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1 | /* -*-c-*- |
2 | * | |
3 | * Sensible Object Design header file | |
4 | * | |
5 | * (c) 2009 Straylight/Edgeware | |
6 | */ | |
7 | ||
8 | /*----- Licensing notice --------------------------------------------------* | |
9 | * | |
e0808c47 | 10 | * This file is part of the Sensible Object Design, an object system for C. |
1f1d88f5 | 11 | * |
7d21069e MW |
12 | * The SOD Runtime Library is free software; you can redistribute it and/or |
13 | * modify it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
1f1d88f5 | 16 | * |
7d21069e | 17 | * The SOD Runtime is distributed in the hope that it will be useful, |
1f1d88f5 MW |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
7d21069e | 20 | * GNU Library General Public License for more details. |
1f1d88f5 | 21 | * |
7d21069e MW |
22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with SOD; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
1f1d88f5 MW |
26 | */ |
27 | ||
28 | #ifndef SOD_H | |
29 | #define SOD_H | |
30 | ||
31 | #ifdef __cplusplus | |
32 | extern "C" { | |
33 | #endif | |
34 | ||
68a4f8c9 MW |
35 | /*----- Preliminary utilities ---------------------------------------------*/ |
36 | ||
37 | /* --- @SOD__CAR@ --- * | |
38 | * | |
39 | * Arguments: @...@ = a nonempty list of arguments | |
40 | * | |
41 | * Returns: The first argument only. | |
42 | */ | |
43 | ||
44 | #if __STDC_VERSION__ >= 199901 | |
45 | # define SOD__CAR(...) SOD__CARx(__VA_LIST__, _) | |
46 | # define SOD__CARx(a, ...) a | |
47 | #endif | |
48 | ||
1f1d88f5 MW |
49 | /*----- Header files ------------------------------------------------------*/ |
50 | ||
51 | #include <stdarg.h> | |
52 | #include <stddef.h> | |
53 | ||
ddee4bb1 | 54 | #include "sod-base.h" |
1f1d88f5 MW |
55 | |
56 | /*----- Data structures ---------------------------------------------------*/ | |
57 | ||
58 | /* A skeletal vtable structure. At the beginning of every ichain is a | |
59 | * pointer to one of these. | |
60 | */ | |
61 | struct sod_vtable { | |
dea4d055 | 62 | const SodClass *_class; /* Pointer to class object */ |
1f1d88f5 MW |
63 | size_t _base; /* Offset to instance base */ |
64 | }; | |
65 | ||
66 | /* A skeletal instance structure. Every instance pointer points to one of | |
67 | * these. | |
68 | */ | |
69 | struct sod_instance { | |
d83a91c6 | 70 | const struct sod_vtable *_vt; /* Pointer to (chain's) vtable */ |
1f1d88f5 MW |
71 | }; |
72 | ||
73 | /* Information about a particular chain of superclasses. In each class, | |
74 | * there's a pointer to an array of these. If you search hard enough, you'll | |
75 | * be able to find out a fair amount of information about an instance and its | |
76 | * class. | |
77 | */ | |
78 | struct sod_chain { | |
79 | size_t n_classes; /* Number of classes in chain */ | |
80 | const SodClass *const *classes; /* Vector of classes, head first */ | |
81 | size_t off_ichain; /* Offset of ichain from base */ | |
82 | const struct sod_vtable *vt; /* Chain's vtable pointer */ | |
83 | size_t ichainsz; /* Size of the ichain structure */ | |
84 | }; | |
85 | ||
86 | /*----- Infrastructure macros ---------------------------------------------*/ | |
87 | ||
88 | /* --- @SOD_XCHAIN@ --- * | |
89 | * | |
90 | * Arguments: @chead@ = nickname of target chain's head | |
6a590fd0 | 91 | * @obj@ = pointer to an instance chain |
1f1d88f5 | 92 | * |
