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88e17b57 | 1 | /* GNU Objective C Runtime class related functions |
40165636 RB |
2 | Copyright (C) 1993, 1995, 1996, 1997, 2001, 2002 |
3 | Free Software Foundation, Inc. | |
88e17b57 BE |
4 | Contributed by Kresten Krab Thorup and Dennis Glatting. |
5 | ||
2726bdba NP |
6 | Lock-free class table code designed and written from scratch by |
7 | Nicola Pero, 2001. | |
8 | ||
6c82ad25 | 9 | This file is part of GCC. |
88e17b57 | 10 | |
6c82ad25 | 11 | GCC is free software; you can redistribute it and/or modify it under the |
88e17b57 BE |
12 | terms of the GNU General Public License as published by the Free Software |
13 | Foundation; either version 2, or (at your option) any later version. | |
14 | ||
6c82ad25 | 15 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY |
88e17b57 BE |
16 | WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS |
17 | FOR A PARTICULAR PURPOSE. See the GNU General Public License for more | |
18 | details. | |
19 | ||
20 | You should have received a copy of the GNU General Public License along with | |
6c82ad25 | 21 | GCC; see the file COPYING. If not, write to the Free Software |
88e17b57 BE |
22 | Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ |
23 | ||
24 | /* As a special exception, if you link this library with files compiled with | |
25 | GCC to produce an executable, this does not cause the resulting executable | |
26 | to be covered by the GNU General Public License. This exception does not | |
27 | however invalidate any other reasons why the executable file might be | |
28 | covered by the GNU General Public License. */ | |
29 | ||
2726bdba NP |
30 | /* |
31 | The code in this file critically affects class method invocation | |
32 | speed. This long preamble comment explains why, and the issues | |
33 | involved. | |
34 | ||
35 | ||
36 | One of the traditional weaknesses of the GNU Objective-C runtime is | |
37 | that class method invocations are slow. The reason is that when you | |
38 | write | |
39 | ||
40 | array = [NSArray new]; | |
41 | ||
42 | this gets basically compiled into the equivalent of | |
43 | ||
44 | array = [(objc_get_class ("NSArray")) new]; | |
45 | ||
46 | objc_get_class returns the class pointer corresponding to the string | |
47 | `NSArray'; and because of the lookup, the operation is more | |
48 | complicated and slow than a simple instance method invocation. | |
49 | ||
50 | Most high performance Objective-C code (using the GNU Objc runtime) | |
51 | I had the opportunity to read (or write) work around this problem by | |
52 | caching the class pointer: | |
53 | ||
54 | Class arrayClass = [NSArray class]; | |
55 | ||
56 | ... later on ... | |
57 | ||
58 | array = [arrayClass new]; | |
59 | array = [arrayClass new]; | |
60 | array = [arrayClass new]; | |
61 | ||
62 | In this case, you always perform a class lookup (the first one), but | |
63 | then all the [arrayClass new] methods run exactly as fast as an | |
64 | instance method invocation. It helps if you have many class method | |
65 | invocations to the same class. | |
66 | ||
67 | The long-term solution to this problem would be to modify the | |
68 | compiler to output tables of class pointers corresponding to all the | |
69 | class method invocations, and to add code to the runtime to update | |
70 | these tables - that should in the end allow class method invocations | |
71 | to perform precisely as fast as instance method invocations, because | |
72 | no class lookup would be involved. I think the Apple Objective-C | |
73 | runtime uses this technique. Doing this involves synchronized | |
74 | modifications in the runtime and in the compiler. | |
75 | ||
