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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.Framework.Scenes
{
/// <summary>
/// The possible states that a scene presence can be in. This is currently orthagonal to whether a scene presence
/// is root or child.
/// </summary>
/// <remarks>
/// This is a state machine.
///
/// [Entry] => Running
/// Running => PreRemove, Removing
/// PreRemove => Running, Removing
/// Removing => Removed
///
/// All other methods should only see the scene presence in running state - this is the normal operational state
/// Removed state occurs when the presence has been removed. This is the end state with no exit.
/// </remarks>
public enum ScenePresenceState
{
Running, // Normal operation state. The scene presence is available.
PreRemove, // The presence is due to be removed but can still be returning to running.
Removing, // The presence is in the process of being removed from the scene via Scene.RemoveClient.
Removed, // The presence has been removed from the scene and is effectively dead.
// There is no exit from this state.
}
internal class ScenePresenceStateMachine
{
private ScenePresence m_sp;
private ScenePresenceState m_state;
internal ScenePresenceStateMachine(ScenePresence sp)
{
m_sp = sp;
m_state = ScenePresenceState.Running;
}
internal ScenePresenceState GetState()
{
return m_state;
}
/// <summary>
/// Updates the state of an agent that is already in transit.
/// </summary>
/// <param name='id'></param>
/// <param name='newState'></param>
/// <returns></returns>
/// <exception cref='Exception'>Illegal transitions will throw an Exception</exception>
internal void SetState(ScenePresenceState newState)
{
bool transitionOkay = false;
lock (this)
{
if (newState == m_state)
return;
else if (newState == ScenePresenceState.Running && m_state == ScenePresenceState.PreRemove)
transitionOkay = true;
else if (newState == ScenePresenceState.PreRemove && m_state == ScenePresenceState.Running)
transitionOkay = true;
else if (newState == ScenePresenceState.Removing)
{
if (m_state == ScenePresenceState.Running || m_state == ScenePresenceState.PreRemove)
transitionOkay = true;
}
else if (newState == ScenePresenceState.Removed && m_state == ScenePresenceState.Removing)
transitionOkay = true;
}
if (!transitionOkay)
{
throw new Exception(
string.Format(
"Scene presence {0} is not allowed to move from state {1} to new state {2} in {3}",
m_sp.Name, m_state, newState, m_sp.Scene.Name));
}
else
{
m_state = newState;
}
}
}
}
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