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1 | .\" -*-nroff-*- |
2 | .\" | |
3 | .\" The Sod runtime library | |
4 | .\" | |
5 | .\" (c) 2015 Straylight/Edgeware | |
6 | .\" | |
7 | . | |
8 | .\"----- Licensing notice --------------------------------------------------- | |
9 | .\" | |
10 | .\" This file is part of the Sensble Object Design, an object system for C. | |
11 | .\" | |
12 | .\" SOD is free software; you can redistribute it and/or modify | |
13 | .\" it under the terms of the GNU General Public License as published by | |
14 | .\" the Free Software Foundation; either version 2 of the License, or | |
15 | .\" (at your option) any later version. | |
16 | .\" | |
17 | .\" SOD is distributed in the hope that it will be useful, | |
18 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | .\" GNU General Public License for more details. | |
21 | .\" | |
22 | .\" You should have received a copy of the GNU General Public License | |
23 | .\" along with SOD; if not, write to the Free Software Foundation, | |
24 | .\" Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
25 | . | |
26 | .\"\X'tty: sgr 1' | |
27 | .\" String definitions and font selection. | |
28 | .ie t \{\ | |
29 | . ds o \(bu | |
30 | . if \n(.g .fam P | |
31 | .\} | |
32 | .el \{\ | |
33 | . ds o o | |
34 | .\} | |
35 | . | |
36 | .\" .hP TEXT -- start an indented paragraph with TEXT hanging off to the left | |
37 | .de hP | |
38 | .IP | |
39 | \h'-\w'\fB\\$1\ \fP'u'\fB\\$1\ \fP\c | |
40 | .. | |
41 | . | |
42 | .\"-------------------------------------------------------------------------- | |
43 | .TH sod 3 "8 September 2015" "Straylight/Edgeware" "Sensible Object Design" | |
44 | . | |
45 | .SH NAME | |
46 | sod \- Sensible Object Design runtime library | |
47 | . | |
48 | .\"-------------------------------------------------------------------------- | |
49 | .SH SYNOPSIS | |
50 | .B #include <sod/sod.h> | |
51 | .PP | |
52 | .B void *\c | |
53 | .B SOD_XCHAIN(\c | |
54 | .IB chead , | |
55 | .BI "const " cls " *" obj ); | |
56 | .br | |
57 | .B ptrdiff_t | |
58 | .B SOD_OFFSETDIFF(\c | |
59 | .IB type , | |
60 | .IB mema , | |
61 | .IB memb ); | |
62 | .br | |
63 | .IB cls "__ilayout *" \c | |
64 | .B SOD_ILAYOUT(\c | |
65 | .IB cls , | |
66 | .IB chead , | |
67 | .BI "const void *" obj ); | |
68 | .br | |
69 | .B SOD_CAR(\c | |
70 | .IB arg , | |
71 | .RB ... ); | |
72 | .PP | |
73 | .B const void *\c | |
74 | .B SOD_CLASSOF(\c | |
75 | .BI "const " cls " *" obj ); | |
76 | .br | |
77 | .B void *\c | |
78 | .B SOD_INSTBASE(\c | |
79 | .BI "const " cls " *" obj ); | |
80 | .br | |
81 | .IB cls " *" \c | |
82 | .B SOD_CONVERT(\c | |
83 | .IB cls , | |
84 | .BI "const void *" obj ); | |
85 | .br | |
86 | .B SOD_DECL(\c | |
87 | .IB cls , | |
88 | .IB var ); | |
89 | .PP | |
90 | .B int | |
91 | .B sod_subclassp(\c | |
92 | .BI "const SodClass *" sub , | |
93 | .BI "const SodClass *" super ); | |
94 | .br | |
95 | .B int | |
96 | .B sod_convert(\c | |
97 | .BI "const SodClass *" cls , | |
98 | .BI "const void *" obj ); | |
99 | . | |
100 | .\"-------------------------------------------------------------------------- | |
101 | .SH DESCRIPTION | |
102 | . | |
103 | The functions and macros defined here generally expect that | |
104 | instances and classes inherit from the standard | |
105 | .B SodObject | |
106 | root object. | |
107 | While the translator can (at some effort) support alternative roots, | |
108 | they will require different run-time support machinery. | |
109 | . | |
110 | .SS Infrastructure macros | |
111 | These macros are mostly intended for use in code | |
112 | generated by the Sod translator. | |
113 | Others may find them useful for special effects, | |
114 | but they can be tricky to understand and use correctly | |
115 | and can't really be recommended for general use. | |
116 | .PP | |
117 | The | |
118 | .B SOD_XCHAIN | |
119 | macro performs a `cross-chain upcast'. | |
120 | Given a pointer | |
121 | .I cls | |
122 | .BI * obj | |
123 | to an instance of a class of type | |
124 | .I cls | |
125 | and the nickname | |
126 | .I chead | |