76 | As a first medicine to the problem, I [NP] have redesigned and | |
77 | rewritten the way the runtime is performing class lookup. This | |
78 | doesn't give as much speed as the other (definitive) approach, but | |
79 | at least a class method invocation now takes approximately 4.5 times | |
80 | an instance method invocation on my machine (it would take approx 12 | |
81 | times before the rewriting), which is a lot better. | |
82 | ||
83 | One of the main reason the new class lookup is so faster is because | |
84 | I implemented it in a way that can safely run multithreaded without | |
85 | using locks - a so-called `lock-free' data structure. The atomic | |
86 | operation is pointer assignment. The reason why in this problem | |
87 | lock-free data structures work so well is that you never remove | |
88 | classes from the table - and the difficult thing with lock-free data | |
89 | structures is freeing data when is removed from the structures. */ | |
90 | ||
91 | #include "runtime.h" /* the kitchen sink */ | |
88e17b57 BE |
92 | #include "sarray.h" |
93 | ||
2726bdba NP |
94 | #include <objc/objc.h> |
95 | #include <objc/objc-api.h> | |
96 | #include <objc/thr.h> | |
97 | ||
98 | /* We use a table which maps a class name to the corresponding class | |
99 | * pointer. The first part of this file defines this table, and | |
100 | * functions to do basic operations on the table. The second part of | |
101 | * the file implements some higher level Objective-C functionality for | |
102 | * classes by using the functions provided in the first part to manage | |
103 | * the table. */ | |
104 | ||
105 | /** | |
106 | ** Class Table Internals | |
107 | **/ | |
108 | ||
109 | /* A node holding a class */ | |
110 | typedef struct class_node | |
111 | { | |
112 | struct class_node *next; /* Pointer to next entry on the list. | |
113 | NULL indicates end of list. */ | |
114 | ||
115 | const char *name; /* The class name string */ | |
116 | int length; /* The class name string length */ | |
117 | Class pointer; /* The Class pointer */ | |
118 | ||
119 | } *class_node_ptr; | |
120 | ||
121 | /* A table containing classes is a class_node_ptr (pointing to the | |
122 | first entry in the table - if it is NULL, then the table is | |
123 | empty). */ | |
124 | ||
125 | /* We have 1024 tables. Each table contains all class names which | |
126 | have the same hash (which is a number between 0 and 1023). To look | |
127 | up a class_name, we compute its hash, and get the corresponding | |
128 | table. Once we have the table, we simply compare strings directly | |
129 | till we find the one which we want (using the length first). The | |
130 | number of tables is quite big on purpose (a normal big application | |
131 | has less than 1000 classes), so that you shouldn't normally get any | |
132 | collisions, and get away with a single comparison (which we can't | |
133 | avoid since we need to know that you have got the right thing). */ | |
134 | #define CLASS_TABLE_SIZE 1024 | |
135 | #define CLASS_TABLE_MASK 1023 | |
136 | ||
137 | static class_node_ptr class_table_array[CLASS_TABLE_SIZE]; | |
138 | ||
139 | /* The table writing mutex - we lock on writing to avoid conflicts | |
140 | between different writers, but we read without locks. That is | |
141 | possible because we assume pointer assignment to be an atomic | |
142 | operation. */ | |
143 | static objc_mutex_t __class_table_lock = NULL; | |
144 | ||
145 | /* CLASS_TABLE_HASH is how we compute the hash of a class name. It is | |
146 | a macro - *not* a function - arguments *are* modified directly. | |
147 | ||
148 | INDEX should be a variable holding an int; | |
149 | HASH should be a variable holding an int; | |
