runtime/objc-loadmethod.mm

   1 /*
   2  * Copyright (c) 2004-2006 Apple Inc.  All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 /***********************************************************************
  25 * objc-loadmethod.m
  26 * Support for +load methods.
  27 **********************************************************************/
  28
  29 #include "objc-loadmethod.h"
  30 #include "objc-private.h"
  31
  32 typedef void(*load_method_t)(id, SEL);
  33
  34 struct loadable_class {
  35     Class cls;  // may be NULL
  36     IMP method;
  37 };
  38
  39 struct loadable_category {
  40     Category cat;  // may be NULL
  41     IMP method;
  42 };
  43
  44
  45 // List of classes that need +load called (pending superclass +load)
  46 // This list always has superclasses first because of the way it is constructed
  47 static struct loadable_class *loadable_classes = NULL;
  48 static int loadable_classes_used = 0;
  49 static int loadable_classes_allocated = 0;
  50
  51 // List of categories that need +load called (pending parent class +load)
  52 static struct loadable_category *loadable_categories = NULL;
  53 static int loadable_categories_used = 0;
  54 static int loadable_categories_allocated = 0;
  55
  56
  57 /***********************************************************************
  58 * add_class_to_loadable_list
  59 * Class cls has just become connected. Schedule it for +load if
  60 * it implements a +load method.
  61 **********************************************************************/
  62 void add_class_to_loadable_list(Class cls)
  63 {
  64     IMP method;
  65
  66     recursive_mutex_assert_locked(&loadMethodLock);
  67
  68     method = _class_getLoadMethod(cls);
  69     if (!method) return;  // Don't bother if cls has no +load method
  70
  71     if (PrintLoading) {
  72         _objc_inform("LOAD: class '%s' scheduled for +load", _class_getName(cls));
  73     }
  74
  75     if (loadable_classes_used == loadable_classes_allocated) {
  76         loadable_classes_allocated = loadable_classes_allocated*2 + 16;
  77         loadable_classes = (struct loadable_class *)
  78             _realloc_internal(loadable_classes,
  79                               loadable_classes_allocated *
  80                               sizeof(struct loadable_class));
  81     }
  82
  83     loadable_classes[loadable_classes_used].cls = cls;
  84     loadable_classes[loadable_classes_used].method = method;
  85     loadable_classes_used++;
  86 }
  87
  88
  89 /***********************************************************************
  90 * add_category_to_loadable_list
  91 * Category cat's parent class exists and the category has been attached
  92 * to its class. Schedule this category for +load after its parent class
  93 * becomes connected and has its own +load method called.
  94 **********************************************************************/
  95 void add_category_to_loadable_list(Category cat)
  96 {
  97     IMP method;
  98
  99     recursive_mutex_assert_locked(&loadMethodLock);
 100
 101     method = _category_getLoadMethod(cat);
 102
 103     // Don't bother if cat has no +load method
 104     if (!method) return;
 105
 106     if (PrintLoading) {
 107         _objc_inform("LOAD: category '%s(%s)' scheduled for +load",
 108                      _category_getClassName(cat), _category_getName(cat));
 109     }
 110
 111     if (loadable_categories_used == loadable_categories_allocated) {
 112         loadable_categories_allocated = loadable_categories_allocated*2 + 16;
 113         loadable_categories = (struct loadable_category *)
 114             _realloc_internal(loadable_categories,
 115                               loadable_categories_allocated *
 116                               sizeof(struct loadable_category));
 117     }
 118
 119     loadable_categories[loadable_categories_used].cat = cat;
 120     loadable_categories[loadable_categories_used].method = method;
 121     loadable_categories_used++;
 122 }
 123
 124
 125 /***********************************************************************
 126 * remove_class_from_loadable_list
 127 * Class cls may have been loadable before, but it is now no longer
 128 * loadable (because its image is being unmapped).