127 | of the least specific class in one of | |
128 | .IR cls 's | |
129 | superclass chains which does not contain | |
130 | .I cls | |
131 | itself, | |
132 | .B SOD_XCHAIN(\c | |
133 | .IB chead , | |
134 | .IB obj ) | |
135 | returns the address of that chain's storage | |
136 | within the instance layout as a raw | |
137 | .B void * | |
138 | pointer. | |
139 | (Note that | |
140 | .I cls | |
141 | is not mentioned explicitly.) | |
142 | This macro is used by the generated | |
143 | .IB CLASS __CONV_ CLS | |
144 | conversion macros, | |
145 | which you are encouraged to use instead where possible. | |
146 | .PP | |
147 | The | |
148 | .B SOD_OFFSETDIFF | |
149 | macro returns the signed offset between | |
150 | two members of a structure or union type. | |
151 | Given a structure or union type | |
152 | .IR type , | |
153 | and two member names | |
154 | .I mema | |
155 | and | |
156 | .IR memb , | |
157 | then | |
158 | .B SOD_OFFSETDIFF(\c | |
159 | .IB type , | |
160 | .IB mema , | |
161 | .IB memb ) | |
162 | gives the difference, in bytes, | |
163 | between the objects | |
164 | .IB x . mema | |
165 | and | |
166 | .IB x . memb | |
167 | for any object | |
168 | .I x | |
169 | of type | |
170 | .IR type . | |
171 | This macro is used internally when generating vtables | |
172 | and is not expected to be very useful elsewhere. | |
173 | .PP | |
174 | The | |
175 | .B SOD_ILAYOUT | |
176 | macro recovers the instance layout base address | |
177 | from a pointer to one of its instance chains. | |
178 | Specifically, given a class name | |
179 | .IR cls , | |
180 | the nickname | |
181 | .I chead | |
182 | of the least specific class in one of | |
183 | .IR cls 's | |
184 | superclass chains, | |
185 | and a pointer | |
186 | .I obj | |
187 | to the instance storage for the chain containing | |
188 | .I chead | |
189 | within an exact instance of | |
190 | .I cls | |
191 | (i.e., not an instance of any proper subclass), | |
192 | .B SOD_ILAYOUT(\c | |
193 | .IB cls , | |
194 | .IB chead , | |
195 | .IB obj ) | |
196 | returns the a pointer to the layout structure containing | |
197 | .IB obj . | |
198 | This macro is used internally in effective method bodies | |
199 | and is not expected to be very useful elsewhere | |
200 | since it's unusual to have such specific knowledge | |
201 | about the dynamic type of an instance. | |
202 | The | |
203 | .B SOD_INSTBASE | |
204 | macro (described below) is more suited to general use. | |
205 | .PP | |
206 | The | |
207 | .B SOD_CAR | |
208 | macro accepts one or more arguments | |
209 | and expands to just its first argument, | |
210 | discarding the others. | |
211 | It is only defined if the C implementation | |
212 | advertises support for C99. | |
213 | It is used in the definitions of message convenience macros | |
214 | for messages which accept a variable number of arguments | |
215 | but no required arguments, | |
216 | and is exported because the author has found such a thing useful in | |
217 | other contexts. | |
218 | . | |
219 | .SS Utility macros | |
220 | The following macros are expected to be useful | |
221 | in Sod method definitions and client code. | |
222 | .PP | |
223 | The | |
224 | .B SOD_CLASSOF | |
225 | macro returns the class object describing an instance's dynamic class. | |
226 | Given a pointer | |
227 | .BI "const " cls " *" obj | |
228 | to an instance, | |
229 | .BI SOD_CLASSOF( obj ) | |
230 | returns a pointer to | |
231 | .IR obj 's | |
232 | dynamic class, | |
233 | which | |
234 | (assuming | |
235 | .I obj | |
236 | is typed correctly in the first place) | |
237 | will be a subclass of | |
238 | .IR cls . | |
239 | (If you wanted the class object for | |
240 | .I cls | |
241 | itself, | |
242 | it's called | |
243 | .IB cls __class \fR.) | |
244 | .PP | |
245 | The | |
246 | .B SOD_INSTBASE | |
247 | macro finds the base address of an instance's layout. | |
248 | Given a pointer | |
249 | .BI "const " cls " *" obj | |
250 | to an instance, | |
251 | .BI SOD_INSTBASE( obj ) | |
252 | returns the base address of the storage allocated to | |
253 | .IR obj . | |