150 | CLASS_NAME should be a variable holding a (char *) to the class_name. | |
151 | ||
152 | After the macro is executed, INDEX contains the length of the | |
153 | string, and HASH the computed hash of the string; CLASS_NAME is | |
154 | untouched. */ | |
155 | ||
156 | #define CLASS_TABLE_HASH(INDEX, HASH, CLASS_NAME) \ | |
157 | HASH = 0; \ | |
158 | for (INDEX = 0; CLASS_NAME[INDEX] != '\0'; INDEX++) \ | |
159 | { \ | |
160 | HASH = (HASH << 4) ^ (HASH >> 28) ^ CLASS_NAME[INDEX]; \ | |
161 | } \ | |
162 | \ | |
163 | HASH = (HASH ^ (HASH >> 10) ^ (HASH >> 20)) & CLASS_TABLE_MASK; | |
164 | ||
165 | /* Setup the table. */ | |
166 | static void | |
8f8c44cb | 167 | class_table_setup (void) |
2726bdba NP |
168 | { |
169 | /* Start - nothing in the table. */ | |
40165636 | 170 | memset (class_table_array, 0, sizeof (class_node_ptr) * CLASS_TABLE_SIZE); |
2726bdba NP |
171 | |
172 | /* The table writing mutex. */ | |
173 | __class_table_lock = objc_mutex_allocate (); | |
174 | } | |
175 | ||
176 | ||
177 | /* Insert a class in the table (used when a new class is registered). */ | |
178 | static void | |
179 | class_table_insert (const char *class_name, Class class_pointer) | |
180 | { | |
181 | int hash, length; | |
182 | class_node_ptr new_node; | |
183 | ||
184 | /* Find out the class name's hash and length. */ | |
185 | CLASS_TABLE_HASH (length, hash, class_name); | |
186 | ||
187 | /* Prepare the new node holding the class. */ | |
188 | new_node = objc_malloc (sizeof (struct class_node)); | |
189 | new_node->name = class_name; | |
190 | new_node->length = length; | |
191 | new_node->pointer = class_pointer; | |
192 | ||
193 | /* Lock the table for modifications. */ | |
194 | objc_mutex_lock (__class_table_lock); | |
195 | ||
196 | /* Insert the new node in the table at the beginning of the table at | |
197 | class_table_array[hash]. */ | |
198 | new_node->next = class_table_array[hash]; | |
199 | class_table_array[hash] = new_node; | |
200 | ||
201 | objc_mutex_unlock (__class_table_lock); | |
202 | } | |
203 | ||
204 | /* Replace a class in the table (used only by poseAs:). */ | |
205 | static void | |
206 | class_table_replace (Class old_class_pointer, Class new_class_pointer) | |
207 | { | |
208 | int hash; | |
209 | class_node_ptr node; | |
210 | ||
211 | objc_mutex_lock (__class_table_lock); | |
212 | ||
213 | hash = 0; | |
214 | node = class_table_array[hash]; | |
215 | ||
216 | while (hash < CLASS_TABLE_SIZE) | |
217 | { | |
218 | if (node == NULL) | |
219 | { | |
220 | hash++; | |
221 | if (hash < CLASS_TABLE_SIZE) | |
222 | { | |
223 | node = class_table_array[hash]; | |
224 | } | |
225 | } | |
226 | else | |
227 | { | |
228 | Class class1 = node->pointer; | |
229 | ||
230 | if (class1 == old_class_pointer) | |
231 | { | |
232 | node->pointer = new_class_pointer; | |
233 | } | |
234 | node = node->next; | |
235 | } | |
236 | } | |
88e17b57 | 237 | |
2726bdba NP |
238 | objc_mutex_unlock (__class_table_lock); |
239 | } | |
240 | ||
241 | ||
242 | /* Get a class from the table. This does not need mutex protection. | |
243 | Currently, this function is called each time you call a static | |
244 | method, this is why it must be very fast. */ | |
245 | static inline Class | |
246 | class_table_get_safe (const char *class_name) | |
247 | { | |
248 | class_node_ptr node; | |
249 | int length, hash; | |
250 | ||
251 | /* Compute length and hash. */ | |
252 | CLASS_TABLE_HASH (length, hash, class_name); | |
253 | ||
254 | node = class_table_array[hash]; | |
255 | ||
256 | if (node != NULL) | |
257 | { | |
258 | do | |
259 | { | |
260 | if (node->length == length) | |
261 | { | |
262 | /* Compare the class names. */ | |
