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1 | .\" -*-nroff-*- |
2 | .\" | |
3 | .\" The Sod runtime library | |
4 | .\" | |
5 | .\" (c) 2015 Straylight/Edgeware | |
6 | .\" | |
7 | . | |
8 | .\"----- Licensing notice --------------------------------------------------- | |
9 | .\" | |
e0808c47 | 10 | .\" This file is part of the Sensible Object Design, an object system for C. |
47de28ae MW |
11 | .\" |
12 | .\" SOD is free software; you can redistribute it and/or modify | |
65aaa02c MW |
13 | .\" 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. | |
47de28ae MW |
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 | |
65aaa02c | 20 | .\" GNU Library General Public License for more details. |
47de28ae | 21 | .\" |
65aaa02c 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. | |
47de28ae | 26 | . |
9ed8eb2a | 27 | .\" Highlight using terminal escapes, rather than overstriking. |
47de28ae | 28 | .\"\X'tty: sgr 1' |
9ed8eb2a | 29 | . |
47de28ae MW |
30 | .\" String definitions and font selection. |
31 | .ie t \{\ | |
32 | . ds o \(bu | |
33 | . if \n(.g .fam P | |
34 | .\} | |
35 | .el \{\ | |
36 | . ds o o | |
37 | .\} | |
38 | . | |
39 | .\" .hP TEXT -- start an indented paragraph with TEXT hanging off to the left | |
40 | .de hP | |
41 | .IP | |
42 | \h'-\w'\fB\\$1\ \fP'u'\fB\\$1\ \fP\c | |
43 | .. | |
44 | . | |
45 | .\"-------------------------------------------------------------------------- | |
46 | .TH sod 3 "8 September 2015" "Straylight/Edgeware" "Sensible Object Design" | |
47 | . | |
48 | .SH NAME | |
49 | sod \- Sensible Object Design runtime library | |
50 | . | |
51 | .\"-------------------------------------------------------------------------- | |
52 | .SH SYNOPSIS | |
53 | .B #include <sod/sod.h> | |
54 | .PP | |
55 | .B void *\c | |
56 | .B SOD_XCHAIN(\c | |
57 | .IB chead , | |
58 | .BI "const " cls " *" obj ); | |
59 | .br | |
60 | .B ptrdiff_t | |
61 | .B SOD_OFFSETDIFF(\c | |
62 | .IB type , | |
63 | .IB mema , | |
64 | .IB memb ); | |
65 | .br | |
66 | .IB cls "__ilayout *" \c | |
67 | .B SOD_ILAYOUT(\c | |
68 | .IB cls , | |
69 | .IB chead , | |
70 | .BI "const void *" obj ); | |
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71 | .br |
72 | .B void *\c | |
73 | .B SOD_INSTBASE(\c | |
74 | .BI "const " cls " *" obj ); | |
47de28ae | 75 | .PP |
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76 | .B const void *\c |
77 | .B SOD_CLASSOF(\c | |
78 | .BI "const " cls " *" obj ); | |
79 | .br | |
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80 | .B int |
81 | .B sod_subclassp(\c | |
82 | .BI "const SodClass *" sub , | |
83 | .BI "const SodClass *" super ); | |
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84 | .PP |
85 | .IB cls " *" \c | |
86 | .B SOD_CONVERT(\c | |
87 | .IB cls , | |
88 | .BI "const void *" obj ); | |
47de28ae MW |
89 | .br |
90 | .B int | |
91 | .B sod_convert(\c | |
92 | .BI "const SodClass *" cls , | |
93 | .BI "const void *" obj ); | |
4e3a7cb2 | 94 | .PP |
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95 | .IB cls " *" \c |
96 | .B SOD_INIT(\c | |
97 | .IB cls , | |
98 | .BI "void *" p , | |
99 | .IB keywords ); | |
100 | .br | |
101 | .B void *\c | |
102 | .B sod_init(\c | |
103 | .BI "const SodClass *" cls , | |
104 | .BI "void *" p , | |
105 | .B ...); | |
106 | .br | |
107 | .B void *\c | |
108 | .B sod_initv(\c | |
109 | .BI "const SodClass *" cls , | |
110 | .BI "void *" p , | |
111 | .BI "va_list " ap ); | |
112 | .br | |
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113 | .B SOD_DECL(\c |
114 | .IB cls , | |
115 | .IB var ); | |
116 | .PP | |
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117 | . |
118 | .\"-------------------------------------------------------------------------- | |
