| 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 Sensible 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 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. |
| 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 Library General Public License for more details. |
| 21 | .\" |
| 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. |
| 26 | . |
| 27 | .\" Highlight using terminal escapes, rather than overstriking. |
| 28 | .\"\X'tty: sgr 1' |
| 29 | . |
| 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 ); |
| 71 | .PP |
| 72 | .B const void *\c |
| 73 | .B SOD_CLASSOF(\c |
| 74 | .BI "const " cls " *" obj ); |
| 75 | .br |
| 76 | .B void *\c |
| 77 | .B SOD_INSTBASE(\c |
| 78 | .BI "const " cls " *" obj ); |
| 79 | .br |
| 80 | .IB cls " *" \c |
| 81 | .B SOD_CONVERT(\c |
| 82 | .IB cls , |
| 83 | .BI "const void *" obj ); |
| 84 | .br |
| 85 | .B SOD_DECL(\c |
| 86 | .IB cls , |
| 87 | .IB var ); |
| 88 | .PP |
| 89 | .B int |
| 90 | .B sod_subclassp(\c |
| 91 | .BI "const SodClass *" sub , |
| 92 | .BI "const SodClass *" super ); |
| 93 | .br |
| 94 | .B int |
| 95 | .B sod_convert(\c |
| 96 | .BI "const SodClass *" cls , |
| 97 | .BI "const void *" obj ); |
| 98 | . |
| 99 | .\"-------------------------------------------------------------------------- |
| 100 | .SH DESCRIPTION |
| 101 | . |
| 102 | The functions and macros defined here generally expect that |
| 103 | instances and classes inherit from the standard |
| 104 | .B SodObject |
| 105 | root object. |
| 106 | While the translator can (at some effort) support alternative roots, |
| 107 | they will require different run-time support machinery. |
| 108 | . |
| 109 | .SS Infrastructure macros |
| 110 | These macros are mostly intended for use in code |
| 111 | generated by the Sod translator. |
| 112 | Others may find them useful for special effects, |
| 113 | but they can be tricky to understand and use correctly |
| 114 | and can't really be recommended for general use. |
| 115 | .PP |
| 116 | The |
| 117 | .B SOD_XCHAIN |
| 118 | macro performs a `cross-chain upcast'. |
| 119 | Given a pointer |
| 120 | .I cls |
| 121 | .BI * obj |
| 122 | to an instance of a class of type |
| 123 | .I cls |
| 124 | and the nickname |
| 125 | .I chead |
| 126 | of the least specific class in one of |
| 127 | .IR cls 's |
| 128 | superclass chains which does not contain |
| 129 | .I cls |
| 130 | itself, |
| 131 | .B SOD_XCHAIN(\c |
| 132 | .IB chead , |
| 133 | .IB obj ) |
| 134 | returns the address of that chain's storage |
| 135 | within the instance layout as a raw |
| 136 | .B void * |
| 137 | pointer. |
| 138 | (Note that |
| 139 | .I cls |
| 140 | is not mentioned explicitly.) |
| 141 | This macro is used by the generated |
| 142 | .IB CLASS __CONV_ CLS |
| 143 | conversion macros, |
| 144 | which you are encouraged to use instead where possible. |
| 145 | .PP |
| 146 | The |
| 147 | .B SOD_OFFSETDIFF |
| 148 | macro returns the signed offset between |
| 149 | two members of a structure or union type. |
| 150 | Given a structure or union type |
| 151 | .IR type , |
| 152 | and two member names |
| 153 | .I mema |
| 154 | and |
| 155 | .IR memb , |
| 156 | then |
| 157 | .B SOD_OFFSETDIFF(\c |
| 158 | .IB type , |
| 159 | .IB mema , |
| 160 | .IB memb ) |
| 161 | gives the difference, in bytes, |
| 162 | between the objects |
| 163 | .IB x . mema |
| 164 | and |
| 165 | .IB x . memb |
| 166 | for any object |
| 167 | .I x |
| 168 | of type |
| 169 | .IR type . |
| 170 | This macro is used internally when generating vtables |
| 171 | and is not expected to be very useful elsewhere. |
| 172 | .PP |
| 173 | The |
| 174 | .B SOD_ILAYOUT |
| 175 | macro recovers the instance layout base address |
| 176 | from a pointer to one of its instance chains. |
| 177 | Specifically, given a class name |
| 178 | .IR cls , |
| 179 | the nickname |
| 180 | .I chead |
| 181 | of the least specific class in one of |
| 182 | .IR cls 's |
| 183 | superclass chains, |
| 184 | and a pointer |
| 185 | .I obj |
| 186 | to the instance storage for the chain containing |
| 187 | .I chead |
| 188 | within an exact instance of |
| 189 | .I cls |
| 190 | (i.e., not an instance of any proper subclass), |
| 191 | .B SOD_ILAYOUT(\c |
| 192 | .IB cls , |
| 193 | .IB chead , |
| 194 | .IB obj ) |
| 195 | returns the a pointer to the layout structure containing |
| 196 | .IB obj . |
| 197 | This macro is used internally in effective method bodies |
| 198 | and is not expected to be very useful elsewhere |
| 199 | since it's unusual to have such specific knowledge |
| 200 | about the dynamic type of an instance. |
| 201 | The |
| 202 | .B SOD_INSTBASE |
| 203 | macro (described below) is more suited to general use. |
| 204 | . |
| 205 | .SS Utility macros |
| 206 | The following macros are expected to be useful |
| 207 | in Sod method definitions and client code. |
| 208 | .PP |
| 209 | The |
| 210 | .B SOD_CLASSOF |
| 211 | macro returns the class object describing an instance's dynamic class. |
