Do not allow a script to attach a prim if its being sat upon.

This prevents a stack overflow where a get position on the avatar will refer to the attachment which will in turn refer back to the avatar.
This required recording of all sitting avatars on a prim which is done separately from recording the sit target avatar.
Recording HashSet is null if there are no sitting avatars in order to save memory.

3 files changed, 122 insertions, 8 deletions

diff --git a/OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs b/OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs
index 4e0e183..fc04761 100644
--- a/OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs
+++ b/OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs
@@ -3401,6 +3401,20 @@ namespace OpenSim.Region.Framework.Scenes
             return count;
         }
 
+        /// <summary>
+        /// Gets the number of sitting avatars.
+        /// </summary>
+        /// <remarks>This applies to all sitting avatars whether there is a sit target set or not.</remarks>
+        /// <returns></returns>
+        public int GetSittingAvatarsCount()
+        {
+             int count = 0;
+
+             Array.ForEach<SceneObjectPart>(m_parts.GetArray(), p => count += p.GetSittingAvatarsCount());
+
+             return count;
+        }
+
         public override string ToString()
         {
             return String.Format("{0} {1} ({2})", Name, UUID, AbsolutePosition);
diff --git a/OpenSim/Region/Framework/Scenes/SceneObjectPart.cs b/OpenSim/Region/Framework/Scenes/SceneObjectPart.cs
index 3d81358..6518b84 100644
--- a/OpenSim/Region/Framework/Scenes/SceneObjectPart.cs
+++ b/OpenSim/Region/Framework/Scenes/SceneObjectPart.cs
@@ -374,7 +374,6 @@ namespace OpenSim.Region.Framework.Scenes
         private uint _category;
         private Int32 _creationDate;
         private uint _parentID = 0;
-        private UUID m_sitTargetAvatar = UUID.Zero;
         private uint _baseMask = (uint)PermissionMask.All;
         private uint _ownerMask = (uint)PermissionMask.All;
         private uint _groupMask = (uint)PermissionMask.None;
@@ -1233,13 +1232,20 @@ namespace OpenSim.Region.Framework.Scenes
         }
 
         /// <summary>
-        /// ID of the avatar that is sat on us.  If there is no such avatar then is UUID.Zero
+        /// ID of the avatar that is sat on us if we have a sit target.  If there is no such avatar then is UUID.Zero
         /// </summary>
-        public UUID SitTargetAvatar
-        {
-            get { return m_sitTargetAvatar; }
-            set { m_sitTargetAvatar = value; }
-        }
+        public UUID SitTargetAvatar { get; set; }
+
+        /// <summary>
+        /// IDs of all avatars start on this object part.
+        /// </summary>
+        /// <remarks>
+        /// We need to track this so that we can stop sat upon prims from being attached.
+        /// </remarks>
+        /// <value>
+        /// null if there are no sitting avatars.  This is to save us create a hashset for every prim in a scene.
+        /// </value>
+        private HashSet<UUID> m_sittingAvatars;
 
