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
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!--Converted with LaTeX2HTML 2002-2-1 (1.71)
original version by: Nikos Drakos, CBLU, University of Leeds
* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
* with significant contributions from:
Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
<HTML>
<HEAD>
<TITLE>2 Object system implementation</TITLE>
<META NAME="description" CONTENT="2 Object system implementation">
<META NAME="keywords" CONTENT="ionnotes">
<META NAME="resource-type" CONTENT="document">
<META NAME="distribution" CONTENT="global">
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Generator" CONTENT="LaTeX2HTML v2002-2-1">
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">
<LINK REL="STYLESHEET" HREF="ionnotes.css">
<LINK REL="next" HREF="node4.html">
<LINK REL="previous" HREF="node2.html">
<LINK REL="up" HREF="ionnotes.html">
<LINK REL="next" HREF="node4.html">
</HEAD>
<BODY >
<DIV CLASS="navigation"><!--Navigation Panel-->
<A NAME="tex2html100"
HREF="node4.html">
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A>
<A NAME="tex2html94"
HREF="ionnotes.html">
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A>
<A NAME="tex2html88"
HREF="node2.html">
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A>
<A NAME="tex2html96"
HREF="node1.html">
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A>
<A NAME="tex2html98"
HREF="node8.html">
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index.png"></A>
<BR>
<B> Next:</B> <A NAME="tex2html101"
HREF="node4.html">3 The Lua interface</A>
<B> Up:</B> <A NAME="tex2html95"
HREF="ionnotes.html">Ion: Notes for the</A>
<B> Previous:</B> <A NAME="tex2html89"
HREF="node2.html">1 Class and object</A>
<B> <A NAME="tex2html97"
HREF="node1.html">Contents</A></B>
<B> <A NAME="tex2html99"
HREF="node8.html">Index</A></B>
<BR>
<BR></DIV>
<!--End of Navigation Panel-->
<H1><A NAME="SECTION00030000000000000000">
<SPAN CLASS="arabic">2</SPAN> Object system implementation</A>
</H1>
<P>
First, to get things clear, what are considered objects here are C
structures containing a properly initialised <A NAME="432"></A>
structure defined in <SPAN CLASS="textit">ioncore/obj.h</SPAN> as the first element (or the
first element of the structure which is the first element and so on which
gives rise to inheritance). The WObj structure contains a pointer
to a WObjDescr<A NAME="434"></A> class type info structure and
a list of so called ``watches''. The WObjDescr structure simply
lists the class name, a table of dynamic functions and a pointer to
deinitialisation function (or ``destructor'').
<P>
Ion does not do any reference counting, garbage collecting or other
fancy things related to automatic safe freeing of objects with its
simplistic object system. Instead special watches (the WWatch
<A NAME="435"></A> structure) may be used to create safe references to
objects that might be destroyed during the time the specific pointer is
needed. When an object is destroyed, its list of watches is processed,
setting the pointers in the watches to NULL and the watch handlers for
each watch are called.
<P>
<P>
<DIV CLASS="navigation"><HR>
<!--Navigation Panel-->
<A NAME="tex2html100"
HREF="node4.html">
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A>
<A NAME="tex2html94"
HREF="ionnotes.html">
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A>
<A NAME="tex2html88"
HREF="node2.html">
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A>
<A NAME="tex2html96"
HREF="node1.html">
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A>
<A NAME="tex2html98"
HREF="node8.html">
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index.png"></A>
<BR>
<B> Next:</B> <A NAME="tex2html101"
HREF="node4.html">3 The Lua interface</A>
<B> Up:</B> <A NAME="tex2html95"
HREF="ionnotes.html">Ion: Notes for the</A>
<B> Previous:</B> <A NAME="tex2html89"
HREF="node2.html">1 Class and object</A>
<B> <A NAME="tex2html97"
HREF="node1.html">Contents</A></B>
<B> <A NAME="tex2html99"
HREF="node8.html">Index</A></B> </DIV>
<!--End of Navigation Panel-->
</BODY>
</HTML>
|
