224 lines
8.2 KiB
C#
224 lines
8.2 KiB
C#
/*
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* Copyright (c) Contributors, http://opensimulator.org/
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* See CONTRIBUTORS.TXT for a full list of copyright holders.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the OpenSimulator Project nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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using System;
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namespace OpenSim.Region.ClientStack.LindenUDP
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{
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/// <summary>
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/// A hierarchical token bucket for bandwidth throttling. See
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/// http://en.wikipedia.org/wiki/Token_bucket for more information
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/// </summary>
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public class TokenBucket
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{
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/// <summary>Parent bucket to this bucket, or null if this is a root
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/// bucket</summary>
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TokenBucket parent;
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/// <summary>Size of the bucket in bytes. If zero, the bucket has
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/// infinite capacity</summary>
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int maxBurst;
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/// <summary>Rate that the bucket fills, in bytes per millisecond. If
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/// zero, the bucket always remains full</summary>
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int tokensPerMS;
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/// <summary>Number of tokens currently in the bucket</summary>
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int content;
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/// <summary>Time of the last drip, in system ticks</summary>
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int lastDrip;
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#region Properties
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/// <summary>
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/// The parent bucket of this bucket, or null if this bucket has no
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/// parent. The parent bucket will limit the aggregate bandwidth of all
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/// of its children buckets
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/// </summary>
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public TokenBucket Parent
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{
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get { return parent; }
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}
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/// <summary>
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/// Maximum burst rate in bytes per second. This is the maximum number
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/// of tokens that can accumulate in the bucket at any one time
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/// </summary>
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public int MaxBurst
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{
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get { return maxBurst; }
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set { maxBurst = (value >= 0 ? value : 0); }
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}
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/// <summary>
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/// The speed limit of this bucket in bytes per second. This is the
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/// number of tokens that are added to the bucket per second
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/// </summary>
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/// <remarks>Tokens are added to the bucket any time
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/// <seealso cref="RemoveTokens"/> is called, at the granularity of
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/// the system tick interval (typically around 15-22ms)</remarks>
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public int DripRate
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{
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get { return tokensPerMS * 1000; }
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set
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{
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if (value == 0)
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tokensPerMS = 0;
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else
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{
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int bpms = (int)((float)value / 1000.0f);
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if (bpms <= 0)
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tokensPerMS = 1; // 1 byte/ms is the minimum granularity
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else
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tokensPerMS = bpms;
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}
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}
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}
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/// <summary>
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/// The speed limit of this bucket in bytes per millisecond
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/// </summary>
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public int DripPerMS
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{
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get { return tokensPerMS; }
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}
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/// <summary>
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/// The number of bytes that can be sent at this moment. This is the
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/// current number of tokens in the bucket
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/// <remarks>If this bucket has a parent bucket that does not have
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/// enough tokens for a request, <seealso cref="RemoveTokens"/> will
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/// return false regardless of the content of this bucket</remarks>
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/// </summary>
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public int Content
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{
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get { return content; }
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}
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#endregion Properties
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/// <summary>
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/// Default constructor
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/// </summary>
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/// <param name="parent">Parent bucket if this is a child bucket, or
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/// null if this is a root bucket</param>
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/// <param name="maxBurst">Maximum size of the bucket in bytes, or
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/// zero if this bucket has no maximum capacity</param>
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/// <param name="dripRate">Rate that the bucket fills, in bytes per
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/// second. If zero, the bucket always remains full</param>
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public TokenBucket(TokenBucket parent, int maxBurst, int dripRate)
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{
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this.parent = parent;
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MaxBurst = maxBurst;
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DripRate = dripRate;
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lastDrip = Environment.TickCount & Int32.MaxValue;
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}
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/// <summary>
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/// Remove a given number of tokens from the bucket
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/// </summary>
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/// <param name="amount">Number of tokens to remove from the bucket</param>
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/// <returns>True if the requested number of tokens were removed from
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/// the bucket, otherwise false</returns>
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public bool RemoveTokens(int amount)
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{
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bool dummy;
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return RemoveTokens(amount, out dummy);
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}
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/// <summary>
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/// Remove a given number of tokens from the bucket
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/// </summary>
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/// <param name="amount">Number of tokens to remove from the bucket</param>
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/// <param name="dripSucceeded">True if tokens were added to the bucket
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/// during this call, otherwise false</param>
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/// <returns>True if the requested number of tokens were removed from
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/// the bucket, otherwise false</returns>
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public bool RemoveTokens(int amount, out bool dripSucceeded)
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{
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if (maxBurst == 0)
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{
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dripSucceeded = true;
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return true;
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}
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dripSucceeded = Drip();
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if (content - amount >= 0)
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{
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if (parent != null && !parent.RemoveTokens(amount))
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return false;
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content -= amount;
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return true;
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}
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else
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{
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return false;
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}
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}
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/// <summary>
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/// Add tokens to the bucket over time. The number of tokens added each
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/// call depends on the length of time that has passed since the last
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/// call to Drip
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/// </summary>
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/// <returns>True if tokens were added to the bucket, otherwise false</returns>
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public bool Drip()
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{
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if (tokensPerMS == 0)
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{
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content = maxBurst;
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return true;
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}
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else
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{
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int now = Environment.TickCount & Int32.MaxValue;
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int deltaMS = now - lastDrip;
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if (deltaMS <= 0)
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{
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if (deltaMS < 0)
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lastDrip = now;
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return false;
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}
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int dripAmount = deltaMS * tokensPerMS;
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if (dripAmount < 0)
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Console.WriteLine("MAY DAY MAY DAY! Drip amount is " + dripAmount + ". This should not happen");
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content = Math.Min(content + dripAmount, maxBurst);
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lastDrip = now;
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if (content < 0)
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Console.WriteLine("MAY DAY MAY DAY! Content is " + content + ". This should not happen");
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return true;
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}
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}
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}
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}
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