119 | .SH DESCRIPTION | |
120 | . | |
121 | The functions and macros defined here generally expect that | |
122 | instances and classes inherit from the standard | |
123 | .B SodObject | |
124 | root object. | |
125 | While the translator can (at some effort) support alternative roots, | |
126 | they will require different run-time support machinery. | |
127 | . | |
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128 | .SS Layout utilities |
129 | The following macros are useful in | |
130 | finding one's way around an instance layout structure, | |
131 | given various levels of information about | |
132 | what kind of object one is dealing with, | |
133 | or for computing the tables which are used for | |
134 | this kind of navigation. | |
135 | .PP | |
136 | These macros are mostly intended for use in | |
137 | code generated by the Sod translator. | |
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138 | Others may find them useful for special effects, |
139 | but they can be tricky to understand and use correctly | |
140 | and can't really be recommended for general use. | |
141 | .PP | |
142 | The | |
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143 | .B SOD_OFFSETDIFF |
144 | macro returns the signed offset between | |
145 | two members of a structure or union type. | |
146 | Given a structure or union type | |
147 | .IR type , | |
148 | and two member names | |
149 | .I mema | |
150 | and | |
151 | .IR memb , | |
152 | then | |
153 | .B SOD_OFFSETDIFF(\c | |
154 | .IB type , | |
155 | .IB mema , | |
156 | .IB memb ) | |
157 | gives the difference, in bytes, | |
158 | between the objects | |
159 | .IB x . mema | |
160 | and | |
161 | .IB x . memb | |
162 | for any object | |
163 | .I x | |
164 | of type | |
165 | .IR type . | |
166 | This macro is used internally when generating vtables | |
167 | and is not expected to be very useful elsewhere. | |
168 | .PP | |
169 | The | |
170 | .B SOD_ILAYOUT | |
171 | macro recovers the instance layout base address | |
172 | from a pointer to one of its instance chains. | |
173 | Specifically, given a class name | |
174 | .IR cls , | |
175 | the nickname | |
176 | .I chead | |
177 | of the least specific class in one of | |
178 | .IR cls 's | |
179 | superclass chains, | |
180 | and a pointer | |
181 | .I obj | |
182 | to the instance storage for the chain containing | |
183 | .I chead | |
184 | within an exact instance of | |
185 | .I cls | |
186 | (i.e., not an instance of any proper subclass), | |
187 | .B SOD_ILAYOUT(\c | |
188 | .IB cls , | |
189 | .IB chead , | |
190 | .IB obj ) | |
191 | returns the a pointer to the layout structure containing | |
192 | .IB obj . | |
193 | This macro is used internally in effective method bodies | |
194 | and is not expected to be very useful elsewhere | |
195 | since it's unusual to have such specific knowledge | |
196 | about the dynamic type of an instance. | |
197 | The | |
198 | .B SOD_INSTBASE | |
199 | macro (described below) is more suited to general use. | |
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200 | .PP |
201 | The | |
202 | .B SOD_INSTBASE | |
203 | macro finds the base address of an instance's layout. | |
204 | Given a pointer | |
205 | .BI "const " cls " *" obj | |
206 | to an instance, | |
207 | .BI SOD_INSTBASE( obj ) | |
208 | returns the base address of the storage allocated to | |
209 | .IR obj . | |
210 | This is useful if you want to free a dynamically allocated instance, | |
211 | for example. | |
212 | This macro needs to look up an offset in | |
213 | .IR obj 's | |
214 | vtable to do its work. | |
215 | Compare | |
216 | .B SOD_ILAYOUT | |
217 | above, | |
218 | which is faster but requires | |
219 | precise knowledge of the instance's dynamic class. | |