 129 **********************************************************************/
 130 void remove_class_from_loadable_list(Class cls)
 131 {
 132     recursive_mutex_assert_locked(&loadMethodLock);
 133
 134     if (loadable_classes) {
 135         int i;
 136         for (i = 0; i < loadable_classes_used; i++) {
 137             if (loadable_classes[i].cls == cls) {
 138                 loadable_classes[i].cls = NULL;
 139                 if (PrintLoading) {
 140                     _objc_inform("LOAD: class '%s' unscheduled for +load", _class_getName(cls));
 141                 }
 142                 return;
 143             }
 144         }
 145     }
 146 }
 147
 148
 149 /***********************************************************************
 150 * remove_category_from_loadable_list
 151 * Category cat may have been loadable before, but it is now no longer
 152 * loadable (because its image is being unmapped).
 153 **********************************************************************/
 154 void remove_category_from_loadable_list(Category cat)
 155 {
 156     recursive_mutex_assert_locked(&loadMethodLock);
 157
 158     if (loadable_categories) {
 159         int i;
 160         for (i = 0; i < loadable_categories_used; i++) {
 161             if (loadable_categories[i].cat == cat) {
 162                 loadable_categories[i].cat = NULL;
 163                 if (PrintLoading) {
 164                     _objc_inform("LOAD: category '%s(%s)' unscheduled for +load",
 165                                  _category_getClassName(cat),
 166                                  _category_getName(cat));
 167                 }
 168                 return;
 169             }
 170         }
 171     }
 172 }
 173
 174
 175 /***********************************************************************
 176 * call_class_loads
 177 * Call all pending class +load methods.
 178 * If new classes become loadable, +load is NOT called for them.
 179 *
 180 * Called only by call_load_methods().
 181 **********************************************************************/
 182 static void call_class_loads(void)
 183 {
 184     int i;
 185
 186     // Detach current loadable list.
 187     struct loadable_class *classes = loadable_classes;
 188     int used = loadable_classes_used;
 189     loadable_classes = NULL;
 190     loadable_classes_allocated = 0;
 191     loadable_classes_used = 0;
 192
 193     // Call all +loads for the detached list.
 194     for (i = 0; i < used; i++) {
 195         Class cls = classes[i].cls;
 196         load_method_t load_method = (load_method_t)classes[i].method;
 197         if (!cls) continue;
 198
 199         if (PrintLoading) {
 200             _objc_inform("LOAD: +[%s load]\n", _class_getName(cls));
 201         }
 202         (*load_method)(cls, SEL_load);
 203     }
 204
 205     // Destroy the detached list.
 206     if (classes) _free_internal(classes);
 207 }
 208
 209
 210 /***********************************************************************
 211 * call_category_loads
 212 * Call some pending category +load methods.
 213 * The parent class of the +load-implementing categories has all of
 214 *   its categories attached, in case some are lazily waiting for +initalize.
 215 * Don't call +load unless the parent class is connected.
 216 * If new categories become loadable, +load is NOT called, and they
 217 *   are added to the end of the loadable list, and we return TRUE.
 218 * Return FALSE if no new categories became loadable.
 219 *
 220 * Called only by call_load_methods().
 221 **********************************************************************/
 222 static BOOL call_category_loads(void)
 223 {
 224     int i, shift;
 225     BOOL new_categories_added = NO;
 226
 227     // Detach current loadable list.
 228     struct loadable_category *cats = loadable_categories;
 229     int used = loadable_categories_used;
 230     int allocated = loadable_categories_allocated;
 231     loadable_categories = NULL;
 232     loadable_categories_allocated = 0;
 233     loadable_categories_used = 0;
 234
 235     // Call all +loads for the detached list.
 236     for (i = 0; i < used; i++) {
 237         Category cat = cats[i].cat;
 238         load_method_t load_method = (load_method_t)cats[i].method;
 239         Class cls;
 240         if (!cat) continue;
 241
 242         cls = _category_getClass(cat);
 243         if (cls  &&  _class_isLoadable(cls)) {
 244             if (PrintLoading) {
 245                 _objc_inform("LOAD: +[%s(%s) load]\n",
 246                              _class_getName(cls),
 247                              _category_getName(cat));
 248             }
 249             (*load_method)(cls, SEL_load);
 250             cats[i].cat = NULL;
 251         }
 252     }
 253
 254     // Compact detached list (order-preserving)
 255     shift = 0;
 256     for (i = 0; i < used; i++) {
 257         if (cats[i].cat) {
 258             cats[i-shift] = cats[i];
 259         } else {
 260             shift++;
 261         }
 262     }
 263     used -= shift;
 264
 265     // Copy any new +load candidates from the new list to the detached list.