664b3951 | 93 | * Returns: Pointer to target chain, as a @void *@. |
1f1d88f5 MW |
94 | * |
95 | * Use: Utility for implementing cross-chain upcasts. It's probably | |
96 | * not that clever to use this macro directly; it's used to make | |
97 | * the automatically-generated upcast macros more palatable. | |
98 | */ | |
99 | ||
664b3951 MW |
100 | #define SOD_XCHAIN(chead, obj) \ |
101 | ((void *)((char *)(obj) + (obj)->_vt->_off_##chead)) | |
1f1d88f5 | 102 | |
a07d8d00 MW |
103 | /* --- @SOD_OFFSETDIFF@ --- * |
104 | * | |
105 | * Arguments: @type@ = a simple (i.e., declaratorless) type name | |
106 | * @mema, memb@ = members of @type@ | |
107 | * | |
108 | * Returns: The relative offset from @mema@ to @memb@, as a @ptrdiff_t@. | |
109 | * | |
110 | * Use: Computes a signed offset between structure members. | |
111 | */ | |
112 | ||
113 | #define SOD_OFFSETDIFF(type, mema, memb) \ | |
114 | ((ptrdiff_t)offsetof(type, memb) - (ptrdiff_t)offsetof(type, mema)) | |
115 | ||
1f1d88f5 MW |
116 | /* --- @SOD_ILAYOUT@ --- * |
117 | * | |
118 | * Arguments: @cls@ = name of a class | |
119 | * @chead@ = nickname of chain head of @cls@ | |
6a590fd0 MW |
120 | * @obj@ = pointer to the @chead@ ichain of an (exact) instance |
121 | * of @cls@ | |
1f1d88f5 MW |
122 | * |
123 | * Returns: A pointer to the instance's base, cast as a pointer to the | |
124 | * ilayout structure. | |
125 | * | |
126 | * Use: Finds an instance's base address given a pointer to one of | |
127 | * its ichains, if you know precisely the instance's class and | |
45c53484 MW |
128 | * which chain you're pointing to. If you don't, then (a) you |
129 | * want @SOD_INSTBASE@ below, and (b) you'll have the wrong | |
1f1d88f5 MW |
130 | * ilayout anyway. |
131 | * | |
132 | * This macro is not intended to be used directly outside of | |
133 | * automatically generated effective method and trampoline | |
134 | * functions, which have the kinds of specific knowledge | |
135 | * necessary to use it safely. | |
136 | */ | |
137 | ||
6a590fd0 | 138 | #define SOD_ILAYOUT(cls, chead, obj) \ |
1f1d88f5 | 139 | ((struct cls##__ilayout *) \ |
6a590fd0 MW |
140 | ((char *)(obj) - offsetof(struct cls##__ilayout, chead))) |
141 | ||
142 | /*----- Utility macros ----------------------------------------------------*/ | |
143 | ||
144 | /* --- @SOD_CLASSOF@ --- * | |
145 | * | |
146 | * Arguments: @p@ = pointer to an instance chain | |
147 | * | |
cb9f1e5e | 148 | * Returns: A pointer to the instance's class, as a @const SodClass *@. |
6a590fd0 MW |
149 | */ |
150 | ||
151 | #define SOD_CLASSOF(obj) ((const SodClass *)(obj)->_vt->_class) | |
1f1d88f5 | 152 | |
45c53484 MW |
153 | /* --- @SOD_INSTBASE@ --- * |
154 | * | |
6a590fd0 MW |
155 | * Arguments: @obj@ = pointer to an instance (i.e., the address of one of |
156 | * its instance chains) | |
45c53484 | 157 | * |
6a590fd0 | 158 | * Returns: The base address of @obj@'s instance layout, as a @void *@. |
45c53484 MW |
159 | * |
160 | * Use: Finds the base address of an instance. If you know the | |
161 | * dynamic class of the object then @SOD_ILAYOUT@ is faster. If | |
162 | * you don't, this is the right macro, but your options for | |
163 | * doing something sensible with the result are limited, mostly | |
164 | * to simple memory management operations such as freeing or | |
165 | * zeroizing the instance structure. | |
166 | */ | |
167 | ||
6a590fd0 | 168 | #define SOD_INSTBASE(obj) ((void *)((char *)(obj) - (obj)->_vt->_base)) |
