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1//
2// Lazy.cs
3//
4// Authors:
5// Zoltan Varga (vargaz@gmail.com)
6// Marek Safar (marek.safar@gmail.com)
7//
8// Copyright (C) 2009 Novell
9//
10// Permission is hereby granted, free of charge, to any person obtaining
11// a copy of this software and associated documentation files (the
12// "Software"), to deal in the Software without restriction, including
13// without limitation the rights to use, copy, modify, merge, publish,
14// distribute, sublicense, and/or sell copies of the Software, and to
15// permit persons to whom the Software is furnished to do so, subject to
16// the following conditions:
17//
18// The above copyright notice and this permission notice shall be
19// included in all copies or substantial portions of the Software.
20//
21// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
22// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
23// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
24// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
25// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
26// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
27// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
28//
29
30using System;
31using System.Runtime.Serialization;
32using System.Runtime.InteropServices;
33using System.Security.Permissions;
34using System.Threading;
35using System.Diagnostics;
36
37namespace OpenSim.Framework
38{
39 public enum LazyThreadSafetyMode
40 {
41 None,
42 PublicationOnly,
43 ExecutionAndPublication
44 }
45
46 [SerializableAttribute]
47 [ComVisibleAttribute(false)]
48 [HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, ExternalThreading = true)]
49 public class Lazy<T>
50 {
51 T value;
52 bool inited;
53 LazyThreadSafetyMode mode;
54 Func<T> factory;
55 object monitor;
56 Exception exception;
57
58 public Lazy()
59 : this(LazyThreadSafetyMode.ExecutionAndPublication)
60 {
61 }
62
63 public Lazy(Func<T> valueFactory)
64 : this(valueFactory, LazyThreadSafetyMode.ExecutionAndPublication)
65 {
66 }
67
68 public Lazy(bool isThreadSafe)
69 : this(() => Activator.CreateInstance<T>(), isThreadSafe ? LazyThreadSafetyMode.ExecutionAndPublication : LazyThreadSafetyMode.None)
70 {
71 }
72
73 public Lazy(Func<T> valueFactory, bool isThreadSafe)
74 : this(valueFactory, isThreadSafe ? LazyThreadSafetyMode.ExecutionAndPublication : LazyThreadSafetyMode.None)
75 {
76 }
77
78 public Lazy(LazyThreadSafetyMode mode)
79 : this(() => Activator.CreateInstance<T>(), mode)
80 {
81 }
82
83 public Lazy(Func<T> valueFactory, LazyThreadSafetyMode mode)
84 {
85 if (valueFactory == null)
86 throw new ArgumentNullException("valueFactory");
87 this.factory = valueFactory;
88 if (mode != LazyThreadSafetyMode.None)
89 monitor = new object();
90 this.mode = mode;
91 }
92
93 // Don't trigger expensive initialization
94 [DebuggerBrowsable(DebuggerBrowsableState.Never)]
95 public T Value
96 {
97 get
98 {
99 if (inited)
100 return value;
101 if (exception != null)
102 throw exception;
103
104 return InitValue();
105 }
106 }
107
108 T InitValue()
109 {
110 switch (mode)
111 {
112 case LazyThreadSafetyMode.None:
113 {
114 var init_factory = factory;
115 if (init_factory == null)
116 throw exception = new InvalidOperationException("The initialization function tries to access Value on this instance");
117 try
118 {
119 factory = null;
120 T v = init_factory();
121 value = v;
122 Thread.MemoryBarrier();
123 inited = true;
124 }
125 catch (Exception ex)
126 {
127 exception = ex;
128 throw;
129 }
130 break;
131 }
132 case LazyThreadSafetyMode.PublicationOnly:
133 {
134 var init_factory = factory;
135 T v;
136
137 //exceptions are ignored
138 if (init_factory != null)
139 v = init_factory();
140 else
141 v = default(T);
142
143 lock (monitor)
144 {
145 if (inited)
146 return value;
147 value = v;
148 Thread.MemoryBarrier();
149 inited = true;
150 factory = null;
151 }
152 break;
153 }
154 case LazyThreadSafetyMode.ExecutionAndPublication:
155 {
156 lock (monitor)
157 {
158 if (inited)
159 return value;
160
161 if (factory == null)
162 throw exception = new InvalidOperationException("The initialization function tries to access Value on this instance");
163
164 var init_factory = factory;
165 try
166 {
167 factory = null;
168 T v = init_factory();
169 value = v;
170 Thread.MemoryBarrier();
171 inited = true;
172 }
173 catch (Exception ex)
174 {
175 exception = ex;
176 throw;
177 }
178 }
179 break;
180 }
181 default:
182 throw new InvalidOperationException("Invalid LazyThreadSafetyMode " + mode);
183 }
184
185 if (monitor == null)
186 {
187 value = factory();
188 inited = true;
189 }
190 else
191 {
192 lock (monitor)
193 {
194 if (inited)
195 return value;
196
197 if (factory == null)
198 throw new InvalidOperationException("The initialization function tries to access Value on this instance");
199
200 var init_factory = factory;
201 try
202 {
203 factory = null;
204 T v = init_factory();
205 value = v;
206 Thread.MemoryBarrier();
207 inited = true;
208 }
209 catch
210 {
211 factory = init_factory;
212 throw;
213 }
214 }
215 }
216
217 return value;
218 }
219
220 public bool IsValueCreated
221 {
222 get
223 {
224 return inited;
225 }
226 }
227
228 public override string ToString()
229 {
230 if (inited)
231 return value.ToString();
232 else
233 return "Value is not created";
234 }
235 }
236}