue is empty
* else returns last element in queue and removes it
*/
public XMRInstance RemoveTail()
{
XMRInstance inst = m_Tail;
if (inst != null) {
if ((m_Tail = inst.m_PrevInst) == null) {
m_Head = null;
} else {
m_Tail.m_NextInst = null;
}
inst.m_NextInst = inst;
inst.m_PrevInst = inst;
}
return inst;
}
/**
* @brief Remove arbitrary element from queue, if any
* @param inst = element to remove (assumed to be in the queue)
* @returns with element removed
*/
public void Remove(XMRInstance inst)
{
XMRInstance next = inst.m_NextInst;
XMRInstance prev = inst.m_PrevInst;
if ((prev == inst) || (next == inst)) {
throw new Exception("not in a list");
}
if (next == null) {
if (m_Tail != inst) {
throw new Exception("not in this list");
}
m_Tail = prev;
} else {
next.m_PrevInst = prev;
}
if (prev == null) {
if (m_Head != inst) {
throw new Exception("not in this list");
}
m_Head = next;
} else {
prev.m_NextInst = next;
}
inst.m_NextInst = inst;
inst.m_PrevInst = inst;
}
}
}
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