libobjc/class.c

   1 /* GNU Objective C Runtime class related functions
   2    Copyright (C) 1993, 1995, 1996, 1997 Free Software Foundation, Inc.
   3    Contributed by Kresten Krab Thorup and Dennis Glatting.
   4
   5 This file is part of GNU CC.
   6
   7 GNU CC is free software; you can redistribute it and/or modify it under the
   8 terms of the GNU General Public License as published by the Free Software
   9 Foundation; either version 2, or (at your option) any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13 FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
  14 details.
  15
  16 You should have received a copy of the GNU General Public License along with
  17 GNU CC; see the file COPYING.  If not, write to the Free Software
  18 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* As a special exception, if you link this library with files compiled with
  21    GCC to produce an executable, this does not cause the resulting executable
  22    to be covered by the GNU General Public License. This exception does not
  23    however invalidate any other reasons why the executable file might be
  24    covered by the GNU General Public License.  */
  25
  26 #include "runtime.h"            /* the kitchen sink */
  27 #include "sarray.h"
  28
  29 /* The table of classname->class.  Used for objc_lookup_class and friends */
  30 static cache_ptr __objc_class_hash = 0;                 /* !T:MUTEX */
  31
  32 /* This is a hook which is called by objc_get_class and
  33    objc_lookup_class if the runtime is not able to find the class.
  34    This may e.g. try to load in the class using dynamic loading */
  35 Class (*_objc_lookup_class)(const char* name) = 0;      /* !T:SAFE */
  36
  37
  38 /* True when class links has been resolved */
  39 BOOL __objc_class_links_resolved = NO;                  /* !T:UNUSED */
  40
  41
  42 /* Initial number of buckets size of class hash table. */
  43 #define CLASS_HASH_SIZE 32
  44
  45 void __objc_init_class_tables()
  46 {
  47   /* Allocate the class hash table */
  48
  49   if(__objc_class_hash)
  50     return;
  51
  52   objc_mutex_lock(__objc_runtime_mutex);
  53
  54   __objc_class_hash
  55     =  hash_new (CLASS_HASH_SIZE,
  56                  (hash_func_type) hash_string,
  57                  (compare_func_type) compare_strings);
  58
  59   objc_mutex_unlock(__objc_runtime_mutex);
  60 }
  61
  62 /* This function adds a class to the class hash table, and assigns the
  63    class a number, unless it's already known */
  64 void
  65 __objc_add_class_to_hash(Class class)
  66 {
  67   Class h_class;
  68
  69   objc_mutex_lock(__objc_runtime_mutex);
  70
  71   /* make sure the table is there */
  72   assert(__objc_class_hash);
  73
  74   /* make sure it's not a meta class */
  75   assert(CLS_ISCLASS(class));
  76
  77   /* Check to see if the class is already in the hash table.  */
  78   h_class = hash_value_for_key (__objc_class_hash, class->name);
  79   if (!h_class)
  80     {
  81       /* The class isn't in the hash table.  Add the class and assign a class
  82          number.  */
  83       static unsigned int class_number = 1;
  84
  85       CLS_SETNUMBER(class, class_number);
  86       CLS_SETNUMBER(class->class_pointer, class_number);
  87
  88       ++class_number;
  89       hash_add (&__objc_class_hash, class->name, class);
  90     }
  91
  92   objc_mutex_unlock(__objc_runtime_mutex);
  93 }
  94
  95 /* Get the class object for the class named NAME.  If NAME does not
  96    identify a known class, the hook _objc_lookup_class is called.  If
  97    this fails, nil is returned */
  98 Class objc_lookup_class (const char* name)
  99 {
 100   Class class;
 101
 102   objc_mutex_lock(__objc_runtime_mutex);
 103
 104   /* Make sure the class hash table exists.  */
 105   assert (__objc_class_hash);
 106
 107   class = hash_value_for_key (__objc_class_hash, name);
 108
 109   objc_mutex_unlock(__objc_runtime_mutex);
 110
 111   if (class)
 112     return class;
 113
 114   if (_objc_lookup_class)
 115     return (*_objc_lookup_class)(name);
 116   else
 117     return 0;
 118 }
 119
 120 /* Get the class object for the class named NAME.  If NAME does not
 121    identify a known class, the hook _objc_lookup_class is called.  If
 122    this fails,  an error message is issued and the system aborts */
 123 Class
 124 objc_get_class (const char *name)
 125 {
 126   Class class;
 127
 128   objc_mutex_lock(__objc_runtime_mutex);
 129
 130   /* Make sure the class hash table exists.  */
 131   assert (__objc_class_hash);
 132
 133   class = hash_value_for_key (__objc_class_hash, name);
 134
 135   objc_mutex_unlock(__objc_runtime_mutex);
 136
 137   if (class)
 138     return class;
 139
 140   if (_objc_lookup_class)
 141     class = (*_objc_lookup_class)(name);
 142
 143   if(class)
 144     return class;
 145
 146   objc_error(nil, OBJC_ERR_BAD_CLASS,
 147              "objc runtime: cannot find class %s\n", name);
 148   return 0;
 149 }
 150
 151 MetaClass
 152 objc_get_meta_class(const char *name)
 153 {
 154   return objc_get_class(name)->class_pointer;
 155 }
 156
 157 /* This function provides a way to enumerate all the classes in the
 158    executable.  Pass *ENUM_STATE == NULL to start the enumeration.  The
 159    function will return 0 when there are no more classes.