47de28ae | 220 | . |
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221 | .SS Classes |
222 | The following macros and functions | |
223 | query the runtime relationhips between | |
224 | instances and classes. | |
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225 | .PP |
226 | The | |
227 | .B SOD_CLASSOF | |
228 | macro returns the class object describing an instance's dynamic class. | |
229 | Given a pointer | |
230 | .BI "const " cls " *" obj | |
231 | to an instance, | |
232 | .BI SOD_CLASSOF( obj ) | |
233 | returns a pointer to | |
234 | .IR obj 's | |
235 | dynamic class, | |
236 | which | |
237 | (assuming | |
238 | .I obj | |
239 | is typed correctly in the first place) | |
240 | will be a subclass of | |
241 | .IR cls . | |
242 | (If you wanted the class object for | |
243 | .I cls | |
244 | itself, | |
245 | it's called | |
246 | .IB cls __class \fR.) | |
247 | .PP | |
248 | The | |
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249 | .B sod_subclassp |
250 | function answers whether one class | |
251 | .I sub | |
252 | is actually a subclass of another class | |
253 | .IR super . | |
254 | .B sod_subclassp(\c | |
255 | .IB sub , | |
256 | .IB super ) | |
257 | returns nonzero if and only if | |
258 | .I sub | |
259 | is a subclass of | |
260 | .IR super . | |
261 | This involves a run-time trawl through the class structures: | |
262 | while some effort has been made to make it perform well | |
263 | it's still not very fast. | |
264 | . | |
265 | .SS Conversions | |
266 | The following macros and functions are used | |
267 | to convert instance pointers of some (static) type | |
268 | into instance pointers of other static types | |
269 | to the same instance. | |
270 | .PP | |
271 | The | |
272 | .B SOD_XCHAIN | |
273 | macro performs a `cross-chain upcast'. | |
47de28ae | 274 | Given a pointer |
4e3a7cb2 MW |
275 | .I cls |
276 | .BI * obj | |
277 | to an instance of a class of type | |
278 | .I cls | |
279 | and the nickname | |
280 | .I chead | |
281 | of the least specific class in one of | |
282 | .IR cls 's | |
283 | superclass chains which does not contain | |
284 | .I cls | |
285 | itself, | |
286 | .B SOD_XCHAIN(\c | |
287 | .IB chead , | |
288 | .IB obj ) | |
289 | returns the address of that chain's storage | |
290 | within the instance layout as a raw | |
291 | .B void * | |
292 | pointer. | |
293 | (Note that | |
294 | .I cls | |
295 | is not mentioned explicitly.) | |
296 | This macro is used by the generated | |
297 | .IB cls __CONV_ c | |
298 | conversion macros, | |
299 | which you are encouraged to use instead where possible. | |
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300 | .PP |
301 | The | |
302 | .B SOD_CONVERT | |
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303 | macro |
304 | and | |
305 | .B sod_convert | |
306 | function | |
307 | perform general conversions | |
47de28ae | 308 | (up-, down-, and cross-casts) on instance pointers. |
4e3a7cb2 | 309 | Given a class |
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310 | .I cls |
311 | and a pointer | |
312 | .BI "const void *" obj | |
313 | to an instance, | |
4e3a7cb2 | 314 | they return an appropriately converted pointer to |
47de28ae MW |
315 | .I obj |
316 | if | |
317 | .I obj | |
318 | is indeed an instance of (some subclass of) | |
319 | .IR cls ; | |
4e3a7cb2 MW |
320 | otherwise they return a null pointer. |
321 | .PP | |
322 | The | |
323 | .B SOD_CONVERT | |
324 | macro expects | |
325 | .I cls | |
326 | to be a class name; | |
327 | the | |
328 | .B sod_convert | |
329 | function | |
330 | expects a pointer to a class object instead. | |
331 | .PP | |
332 | This involves a run-time trawl through the class structures: | |
333 | while some effort has been made to make it perform well | |
