source: cpp/frams/util/usertags.h @ 109

Last change on this file since 109 was 109, checked in by sz, 9 years ago

source reorganization (see README)
new feature added: part/joint shapes (see frams/_demos/part_shapes.cpp)

  • Property svn:eol-style set to native
File size: 2.3 KB
1// This file is a part of the Framsticks GDK library.
2// Copyright (C) 2002-2011  Szymon Ulatowski.  See LICENSE.txt for details.
3// Refer to for further information.
5#ifndef _USERTAGS_H_
6#define _USERTAGS_H_
9  UserTags is the fast way to associate custom data with general purpose objects.
10  Objects don't have to know about their users and we can add more users later without recompilation.
11  For example: MechObject is general physical object in MechaStick engine.
12  In Framsticks simulator every MechObject is connected with Model object, MechParts and MechJoints are
13  connected with their counterparts in the Model as well, but the MechObject doesn't even know about it.
14  If the SSG visualisation is used, the same MechObject is also connected with SSGFramObject.
15  UserTags class is implemented as array, therefore the access is very fast but we have to define
16  maximum possible number of tags for every object:
18  UserTags<anyclass,datatype,maximumtags> object;
19  (all UserTags object for a given 'anyclass' will share registered id's)
21  usage:
22    1.allocate private id:
23       int id=object->userdata.newID();
24    'id' is shared across all objects of that class (in this example)
25    and therefore you need to allocate it only once.
26    0 is illegal here and means that we run out of id values.
28 you can use id to access your private data inside UserTags:
29       object->userdata[id]=...;
30       ...=object->userdata[id];
31       ...
32 can also assign/access object->userdata (which is a shortcut for
33    object->userdata[0]). no id here, so in that case it is your responsibility
34    to avoid conflicts.
35       object->userdata=...;
36       ...=object->userdata;
37       ...
39 your id when finished:
40       object->userdata.freeID(id);
41 */
43template<class ID,class T,int N> class UserTags
45static char reg[N];
46T data[N];
47  public:
48UserTags() {memset(data,0,sizeof(data));}
50/** allocate new id */
51static int newID()
52        { for(int i=1;i<N;i++) if (!reg[i]) {reg[i]=1; return i;}
53        DB(printf("Warning: UserTags run out of ids!\n"));
54          return 0; }
55static void freeID(int id)
56        { reg[id]=0; }
57T& operator[](int id)
58        {
59        DB(if (!id) printf("Warning: UserTags @ %p is using id=0\n",this);)
60        return data[id];
61        }
62operator T() { return data[0]; }
63void operator=(T x) { data[0]=x; }
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