263 | int i; | |
264 | ||
265 | for (i = 0; i < length; i++) | |
266 | { | |
267 | if ((node->name)[i] != class_name[i]) | |
268 | { | |
269 | break; | |
270 | } | |
271 | } | |
272 | ||
273 | if (i == length) | |
274 | { | |
275 | /* They are equal! */ | |
276 | return node->pointer; | |
277 | } | |
278 | } | |
279 | } | |
280 | while ((node = node->next) != NULL); | |
281 | } | |
282 | ||
283 | return Nil; | |
284 | } | |
285 | ||
286 | /* Enumerate over the class table. */ | |
287 | struct class_table_enumerator | |
288 | { | |
289 | int hash; | |
290 | class_node_ptr node; | |
291 | }; | |
292 | ||
293 | ||
294 | static Class | |
295 | class_table_next (struct class_table_enumerator **e) | |
296 | { | |
297 | struct class_table_enumerator *enumerator = *e; | |
298 | class_node_ptr next; | |
299 | ||
300 | if (enumerator == NULL) | |
301 | { | |
302 | *e = objc_malloc (sizeof (struct class_table_enumerator)); | |
303 | enumerator = *e; | |
304 | enumerator->hash = 0; | |
305 | enumerator->node = NULL; | |
306 | ||
307 | next = class_table_array[enumerator->hash]; | |
308 | } | |
309 | else | |
310 | { | |
311 | next = enumerator->node->next; | |
312 | } | |
313 | ||
314 | if (next != NULL) | |
315 | { | |
316 | enumerator->node = next; | |
317 | return enumerator->node->pointer; | |
318 | } | |
319 | else | |
320 | { | |
321 | enumerator->hash++; | |
322 | ||
323 | while (enumerator->hash < CLASS_TABLE_SIZE) | |
324 | { | |
325 | next = class_table_array[enumerator->hash]; | |
326 | if (next != NULL) | |
327 | { | |
328 | enumerator->node = next; | |
329 | return enumerator->node->pointer; | |
330 | } | |
331 | enumerator->hash++; | |
332 | } | |
333 | ||
334 | /* Ok - table finished - done. */ | |
335 | objc_free (enumerator); | |
336 | return Nil; | |
337 | } | |
338 | } | |
339 | ||
340 | #if 0 /* DEBUGGING FUNCTIONS */ | |
341 | /* Debugging function - print the class table. */ | |
342 | void | |
40165636 | 343 | class_table_print (void) |
2726bdba NP |
344 | { |
345 | int i; | |
346 | ||
347 | for (i = 0; i < CLASS_TABLE_SIZE; i++) | |
348 | { | |
349 | class_node_ptr node; | |
350 | ||
351 | printf ("%d:\n", i); | |
352 | node = class_table_array[i]; | |
353 | ||
354 | while (node != NULL) | |
355 | { | |
356 | printf ("\t%s\n", node->name); | |
357 | node = node->next; | |
358 | } | |
359 | } | |
360 | } | |
361 | ||
362 | /* Debugging function - print an histogram of number of classes in | |
363 | function of hash key values. Useful to evaluate the hash function | |
364 | in real cases. */ | |
365 | void | |
40165636 | 366 | class_table_print_histogram (void) |
2726bdba NP |
367 | { |
368 | int i, j; | |
369 | int counter = 0; | |
370 | ||
371 | for (i = 0; i < CLASS_TABLE_SIZE; i++) | |
372 | { | |
373 | class_node_ptr node; | |
374 | ||
375 | node = class_table_array[i]; | |
376 | ||
377 | while (node != NULL) | |
378 | { | |
379 | counter++; | |
380 | node = node->next; | |
381 | } | |
382 | if (((i + 1) % 50) == 0) | |
383 | { | |
384 | printf ("%4d:", i + 1); | |
385 | for (j = 0; j < counter; j++) | |
386 | { | |
387 | printf ("X"); | |
388 | } | |
389 | printf ("\n"); | |
390 | counter = 0; | |
391 | } | |
392 | } | |
393 | printf ("%4d:", i + 1); | |
394 | for (j = 0; j < counter; j++) | |
395 | { | |
396 | printf ("X"); | |
397 | } | |
398 | printf ("\n"); | |
399 | } | |
400 | #endif /* DEBUGGING FUNCTIONS */ | |
401 | ||
402 | /** | |
403 | ** Objective-C runtime functions | |
404 | **/ | |
405 | ||
406 | /* From now on, the only access to the class table data structure | |
407 | should be via the class_table_* functions. */ | |
408 | ||
409 | /* This is a hook which is called by objc_get_class and | |