254 | This is useful if you want to free a dynamically allocated instance, | |
255 | for example. | |
256 | This macro needs to look up an offset in | |
257 | .IR obj 's | |
258 | vtable to do its work. | |
259 | Compare | |
260 | .B SOD_ILAYOUT | |
261 | above, | |
262 | which is faster but requires | |
263 | precise knowledge of the instance's dynamic class. | |
264 | .PP | |
265 | The | |
266 | .B SOD_CONVERT | |
267 | macro performs general conversions | |
268 | (up-, down-, and cross-casts) on instance pointers. | |
269 | Given a class name | |
270 | .I cls | |
271 | and a pointer | |
272 | .BI "const void *" obj | |
273 | to an instance, | |
274 | .B SOD_CONVERT(\c | |
275 | .IB cls , | |
276 | .IB obj ) | |
277 | returns an appropriately converted pointer to | |
278 | .I obj | |
279 | if | |
280 | .I obj | |
281 | is indeed an instance of (some subclass of) | |
282 | .IR cls ; | |
283 | otherwise it returns a null pointer. | |
284 | This macro is a simple wrapper around the | |
285 | .B sod_convert | |
286 | function described below, | |
287 | which is useful in the common case that | |
288 | the target class is known statically. | |
289 | .PP | |
290 | The | |
291 | .B SOD_DECL | |
292 | macro declares and initializes an instance | |
293 | with automatic storage duration. | |
294 | Given a class name | |
295 | .I cls | |
296 | and an identifier | |
297 | .IR var , | |
298 | .B SOD_DECL(\c | |
299 | .IB cls , | |
300 | .IB var ) | |
301 | declares | |
302 | .I var | |
303 | to be a pointer to an instance of | |
304 | .IR cls . | |
305 | The instance is initialized in the sense that | |
306 | its vtable and class pointers have been set up, | |
307 | and slots for which initializers are defined | |
308 | are set to the appropriate initial values. | |
309 | The instance has automatic storage duration: | |
310 | pointers to it will become invalid when control | |
311 | exits the scope of the declaration. | |
312 | . | |
313 | .SS Functions | |
314 | The following functions are provided. | |
315 | .PP | |
316 | The | |
317 | .B sod_subclassp | |
318 | function answers whether one class | |
319 | .I sub | |
320 | is actually a subclass of another class | |
321 | .IR super . | |
322 | .B sod_subclassp(\c | |
323 | .IB sub , | |
324 | .IB super ) | |
325 | returns nonzero if and only if | |
326 | .I sub | |
327 | is a subclass of | |
328 | .IR super . | |
329 | This involves a run-time trawl through the class structures: | |
330 | while some effort has been made to make it perform well | |
331 | it's still not very fast. | |
332 | .PP | |
333 | The | |
334 | .B sod_convert | |
335 | function performs general conversions | |
336 | (up-, down-, and cross-casts) on instance pointers. | |
337 | Given a class pointer | |
338 | .I cls | |
339 | and an instance pointer | |
340 | .IR obj , | |
341 | .B sod_convert(\c | |
342 | .IB cls , | |
343 | .IB obj ) | |
344 | returns an appropriately converted pointer to | |
345 | .I obj | |
346 | in the case that | |
347 | .I obj | |
348 | is an instance of (some subclass of) | |
349 | .IR cls ; | |
350 | otherwise it returns null. | |
351 | This involves a run-time trawl through the class structures: | |
352 | while some effort has been made to make it perform well | |
353 | it's still not very fast. | |
354 | For upcasts (where | |
355 | .I cls | |
356 | is a superclass of the static type of | |
357 | .IR obj ) | |
358 | the automatically defined conversion macros should be used instead, | |
359 | because they're much faster and can't fail. | |
360 | When the target class is known statically, | |
361 | it's slightly more convenient to use the | |
362 | .B SOD_CONVERT | |
363 | macro instead. | |
364 | . | |
365 | .\"-------------------------------------------------------------------------- | |
366 | .SH SEE ALSO | |
367 | .BR sod-structs (3). | |
368 | . | |
369 | .\"-------------------------------------------------------------------------- | |
370 | .SH AUTHOR | |
371 | Mark Wooding, <mdw@distorted.org.uk> | |
372 | . | |
373 | .\"----- That's all, folks -------------------------------------------------- |