77027cca | 169 | |
6a590fd0 | 170 | /* --- @SOD_CONVERT@ --- * |
77027cca | 171 | * |
6a590fd0 MW |
172 | * Arguments: @cls@ = a class type name |
173 | * @const void *obj@ = a pointer to an instance | |
77027cca | 174 | * |
6a590fd0 MW |
175 | * Returns: Pointer to appropriate instance ichain, or null if the |
176 | * instance isn't of the specified class. | |
177 | * | |
178 | * Use: This is a simple wrapper around the @sod_convert@, which | |
179 | * you should see for full details. It accepts a class type | |
180 | * name rather than a pointer to a class object, and arranges to | |
181 | * return a pointer of the correct type. | |
77027cca MW |
182 | */ |
183 | ||
6a590fd0 | 184 | #define SOD_CONVERT(cls, obj) ((cls *)sod_convert(cls##__class, (obj))) |
77027cca | 185 | |
267dd3e7 MW |
186 | /* --- @SOD_DECL@ --- * |
187 | * | |
188 | * Arguments: @cls_@ = a class type name | |
189 | * @var_@ = a variable name | |
190 | * | |
191 | * Use: Declare @var_@ as a pointer to an initialized instance of | |
192 | * @cls_@ with automatic lifetime. | |
193 | */ | |
194 | ||
195 | #define SOD_DECL(cls_, var_) \ | |
196 | struct cls_##__ilayout var_##__layout; \ | |
197 | cls_ *var_ = cls_##__class->cls.init(&var_##__layout) | |
198 | ||
1f1d88f5 MW |
199 | /*----- Functions provided ------------------------------------------------*/ |
200 | ||
77027cca MW |
201 | /* --- @sod_subclassp@ --- * |
202 | * | |
dea4d055 | 203 | * Arguments: @const SodClass *sub, *super@ = pointers to two classes |
77027cca MW |
204 | * |
205 | * Returns: Nonzero if @c@ is a subclass of @d@. | |
206 | */ | |
207 | ||
dea4d055 | 208 | extern int sod_subclassp(const SodClass */*sub*/, const SodClass */*super*/); |
77027cca | 209 | |
1f1d88f5 MW |
210 | /* --- @sod_convert@ --- * |
211 | * | |
212 | * Arguments: @const SodClass *cls@ = desired class object | |
213 | * @const void *obj@ = pointer to instance | |
214 | * | |
215 | * Returns: Pointer to appropriate ichain of object, or null if the | |
216 | * instance isn't of the specified class. | |
217 | * | |
218 | * Use: General down/cross-casting function. | |
219 | * | |
220 | * Upcasts can be performed efficiently using the automatically | |
dea4d055 | 221 | * generated macros. In particular, upcasts within a chain are |
1f1d88f5 MW |
222 | * trivial; cross-chain upcasts require information from vtables |
223 | * but are fairly fast. This function is rather slower, but is | |
224 | * much more general. | |
225 | * | |
226 | * Suppose we have an instance of a class C, referred to by a | |
dea4d055 | 227 | * pointer to an instance of one of C's superclasses S. If T |
1f1d88f5 | 228 | * is some other superclass of C then this function will return |
dea4d055 | 229 | * a pointer to C suitable for use as an instance of T. If T |
1f1d88f5 MW |
230 | * is not a superclass of C, then the function returns null. |
231 | * (If the pointer doesn't point to an instance of some class | |
232 | * then the behaviour is undefined.) Note that you don't need | |
dea4d055 | 233 | * to know what either C or S actually are. |
1f1d88f5 MW |
234 | */ |
235 | ||
6a590fd0 | 236 | extern void *sod_convert(const SodClass */*cls*/, const void */*obj*/); |
1f1d88f5 MW |
237 | |
238 | /*----- That's all, folks -------------------------------------------------*/ | |
239 | ||
240 | #ifdef __cplusplus | |
241 | } | |
242 | #endif | |
243 | ||
244 | #endif |