| 212 | Given a pointer |
| 213 | .BI "const " cls " *" obj |
| 214 | to an instance, |
| 215 | .BI SOD_CLASSOF( obj ) |
| 216 | returns a pointer to |
| 217 | .IR obj 's |
| 218 | dynamic class, |
| 219 | which |
| 220 | (assuming |
| 221 | .I obj |
| 222 | is typed correctly in the first place) |
| 223 | will be a subclass of |
| 224 | .IR cls . |
| 225 | (If you wanted the class object for |
| 226 | .I cls |
| 227 | itself, |
| 228 | it's called |
| 229 | .IB cls __class \fR.) |
| 230 | .PP |
| 231 | The |
| 232 | .B SOD_INSTBASE |
| 233 | macro finds the base address of an instance's layout. |
| 234 | Given a pointer |
| 235 | .BI "const " cls " *" obj |
| 236 | to an instance, |
| 237 | .BI SOD_INSTBASE( obj ) |
| 238 | returns the base address of the storage allocated to |
| 239 | .IR obj . |
| 240 | This is useful if you want to free a dynamically allocated instance, |
| 241 | for example. |
| 242 | This macro needs to look up an offset in |
| 243 | .IR obj 's |
| 244 | vtable to do its work. |
| 245 | Compare |
| 246 | .B SOD_ILAYOUT |
| 247 | above, |
| 248 | which is faster but requires |
| 249 | precise knowledge of the instance's dynamic class. |
| 250 | .PP |
| 251 | The |
| 252 | .B SOD_CONVERT |
| 253 | macro performs general conversions |
| 254 | (up-, down-, and cross-casts) on instance pointers. |
| 255 | Given a class name |
| 256 | .I cls |
| 257 | and a pointer |
| 258 | .BI "const void *" obj |
| 259 | to an instance, |
| 260 | .B SOD_CONVERT(\c |
| 261 | .IB cls , |
| 262 | .IB obj ) |
| 263 | returns an appropriately converted pointer to |
| 264 | .I obj |
| 265 | if |
| 266 | .I obj |
| 267 | is indeed an instance of (some subclass of) |
| 268 | .IR cls ; |
| 269 | otherwise it returns a null pointer. |
| 270 | This macro is a simple wrapper around the |
| 271 | .B sod_convert |
| 272 | function described below, |
| 273 | which is useful in the common case that |
| 274 | the target class is known statically. |
| 275 | .PP |
| 276 | The |
| 277 | .B SOD_DECL |
| 278 | macro declares and initializes an instance |
| 279 | with automatic storage duration. |
| 280 | Given a class name |
| 281 | .I cls |
| 282 | and an identifier |
| 283 | .IR var , |
| 284 | .B SOD_DECL(\c |
| 285 | .IB cls , |
| 286 | .IB var ) |
| 287 | declares |
| 288 | .I var |
| 289 | to be a pointer to an instance of |
| 290 | .IR cls . |
| 291 | The instance is initialized in the sense that |
| 292 | its vtable and class pointers have been set up, |
| 293 | and slots for which initializers are defined |
| 294 | are set to the appropriate initial values. |
| 295 | The instance has automatic storage duration: |
| 296 | pointers to it will become invalid when control |
| 297 | exits the scope of the declaration. |
| 298 | . |
| 299 | .SS Functions |
| 300 | The following functions are provided. |
| 301 | .PP |
| 302 | The |
| 303 | .B sod_subclassp |
| 304 | function answers whether one class |
| 305 | .I sub |
| 306 | is actually a subclass of another class |
| 307 | .IR super . |
| 308 | .B sod_subclassp(\c |
| 309 | .IB sub , |
| 310 | .IB super ) |
| 311 | returns nonzero if and only if |
| 312 | .I sub |
| 313 | is a subclass of |
| 314 | .IR super . |
| 315 | This involves a run-time trawl through the class structures: |
| 316 | while some effort has been made to make it perform well |
| 317 | it's still not very fast. |
| 318 | .PP |
| 319 | The |
| 320 | .B sod_convert |
| 321 | function performs general conversions |
| 322 | (up-, down-, and cross-casts) on instance pointers. |
| 323 | Given a class pointer |
| 324 | .I cls |
| 325 | and an instance pointer |
| 326 | .IR obj , |
| 327 | .B sod_convert(\c |
| 328 | .IB cls , |
| 329 | .IB obj ) |
| 330 | returns an appropriately converted pointer to |
| 331 | .I obj |
| 332 | in the case that |
| 333 | .I obj |
| 334 | is an instance of (some subclass of) |
| 335 | .IR cls ; |
| 336 | otherwise it returns null. |
| 337 | This involves a run-time trawl through the class structures: |
| 338 | while some effort has been made to make it perform well |
| 339 | it's still not very fast. |
| 340 | For upcasts (where |
| 341 | .I cls |
| 342 | is a superclass of the static type of |
| 343 | .IR obj ) |
| 344 | the automatically defined conversion macros should be used instead, |
| 345 | because they're much faster and can't fail. |
| 346 | When the target class is known statically, |
| 347 | it's slightly more convenient to use the |
| 348 | .B SOD_CONVERT |
| 349 | macro instead. |
| 350 | . |
| 351 | .\"-------------------------------------------------------------------------- |
| 352 | .SH SEE ALSO |
| 353 | .BR sod (1), |
| 354 | .BR sod-structs (3). |
| 355 | . |
| 356 | .\"-------------------------------------------------------------------------- |
| 357 | .SH AUTHOR |
| 358 | Mark Wooding, <mdw@distorted.org.uk> |
| 359 | . |
| 360 | .\"----- That's all, folks -------------------------------------------------- |