1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
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;
}
}
}
}
|
