1 files changed, 213 insertions, 0 deletions

diff --git a/OpenSim/Region/ClientStack/LindenUDP/TokenBucket.cs b/OpenSim/Region/ClientStack/LindenUDP/TokenBucket.cs
new file mode 100644
index 0000000..0a64095
--- /dev/null
+++ b/OpenSim/Region/ClientStack/LindenUDP/TokenBucket.cs
@@ -0,0 +1,213 @@
+/*
+ * 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.ClientStack.LindenUDP
+{
+    /// <summary>
+    /// A hierarchical token bucket for bandwidth throttling. See
+    /// http://en.wikipedia.org/wiki/Token_bucket for more information
+    /// </summary>
+    public class TokenBucket
+    {
+        /// <summary>Parent bucket to this bucket, or null if this is a root
+        /// bucket</summary>
+        TokenBucket parent;
+        /// <summary>Size of the bucket in bytes. If zero, the bucket has 
+        /// infinite capacity</summary>
+        int maxBurst;
+        /// <summary>Rate that the bucket fills, in bytes per millisecond. If
+        /// zero, the bucket always remains full</summary>
+        int tokensPerMS;
+        /// <summary>Number of tokens currently in the bucket</summary>
+        int content;
+        /// <summary>Time of the last drip, in system ticks</summary>
+        int lastDrip;
+
+        #region Properties
+
+        /// <summary>
+        /// The parent bucket of this bucket, or null if this bucket has no
+        /// parent. The parent bucket will limit the aggregate bandwidth of all
+        /// of its children buckets
+        /// </summary>
+        public TokenBucket Parent
+        {
+            get { return parent; }
+        }
+
+        /// <summary>
+        /// Maximum burst rate in bytes per second. This is the maximum number
+        /// of tokens that can accumulate in the bucket at any one time
+        /// </summary>
+        public int MaxBurst
+        {
+            get { return maxBurst; }
+            set { maxBurst = (value >= 0 ? value : 0); }
+        }
+
+        /// <summary>
+        /// The speed limit of this bucket in bytes per second. This is the
+        /// number of tokens that are added to the bucket per second
+        /// </summary>
+        /// <remarks>Tokens are added to the bucket any time 
+        /// <seealso cref="RemoveTokens"/> is called, at the granularity of
+        /// the system tick interval (typically around 15-22ms)</remarks>
+        public int DripRate
+        {
+            get { return tokensPerMS * 1000; }
+            set
+            {
+                if (value == 0)
+                    tokensPerMS = 0;
+                else
+                {
+                    int bpms = (int)((float)value / 1000.0f);
+
+                    if (bpms <= 0)
+                        tokensPerMS = 1; // 1 byte/ms is the minimum granularity
+                    else
+                        tokensPerMS = bpms;
+                }
+            }
+        }
+
+        /// <summary>
+        /// The number of bytes that can be sent at this moment. This is the
+        /// current number of tokens in the bucket
+        /// <remarks>If this bucket has a parent bucket that does not have
+        /// enough tokens for a request, <seealso cref="RemoveTokens"/> will 
+        /// return false regardless of the content of this bucket</remarks>
+        /// </summary>
+        public int Content
+        {
+            get
+            {
+                Drip();
+                return content;
+            }
+        }
+
+        #endregion Properties
+
+        /// <summary>
+        /// Default constructor
+        /// </summary>
+        /// <param name="parent">Parent bucket if this is a child bucket, or
+        /// null if this is a root bucket</param>
+        /// <param name="maxBurst">Maximum size of the bucket in bytes, or
+        /// zero if this bucket has no maximum capacity</param>
+        /// <param name="dripRate">Rate that the bucket fills, in bytes per
+        /// second. If zero, the bucket always remains full</param>
+        public TokenBucket(TokenBucket parent, int maxBurst, int dripRate)
+        {
+            this.parent = parent;
+            MaxBurst = maxBurst;
+            DripRate = dripRate;
+            lastDrip = Environment.TickCount & Int32.MaxValue;
+        }
+
+        /// <summary>
+        /// Remove a given number of tokens from the bucket
+        /// </summary>
+        /// <param name="amount">Number of tokens to remove from the bucket</param>
+        /// <returns>True if the requested number of tokens were removed from
+        /// the bucket, otherwise false</returns>
+        public bool RemoveTokens(int amount)
+        {
+            bool dummy;
+            return RemoveTokens(amount, out dummy);
+        }
+
+        /// <summary>
+        /// Remove a given number of tokens from the bucket
+        /// </summary>
+        /// <param name="amount">Number of tokens to remove from the bucket</param>
+        /// <param name="dripSucceeded">True if tokens were added to the bucket
+        /// during this call, otherwise false</param>
+        /// <returns>True if the requested number of tokens were removed from
+        /// the bucket, otherwise false</returns>
+        public bool RemoveTokens(int amount, out bool dripSucceeded)
+        {
+            if (maxBurst == 0)
+            {
+                dripSucceeded = true;
+                return true;
+            }
+
+            dripSucceeded = Drip();
+
+            if (content - amount >= 0)
+            {
+                if (parent != null && !parent.RemoveTokens(amount))
+                    return false;
+
+                content -= amount;
+                return true;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Add tokens to the bucket over time. The number of tokens added each
+        /// call depends on the length of time that has passed since the last 
+        /// call to Drip
+        /// </summary>
+        /// <returns>True if tokens were added to the bucket, otherwise false</returns>
+        private bool Drip()
+        {
+            if (tokensPerMS == 0)
+            {
+                content = maxBurst;
+                return true;
+            }
+            else
+            {
+                int now = Environment.TickCount & Int32.MaxValue;
+                int deltaMS = now - lastDrip;
+
+                if (deltaMS <= 0)
+                {
+                    if (deltaMS < 0)
+                        lastDrip = now;
+                    return false;
+                }
+
+                int dripAmount = deltaMS * tokensPerMS;
+
+                content = Math.Min(content + dripAmount, maxBurst);
+                lastDrip = now;
+
+                return true;
+            }
+        }
+    }
+}