/Aurora/ClientStack/TokenBucket.cs
https://bitbucket.org/VirtualReality/software-testing · C# · 250 lines · 94 code · 24 blank · 132 comment · 11 complexity · 47af40ebdb290becee39ebc6a8e6b543 MD5 · raw file
- /*
- * Copyright (c) Contributors, http://aurora-sim.org/, 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 Aurora-Sim 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 Aurora.ClientStack
- {
- /// <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>
- private readonly TokenBucket parent;
-
- /// <summary>
- /// Number of tokens currently in the bucket
- /// </summary>
- private int content;
-
- /// <summary>
- /// Time of the last drip, in system ticks
- /// </summary>
- private int lastDrip;
-
- /// <summary>
- /// Size of the bucket in bytes. If zero, the bucket has
- /// infinite capacity
- /// </summary>
- private int maxBurst;
-
- /// <summary>
- /// Rate that the bucket fills, in bytes per millisecond. If
- /// zero, the bucket always remains full
- /// </summary>
- private float tokensPerMS;
-
- #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</cref>
- /// </seealso>
- /// is called, at the granularity of
- /// the system tick interval (typically around 15-22ms)
- /// </remarks>
- public float DripRate
- {
- get { return tokensPerMS*1000; }
- set
- {
- if (value == 0)
- tokensPerMS = 0;
- else
- {
- float bpms = (int) (value/1000.0f);
-
- tokensPerMS = bpms <= 0.5f ? .5f : bpms;
- }
- }
- }
-
- /// <summary>
- /// The speed limit of this bucket in bytes per millisecond
- /// </summary>
- public float DripPerMS
- {
- get { return tokensPerMS; }
- }
-
- /// <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</cref>
- /// </seealso>
- /// will
- /// return false regardless of the content of this bucket
- /// </remarks>
- /// </summary>
- public int Content
- {
- get { 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;
- }
- 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>
- public bool Drip()
- {
- if (tokensPerMS <= 0)
- {
- content = maxBurst;
- return true;
- }
- int now = Environment.TickCount & Int32.MaxValue;
- int deltaMS = now - lastDrip;
-
- if (deltaMS <= 0)
- {
- if (deltaMS < 0)
- lastDrip = now;
- return false;
- }
-
- int dripAmount = (int) (deltaMS*tokensPerMS);
-
- content = Math.Min(content + dripAmount, maxBurst);
- lastDrip = now;
- /*
- if (dripAmount < 0 || content < 0)
- // sim has been idle for too long, integer has overflown
- // previous calculation is meaningless, let's put it at correct max
- content = maxBurst;
- */
- return true;
- }
- }
- }