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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.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 speed limit of this bucket in bytes per millisecond
/// </summary>
public int 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"/> 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;
}
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>
public 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;
}
}
}
}
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