410 | objc_lookup_class if the runtime is not able to find the class. | |
411 | This may e.g. try to load in the class using dynamic loading. */ | |
40165636 | 412 | Class (*_objc_lookup_class) (const char *name) = 0; /* !T:SAFE */ |
88e17b57 BE |
413 | |
414 | ||
2726bdba | 415 | /* True when class links has been resolved. */ |
88e17b57 BE |
416 | BOOL __objc_class_links_resolved = NO; /* !T:UNUSED */ |
417 | ||
418 | ||
40165636 RB |
419 | void |
420 | __objc_init_class_tables (void) | |
88e17b57 | 421 | { |
2726bdba NP |
422 | /* Allocate the class hash table. */ |
423 | ||
40165636 | 424 | if (__class_table_lock) |
88e17b57 | 425 | return; |
2726bdba | 426 | |
40165636 | 427 | objc_mutex_lock (__objc_runtime_mutex); |
2726bdba NP |
428 | |
429 | class_table_setup (); | |
88e17b57 | 430 | |
40165636 | 431 | objc_mutex_unlock (__objc_runtime_mutex); |
88e17b57 BE |
432 | } |
433 | ||
2726bdba NP |
434 | /* This function adds a class to the class hash table, and assigns the |
435 | class a number, unless it's already known. */ | |
88e17b57 | 436 | void |
40165636 | 437 | __objc_add_class_to_hash (Class class) |
88e17b57 BE |
438 | { |
439 | Class h_class; | |
440 | ||
40165636 | 441 | objc_mutex_lock (__objc_runtime_mutex); |
88e17b57 | 442 | |
2726bdba | 443 | /* Make sure the table is there. */ |
40165636 | 444 | assert (__class_table_lock); |
88e17b57 | 445 | |
2726bdba | 446 | /* Make sure it's not a meta class. */ |
40165636 | 447 | assert (CLS_ISCLASS (class)); |
88e17b57 BE |
448 | |
449 | /* Check to see if the class is already in the hash table. */ | |
2726bdba | 450 | h_class = class_table_get_safe (class->name); |
40165636 | 451 | if (! h_class) |
88e17b57 BE |
452 | { |
453 | /* The class isn't in the hash table. Add the class and assign a class | |
454 | number. */ | |
455 | static unsigned int class_number = 1; | |
456 | ||
40165636 RB |
457 | CLS_SETNUMBER (class, class_number); |
458 | CLS_SETNUMBER (class->class_pointer, class_number); | |
88e17b57 BE |
459 | |
460 | ++class_number; | |
2726bdba | 461 | class_table_insert (class->name, class); |
88e17b57 BE |
462 | } |
463 | ||
40165636 | 464 | objc_mutex_unlock (__objc_runtime_mutex); |
88e17b57 BE |
465 | } |
466 | ||
467 | /* Get the class object for the class named NAME. If NAME does not | |
468 | identify a known class, the hook _objc_lookup_class is called. If | |
2726bdba | 469 | this fails, nil is returned. */ |
40165636 RB |
470 | Class |
471 | objc_lookup_class (const char *name) | |
88e17b57 BE |
472 | { |
473 | Class class; | |
474 | ||
2726bdba | 475 | class = class_table_get_safe (name); |
88e17b57 BE |
476 | |
477 | if (class) | |
478 | return class; | |
479 | ||
480 | if (_objc_lookup_class) | |
40165636 | 481 | return (*_objc_lookup_class) (name); |
88e17b57 BE |
482 | else |
483 | return 0; | |
484 | } | |
485 | ||
486 | /* Get the class object for the class named NAME. If NAME does not | |
487 | identify a known class, the hook _objc_lookup_class is called. If | |
2726bdba | 488 | this fails, an error message is issued and the system aborts. */ |
88e17b57 BE |
489 | Class |
490 | objc_get_class (const char *name) | |
491 | { | |
492 | Class class; | |
493 | ||
2726bdba | 494 | class = class_table_get_safe (name); |
88e17b57 BE |
495 | |
496 | if (class) | |
497 | return class; | |
498 | ||
499 | if (_objc_lookup_class) | |
40165636 | 500 | class = (*_objc_lookup_class) (name); |
88e17b57 | 501 | |
40165636 | 502 | if (class) |
88e17b57 BE |
503 | return class; |
504 | ||
40165636 RB |
505 | objc_error (nil, OBJC_ERR_BAD_CLASS, |
506 | "objc runtime: cannot find class %s\n", name); | |
88e17b57 BE |
507 | return 0; |
508 | } | |
509 | ||
510 | MetaClass | |