334 | it's still not very fast. | |
335 | For upcasts (where | |
336 | .I cls | |
337 | is a superclass of the static type of | |
338 | .IR obj ) | |
339 | the automatically defined conversion macros should be used instead, | |
340 | because they're much faster and can't fail. | |
341 | .PP | |
342 | When the target class is known statically, | |
343 | it's slightly more convenient to use the | |
344 | .B SOD_CONVERT | |
345 | macro rather than the | |
47de28ae | 346 | .B sod_convert |
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347 | function, |
348 | since the class object name is longer and uglier, | |
349 | and the macro returns a pointer of the correct type. | |
350 | . | |
351 | .SS Instance lifecycle | |
352 | The following macros and functions | |
353 | manage the standard steps along | |
354 | an instance's lifecycle. | |
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355 | .PP |
356 | The | |
a142609c MW |
357 | .B SOD_INIT |
358 | macro, | |
359 | and the | |
360 | .B sod_init | |
361 | and | |
362 | .B sod_initv | |
363 | functions, | |
364 | imprint and initialize an instance of a class | |
365 | .I cls | |
366 | in the storage starting at address | |
367 | .IR p . | |
368 | .PP | |
369 | The direct class for the new instance is specified as | |
370 | a class name to | |
371 | .BR SOD_INIT , | |
372 | or a pointer to a class object to the functions. | |
373 | .PP | |
374 | Keyword arguments for the initialization message may be provided. | |
375 | The | |
376 | .B SOD_INIT | |
377 | macro expects a single preprocessor-time argument | |
378 | which is a use of one of | |
379 | .B KWARGS | |
380 | or | |
381 | .B NO_KWARGS | |
382 | (see | |
383 | .BR keyword (3)); | |
384 | the | |
385 | .B sod_init | |
386 | function expects the keywords as | |
387 | a variable-length argument tail; | |
388 | and | |
389 | .B sod_initv | |
390 | expects the keywords to be passed indirectly, | |
391 | through the captured argument-tail cursor | |
392 | .IR ap . | |
393 | .PP | |
394 | The return value is an instance pointer for the class | |
395 | .IR cls ; | |
396 | the | |
397 | .B SOD_INIT | |
398 | macro will have converted it to the correct type, | |
399 | so it should probably be used where possible. | |
400 | In fact, this is guaranteed to be equal to | |
401 | .I p | |
402 | by the layout rules described in | |
403 | .BR sod-structs (3). | |
404 | .PP | |
405 | The | |
47de28ae MW |
406 | .B SOD_DECL |
407 | macro declares and initializes an instance | |
408 | with automatic storage duration. | |
409 | Given a class name | |
410 | .I cls | |
411 | and an identifier | |
412 | .IR var , | |
413 | .B SOD_DECL(\c | |
414 | .IB cls , | |
415 | .IB var ) | |
416 | declares | |
417 | .I var | |
418 | to be a pointer to an instance of | |
419 | .IR cls . | |
420 | The instance is initialized in the sense that | |
421 | its vtable and class pointers have been set up, | |
422 | and slots for which initializers are defined | |
423 | are set to the appropriate initial values. | |
424 | The instance has automatic storage duration: | |
425 | pointers to it will become invalid when control | |
426 | exits the scope of the declaration. | |
427 | . | |
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428 | .\"-------------------------------------------------------------------------- |
429 | .SH SEE ALSO | |
a142609c | 430 | .BR keyword (3), |
9ed8eb2a | 431 | .BR sod (1), |
47de28ae MW |
432 | .BR sod-structs (3). |
433 | . | |
434 | .\"-------------------------------------------------------------------------- | |
435 | .SH AUTHOR | |
436 | Mark Wooding, <mdw@distorted.org.uk> | |
437 | . | |
438 | .\"----- That's all, folks -------------------------------------------------- |