1 /* src/vm/linker.h - class linker header
3 Copyright (C) 1996-2005 R. Grafl, A. Krall, C. Kruegel, C. Oates,
4 R. Obermaisser, M. Platter, M. Probst, S. Ring, E. Steiner,
5 C. Thalinger, D. Thuernbeck, P. Tomsich, C. Ullrich, J. Wenninger,
6 Institut f. Computersprachen - TU Wien
8 This file is part of CACAO.
10 This program is free software; you can redistribute it and/or
11 modify it under the terms of the GNU General Public License as
12 published by the Free Software Foundation; either version 2, or (at
13 your option) any later version.
15 This program is distributed in the hope that it will be useful, but
16 WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 General Public License for more details.
20 You should have received a copy of the GNU General Public License
21 along with this program; if not, write to the Free Software
22 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
25 Contact: cacao@complang.tuwien.ac.at
27 Authors: Christian Thalinger
31 $Id: linker.h 2101 2005-03-28 21:59:45Z twisti $
38 /* forward typedefs ***********************************************************/
40 typedef struct _vftbl vftbl_t;
46 /* virtual function table ******************************************************
48 The vtbl has a bidirectional layout with open ends at both sides.
49 interfacetablelength gives the number of entries of the interface
50 table at the start of the vftbl. The vftbl pointer points to
51 &interfacetable[0]. vftbllength gives the number of entries of
52 table at the end of the vftbl.
54 runtime type check (checkcast):
56 Different methods are used for runtime type check depending on the
57 argument of checkcast/instanceof.
59 A check against a class is implemented via relative numbering on
60 the class hierachy tree. The tree is numbered in a depth first
61 traversal setting the base field and the diff field. The diff field
62 gets the result of (high - base) so that a range check can be
63 implemented by an unsigned compare. A sub type test is done by
64 checking the inclusion of base of the sub class in the range of the
67 A check against an interface is implemented via the
68 interfacevftbl. If the interfacevftbl contains a nonnull value a
69 class is a subclass of this interface.
73 Like standard virtual methods interface methods are called using
74 virtual function tables. All interfaces are numbered sequentially
75 (starting with zero). For each class there exist an interface table
76 of virtual function tables for each implemented interface. The
77 length of the interface table is determined by the highest number
78 of an implemented interface.
80 The following example assumes a class which implements interface 0 and 3:
82 interfacetablelength = 4
85 +-----------+ | method 2 |---> method z
86 | class | | method 1 |---> method y
87 +-----------+ | method 0 |---> method x
88 | ivftbl 0 |----------> +----------+
89 vftblptr ---> +-----------+
90 | ivftbl -1 |--> NULL +----------+
91 | ivftbl -2 |--> NULL | method 1 |---> method x
92 | ivftbl -3 |-----+ | method 0 |---> method a
93 +-----------+ +----> +----------+
100 interfacevftbllength ---> +---------------+
102 *******************************************************************************/
105 methodptr *interfacetable[1]; /* interface table (access via macro) */
106 classinfo *class; /* class, the vtbl belongs to */
107 arraydescriptor *arraydesc; /* for array classes, otherwise NULL */
108 s4 vftbllength; /* virtual function table length */
109 s4 interfacetablelength; /* interface table length */
110 s4 baseval; /* base for runtime type check */
111 /* (-index for interfaces) */
112 s4 diffval; /* high - base for runtime type check */
113 s4 *interfacevftbllength; /* length of interface vftbls */
114 methodptr table[1]; /* class vftbl */
118 /* function prototypes ********************************************************/
120 void linker_init(void);
121 classinfo *class_link(classinfo *c);
123 #endif /* _LINKER_H */
127 * These are local overrides for various environment variables in Emacs.
128 * Please do not remove this and leave it at the end of the file, where
129 * Emacs will automagically detect them.
130 * ---------------------------------------------------------------------
133 * indent-tabs-mode: t