40165636 | 511 | objc_get_meta_class (const char *name) |
88e17b57 | 512 | { |
40165636 | 513 | return objc_get_class (name)->class_pointer; |
88e17b57 BE |
514 | } |
515 | ||
516 | /* This function provides a way to enumerate all the classes in the | |
517 | executable. Pass *ENUM_STATE == NULL to start the enumeration. The | |
518 | function will return 0 when there are no more classes. | |
519 | For example: | |
520 | id class; | |
521 | void *es = NULL; | |
40165636 | 522 | while ((class = objc_next_class (&es))) |
88e17b57 BE |
523 | ... do something with class; |
524 | */ | |
525 | Class | |
40165636 | 526 | objc_next_class (void **enum_state) |
88e17b57 | 527 | { |
2726bdba | 528 | Class class; |
88e17b57 | 529 | |
40165636 | 530 | objc_mutex_lock (__objc_runtime_mutex); |
2726bdba NP |
531 | |
532 | /* Make sure the table is there. */ | |
40165636 | 533 | assert (__class_table_lock); |
88e17b57 | 534 | |
40165636 | 535 | class = class_table_next ((struct class_table_enumerator **) enum_state); |
88e17b57 | 536 | |
40165636 | 537 | objc_mutex_unlock (__objc_runtime_mutex); |
2726bdba NP |
538 | |
539 | return class; | |
88e17b57 BE |
540 | } |
541 | ||
2726bdba NP |
542 | /* Resolve super/subclass links for all classes. The only thing we |
543 | can be sure of is that the class_pointer for class objects point to | |
544 | the right meta class objects. */ | |
40165636 RB |
545 | void |
546 | __objc_resolve_class_links (void) | |
88e17b57 | 547 | { |
2726bdba | 548 | struct class_table_enumerator *es = NULL; |
88e17b57 | 549 | Class object_class = objc_get_class ("Object"); |
2726bdba | 550 | Class class1; |
88e17b57 | 551 | |
40165636 | 552 | assert (object_class); |
88e17b57 | 553 | |
40165636 | 554 | objc_mutex_lock (__objc_runtime_mutex); |
88e17b57 | 555 | |
2726bdba NP |
556 | /* Assign subclass links. */ |
557 | while ((class1 = class_table_next (&es))) | |
88e17b57 | 558 | { |
88e17b57 | 559 | /* Make sure we have what we think we have. */ |
40165636 RB |
560 | assert (CLS_ISCLASS (class1)); |
561 | assert (CLS_ISMETA (class1->class_pointer)); | |
88e17b57 | 562 | |
2726bdba NP |
563 | /* The class_pointer of all meta classes point to Object's meta |
564 | class. */ | |
88e17b57 BE |
565 | class1->class_pointer->class_pointer = object_class->class_pointer; |
566 | ||
40165636 | 567 | if (! CLS_ISRESOLV (class1)) |
88e17b57 | 568 | { |
40165636 RB |
569 | CLS_SETRESOLV (class1); |
570 | CLS_SETRESOLV (class1->class_pointer); | |
88e17b57 | 571 | |
40165636 | 572 | if (class1->super_class) |
88e17b57 BE |
573 | { |
574 | Class a_super_class | |
575 | = objc_get_class ((char *) class1->super_class); | |
576 | ||
577 | assert (a_super_class); | |
578 | ||
579 | DEBUG_PRINTF ("making class connections for: %s\n", | |
580 | class1->name); | |
581 | ||
2726bdba | 582 | /* Assign subclass links for superclass. */ |
88e17b57 BE |
583 | class1->sibling_class = a_super_class->subclass_list; |
584 | a_super_class->subclass_list = class1; | |
585 | ||
2726bdba | 586 | /* Assign subclass links for meta class of superclass. */ |
88e17b57 BE |
587 | if (a_super_class->class_pointer) |
588 | { | |
589 | class1->class_pointer->sibling_class | |
590 | = a_super_class->class_pointer->subclass_list; | |
591 | a_super_class->class_pointer->subclass_list | |
592 | = class1->class_pointer; | |
593 | } | |
594 | } | |
2726bdba NP |
595 | else /* A root class, make its meta object be a subclass of |
596 | Object. */ | |
88e17b57 BE |
597 | { |
598 | class1->class_pointer->sibling_class | |
599 | = object_class->subclass_list; | |
600 | object_class->subclass_list = class1->class_pointer; | |
601 | } | |
602 | } | |
603 | } | |
604 | ||
2726bdba NP |
605 | /* Assign superclass links. */ |