 266     new_categories_added = (loadable_categories_used > 0);
 267     for (i = 0; i < loadable_categories_used; i++) {
 268         if (used == allocated) {
 269             allocated = allocated*2 + 16;
 270             cats = (struct loadable_category *)
 271                 _realloc_internal(cats, allocated *
 272                                   sizeof(struct loadable_category));
 273         }
 274         cats[used++] = loadable_categories[i];
 275     }
 276
 277     // Destroy the new list.
 278     if (loadable_categories) _free_internal(loadable_categories);
 279
 280     // Reattach the (now augmented) detached list.
 281     // But if there's nothing left to load, destroy the list.
 282     if (used) {
 283         loadable_categories = cats;
 284         loadable_categories_used = used;
 285         loadable_categories_allocated = allocated;
 286     } else {
 287         if (cats) _free_internal(cats);
 288         loadable_categories = NULL;
 289         loadable_categories_used = 0;
 290         loadable_categories_allocated = 0;
 291     }
 292
 293     if (PrintLoading) {
 294         if (loadable_categories_used != 0) {
 295             _objc_inform("LOAD: %d categories still waiting for +load\n",
 296                          loadable_categories_used);
 297         }
 298     }
 299
 300     return new_categories_added;
 301 }
 302
 303
 304 /***********************************************************************
 305 * call_load_methods
 306 * Call all pending class and category +load methods.
 307 * Class +load methods are called superclass-first.
 308 * Category +load methods are not called until after the parent class's +load.
 309 *
 310 * This method must be RE-ENTRANT, because a +load could trigger
 311 * more image mapping. In addition, the superclass-first ordering
 312 * must be preserved in the face of re-entrant calls. Therefore,
 313 * only the OUTERMOST call of this function will do anything, and
 314 * that call will handle all loadable classes, even those generated
 315 * while it was running.
 316 *
 317 * The sequence below preserves +load ordering in the face of
 318 * image loading during a +load, and make sure that no
 319 * +load method is forgotten because it was added during
 320 * a +load call.
 321 * Sequence:
 322 * 1. Repeatedly call class +loads until there aren't any more
 323 * 2. Call category +loads ONCE.
 324 * 3. Run more +loads if:
 325 *    (a) there are more classes to load, OR
 326 *    (b) there are some potential category +loads that have
 327 *        still never been attempted.
 328 * Category +loads are only run once to ensure "parent class first"
 329 * ordering, even if a category +load triggers a new loadable class
 330 * and a new loadable category attached to that class.
 331 *
 332 * Locking: loadMethodLock must be held by the caller
 333 *   All other locks must not be held.
 334 **********************************************************************/
 335 void call_load_methods(void)
 336 {
 337     static BOOL loading = NO;
 338     BOOL more_categories;
 339
 340     recursive_mutex_assert_locked(&loadMethodLock);
 341
 342     // Re-entrant calls do nothing; the outermost call will finish the job.
 343     if (loading) return;
 344     loading = YES;
 345
 346     void *pool = objc_autoreleasePoolPush();
 347
 348     do {
 349         // 1. Repeatedly call class +loads until there aren't any more
 350         while (loadable_classes_used > 0) {
 351             call_class_loads();
 352         }
 353
 354         // 2. Call category +loads ONCE
 355         more_categories = call_category_loads();
 356
 357         // 3. Run more +loads if there are classes OR more untried categories
 358     } while (loadable_classes_used > 0  ||  more_categories);
 359
 360     objc_autoreleasePoolPop(pool);
 361
 362     loading = NO;
 363 }
 364
 365