2010-04-07 Jb Evain <jbevain@novell.com>
[mcs.git] / class / corlib / System.Runtime.Serialization / ObjectIDGenerator.cs
blob6e4f00ccfb3ef81f596e7f361ca63c86e1aff0f0
1 //
2 // System.Runtime.Serialization.ObjectIDGenerator.cs
3 //
4 // Author: Duncan Mak (duncan@ximian.com)
5 // Lluis Sanchez (lsg@ctv.es)
6 //
7 // (C) Ximian, Inc.
8 // Copyright (C) 2004,2006 Novell, Inc (http://www.novell.com)
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.
30 using System.Collections;
32 namespace System.Runtime.Serialization
34 [Serializable]
35 [MonoTODO ("Serialization format not compatible with.NET")]
36 [System.Runtime.InteropServices.ComVisibleAttribute (true)]
37 public class ObjectIDGenerator
39 // Private field
40 Hashtable table;
41 long current; // this is the current ID, starts at 1
42 static InstanceComparer comparer = new InstanceComparer ();
45 // ObjectIDGenerator must generate a new id for each object instance.
46 // If two objects have the same state (i.e. the method Equals() returns true),
47 // each one should have a different id.
48 // Thus, the object instance cannot be directly used as key of the hashtable.
49 // InstanceComparer compares object references instead of object content
50 // (unless the object is inmutable, like strings).
52 class InstanceComparer: IComparer, IHashCodeProvider
54 int IComparer.Compare (object o1, object o2)
56 if (o1 is string)
57 return o1.Equals(o2) ? 0 : 1;
58 else
59 return (o1 == o2) ? 0 : 1;
62 int IHashCodeProvider.GetHashCode (object o)
64 return object.InternalGetHashCode (o);
68 // constructor
69 public ObjectIDGenerator ()
70 : base ()
72 table = new Hashtable (comparer, comparer);
73 current = 1;
76 // Methods
77 public virtual long GetId (object obj, out bool firstTime)
79 if (obj == null)
80 throw new ArgumentNullException ("obj");
82 object val = table [obj];
84 if (val != null) {
85 firstTime = false;
86 return (long) val;
88 } else {
89 firstTime = true;
90 table.Add (obj, current);
91 return current ++;
95 public virtual long HasId (object obj, out bool firstTime)
97 if (obj == null)
98 throw new ArgumentNullException ("obj");
100 object val = table [obj];
102 if (val != null) {
103 firstTime = false;
104 return (long) val;
106 } else {
107 firstTime = true;
108 return 0L; // 0 is the null ID
112 internal long NextId
114 get { return current ++; }