606 | es = NULL; | |
607 | while ((class1 = class_table_next (&es))) | |
88e17b57 | 608 | { |
88e17b57 BE |
609 | Class sub_class; |
610 | for (sub_class = class1->subclass_list; sub_class; | |
611 | sub_class = sub_class->sibling_class) | |
612 | { | |
613 | sub_class->super_class = class1; | |
40165636 | 614 | if (CLS_ISCLASS (sub_class)) |
88e17b57 BE |
615 | sub_class->class_pointer->super_class = class1->class_pointer; |
616 | } | |
617 | } | |
618 | ||
40165636 | 619 | objc_mutex_unlock (__objc_runtime_mutex); |
88e17b57 BE |
620 | } |
621 | ||
622 | ||
623 | ||
624 | #define CLASSOF(c) ((c)->class_pointer) | |
625 | ||
626 | Class | |
627 | class_pose_as (Class impostor, Class super_class) | |
628 | { | |
40165636 | 629 | if (! CLS_ISRESOLV (impostor)) |
88e17b57 BE |
630 | __objc_resolve_class_links (); |
631 | ||
2726bdba | 632 | /* Preconditions */ |
88e17b57 BE |
633 | assert (impostor); |
634 | assert (super_class); | |
635 | assert (impostor->super_class == super_class); | |
636 | assert (CLS_ISCLASS (impostor)); | |
637 | assert (CLS_ISCLASS (super_class)); | |
638 | assert (impostor->instance_size == super_class->instance_size); | |
639 | ||
640 | { | |
641 | Class *subclass = &(super_class->subclass_list); | |
642 | ||
2726bdba | 643 | /* Move subclasses of super_class to impostor. */ |
88e17b57 BE |
644 | while (*subclass) |
645 | { | |
2726bdba NP |
646 | Class nextSub = (*subclass)->sibling_class; |
647 | ||
648 | if (*subclass != impostor) | |
649 | { | |
650 | Class sub = *subclass; | |
651 | ||
652 | /* Classes */ | |
653 | sub->sibling_class = impostor->subclass_list; | |
654 | sub->super_class = impostor; | |
655 | impostor->subclass_list = sub; | |
656 | ||
657 | /* It will happen that SUB is not a class object if it is | |
658 | the top of the meta class hierarchy chain (root | |
659 | meta-class objects inherit their class object). If | |
660 | that is the case... don't mess with the meta-meta | |
661 | class. */ | |
662 | if (CLS_ISCLASS (sub)) | |
663 | { | |
664 | /* Meta classes */ | |
665 | CLASSOF (sub)->sibling_class = | |
666 | CLASSOF (impostor)->subclass_list; | |
667 | CLASSOF (sub)->super_class = CLASSOF (impostor); | |
668 | CLASSOF (impostor)->subclass_list = CLASSOF (sub); | |
669 | } | |
670 | } | |
671 | ||
672 | *subclass = nextSub; | |
88e17b57 BE |
673 | } |
674 | ||
2726bdba | 675 | /* Set subclasses of superclass to be impostor only. */ |
88e17b57 BE |
676 | super_class->subclass_list = impostor; |
677 | CLASSOF (super_class)->subclass_list = CLASSOF (impostor); | |
678 | ||
2726bdba | 679 | /* Set impostor to have no sibling classes. */ |
88e17b57 BE |
680 | impostor->sibling_class = 0; |
681 | CLASSOF (impostor)->sibling_class = 0; | |
682 | } | |
683 | ||
2726bdba | 684 | /* Check relationship of impostor and super_class is kept. */ |
88e17b57 BE |
685 | assert (impostor->super_class == super_class); |
686 | assert (CLASSOF (impostor)->super_class == CLASSOF (super_class)); | |
687 | ||
2726bdba NP |
688 | /* This is how to update the lookup table. Regardless of what the |
689 | keys of the hashtable is, change all values that are superclass | |
690 | into impostor. */ | |
88e17b57 | 691 | |
40165636 | 692 | objc_mutex_lock (__objc_runtime_mutex); |
88e17b57 | 693 | |
2726bdba | 694 | class_table_replace (super_class, impostor); |
88e17b57 | 695 | |
40165636 | 696 | objc_mutex_unlock (__objc_runtime_mutex); |
88e17b57 | 697 | |
2726bdba | 698 | /* Next, we update the dispatch tables... */ |
88e17b57 BE |
699 | __objc_update_dispatch_table_for_class (CLASSOF (impostor)); |
700 | __objc_update_dispatch_table_for_class (impostor); | |
701 | ||
702 | return impostor; | |
703 | } |