         public virtual UUID RegionID
         {
@@ -4493,5 +4499,83 @@ namespace OpenSim.Region.Framework.Scenes
             Color color = Color;
             return new Color4(color.R, color.G, color.B, (byte)(0xFF - color.A));
         }
+
+        /// <summary>
+        /// Record an avatar sitting on this part.
+        /// </summary>
+        /// <remarks>This is called for all the sitting avatars whether there is a sit target set or not.</remarks>
+        /// <returns>
+        /// true if the avatar was not already recorded, false otherwise.
+        /// </returns>
+        /// <param name='avatarId'></param>
+        protected internal bool AddSittingAvatar(UUID avatarId)
+        {
+            HashSet<UUID> sittingAvatars = m_sittingAvatars;
+
+            if (sittingAvatars == null)
+                sittingAvatars = new HashSet<UUID>();
+
+            lock (sittingAvatars)
+            {
+                m_sittingAvatars = sittingAvatars;
+                return m_sittingAvatars.Add(avatarId);
+            }
+        }
+
+        /// <summary>
+        /// Remove an avatar recorded as sitting on this part.
+        /// </summary>
+        /// <remarks>This applies to all sitting avatars whether there is a sit target set or not.</remarks>
+        /// <returns>
+        /// true if the avatar was present and removed, false if it was not present.
+        /// </returns>
+        /// <param name='avatarId'></param>
+        protected internal bool RemoveSittingAvatar(UUID avatarId)
+        {
+            HashSet<UUID> sittingAvatars = m_sittingAvatars;
+
+            // This can occur under a race condition where another thread
+            if (sittingAvatars == null)
+                return false;
+
+            lock (sittingAvatars)
+            {
+                if (sittingAvatars.Remove(avatarId))
+                {
+                    if (sittingAvatars.Count == 0)
+                        m_sittingAvatars = null;
+
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Get a copy of the list of sitting avatars.
+        /// </summary>
+        /// <remarks>This applies to all sitting avatars whether there is a sit target set or not.</remarks>
+        /// <returns></returns>
+        public HashSet<UUID> GetSittingAvatars()
+        {
+            return new HashSet<UUID>(m_sittingAvatars);
+        }
+
+        /// <summary>
+        /// Gets the number of sitting avatars.
+        /// </summary>
+        /// <remarks>This applies to all sitting avatars whether there is a sit target set or not.</remarks>
+        /// <returns></returns>
+        public int GetSittingAvatarsCount()
+        {
+            HashSet<UUID> sittingAvatars = m_sittingAvatars;
+
+            if (sittingAvatars == null)
+                return 0;
+
+            lock (sittingAvatars)
+                return sittingAvatars.Count;
+        }
     }
 }
diff --git a/OpenSim/Region/Framework/Scenes/ScenePresence.cs b/OpenSim/Region/Framework/Scenes/ScenePresence.cs
index c7a670f..c6a2a03 100644
--- a/OpenSim/Region/Framework/Scenes/ScenePresence.cs
+++ b/OpenSim/Region/Framework/Scenes/ScenePresence.cs
@@ -578,6 +578,12 @@ namespace OpenSim.Region.Framework.Scenes
         public uint ParentID { get; set; }
 
         /// <summary>
+        /// Are we sitting on an object?
+        /// </summary>
+        /// <remarks>A more readable way of testing presence sit status than ParentID == 0</remarks>
+        public bool IsSatOnObject { get { return ParentID != 0; } }
+
+        /// <summary>
         /// If the avatar is sitting, the prim that it's sitting on.  If not sitting then null.
         /// </summary>
         /// <remarks>
@@ -1808,6 +1814,8 @@ namespace OpenSim.Region.Framework.Scenes
                 SendAvatarDataToAllAgents();
                 m_requestedSitTargetID = 0;
 
+                part.RemoveSittingAvatar(UUID);
+
                 if (part != null)
                     part.ParentGroup.TriggerScriptChangedEvent(Changed.LINK);
             }
@@ -1887,7 +1895,7 @@ namespace OpenSim.Region.Framework.Scenes
                    )
                    ));
 
-//                m_log.DebugFormat("[SCENE PRESENCE]: {0} {1}", SitTargetisSet, SitTargetUnOccupied);
+            m_log.DebugFormat("[SCENE PRESENCE]: {0} {1}", SitTargetisSet, SitTargetUnOccupied);
 
             if (PhysicsActor != null)
                 m_sitAvatarHeight = PhysicsActor.Size.Z;
@@ -1920,6 +1928,12 @@ namespace OpenSim.Region.Framework.Scenes
                     AbsolutePosition = pos + new Vector3(0.0f, 0.0f, m_sitAvatarHeight);
                     canSit = true;
                 }
+//                else
+//                {
+//                    m_log.DebugFormat(
+//                        "[SCENE PRESENCE]: Ignoring sit request of {0} on {1} {2} because sit target is unset and outside 10m",
+//                        Name, part.Name, part.LocalId);
+//                }
             }
 
             if (canSit)
@@ -1930,6 +1944,8 @@ namespace OpenSim.Region.Framework.Scenes
                     RemoveFromPhysicalScene();
                 }
 
+                part.AddSittingAvatar(UUID);
+
                 cameraAtOffset = part.GetCameraAtOffset();
                 cameraEyeOffset = part.GetCameraEyeOffset();
                 forceMouselook = part.GetForceMouselook();