 160    For example:
 161        id class;
 162        void *es = NULL;
 163        while ((class = objc_next_class(&es)))
 164          ... do something with class;
 165 */
 166 Class
 167 objc_next_class(void **enum_state)
 168 {
 169   objc_mutex_lock(__objc_runtime_mutex);
 170
 171   /* make sure the table is there */
 172   assert(__objc_class_hash);
 173
 174   *(node_ptr*)enum_state =
 175     hash_next(__objc_class_hash, *(node_ptr*)enum_state);
 176
 177   objc_mutex_unlock(__objc_runtime_mutex);
 178
 179   if (*(node_ptr*)enum_state)
 180     return (*(node_ptr*)enum_state)->value;
 181   return (Class)0;
 182 }
 183
 184 /* Resolve super/subclass links for all classes.  The only thing we
 185    can be sure of is that the class_pointer for class objects point
 186    to the right meta class objects */
 187 void __objc_resolve_class_links()
 188 {
 189   node_ptr node;
 190   Class object_class = objc_get_class ("Object");
 191
 192   assert(object_class);
 193
 194   objc_mutex_lock(__objc_runtime_mutex);
 195
 196   /* Assign subclass links */
 197   for (node = hash_next (__objc_class_hash, NULL); node;
 198        node = hash_next (__objc_class_hash, node))
 199     {
 200       Class class1 = node->value;
 201
 202       /* Make sure we have what we think we have.  */
 203       assert (CLS_ISCLASS(class1));
 204       assert (CLS_ISMETA(class1->class_pointer));
 205
 206       /* The class_pointer of all meta classes point to Object's meta class. */
 207       class1->class_pointer->class_pointer = object_class->class_pointer;
 208
 209       if (!(CLS_ISRESOLV(class1)))
 210         {
 211           CLS_SETRESOLV(class1);
 212           CLS_SETRESOLV(class1->class_pointer);
 213
 214           if(class1->super_class)
 215             {
 216               Class a_super_class
 217                 = objc_get_class ((char *) class1->super_class);
 218
 219               assert (a_super_class);
 220
 221               DEBUG_PRINTF ("making class connections for: %s\n",
 222                             class1->name);
 223
 224               /* assign subclass links for superclass */
 225               class1->sibling_class = a_super_class->subclass_list;
 226               a_super_class->subclass_list = class1;
 227
 228               /* Assign subclass links for meta class of superclass */
 229               if (a_super_class->class_pointer)
 230                 {
 231                   class1->class_pointer->sibling_class
 232                     = a_super_class->class_pointer->subclass_list;
 233                   a_super_class->class_pointer->subclass_list
 234                     = class1->class_pointer;
 235                 }
 236             }
 237           else                  /* a root class, make its meta object */
 238                                 /* be a subclass of Object */
 239             {
 240               class1->class_pointer->sibling_class
 241                 = object_class->subclass_list;
 242               object_class->subclass_list = class1->class_pointer;
 243             }
 244         }
 245     }
 246
 247   /* Assign superclass links */
 248   for (node = hash_next (__objc_class_hash, NULL); node;
 249        node = hash_next (__objc_class_hash, node))
 250     {
 251       Class class1 = node->value;
 252       Class sub_class;
 253       for (sub_class = class1->subclass_list; sub_class;
 254            sub_class = sub_class->sibling_class)
 255         {
 256           sub_class->super_class = class1;
 257           if(CLS_ISCLASS(sub_class))
 258             sub_class->class_pointer->super_class = class1->class_pointer;
 259         }
 260     }
 261
 262   objc_mutex_unlock(__objc_runtime_mutex);
 263 }
 264
 265
 266
 267 #define CLASSOF(c) ((c)->class_pointer)
 268
 269 Class
 270 class_pose_as (Class impostor, Class super_class)
 271 {
 272   node_ptr node;
 273   Class class1;
 274
 275   if (!CLS_ISRESOLV (impostor))
 276     __objc_resolve_class_links ();
 277
 278   /* preconditions */
 279   assert (impostor);
 280   assert (super_class);
 281   assert (impostor->super_class == super_class);
 282   assert (CLS_ISCLASS (impostor));
 283   assert (CLS_ISCLASS (super_class));
 284   assert (impostor->instance_size == super_class->instance_size);
 285
 286   {
 287     Class *subclass = &(super_class->subclass_list);
 288
 289     /* move subclasses of super_class to impostor */
 290     while (*subclass)
 291       {
 292         Class nextSub = (*subclass)->sibling_class;
 293
 294         if (*subclass != impostor)
 295           {
 296             Class sub = *subclass;
 297
 298             /* classes */
 299             sub->sibling_class = impostor->subclass_list;
 300             sub->super_class = impostor;
 301             impostor->subclass_list = sub;
 302
 303             /* It will happen that SUB is not a class object if it is
 304                the top of the meta class hierarchy chain.  (root
 305                meta-class objects inherit their class object)  If that is
 306                the case... don't mess with the meta-meta class. */
 307             if (CLS_ISCLASS (sub))
 308               {
 309                 /* meta classes */
 310                 CLASSOF (sub)->sibling_class =
 311                   CLASSOF (impostor)->subclass_list;
 312                 CLASSOF (sub)->super_class = CLASSOF (impostor);
 313                 CLASSOF (impostor)->subclass_list = CLASSOF (sub);
 314               }
 315           }
 316
 317         *subclass = nextSub;
 318       }
 319
 320     /* set subclasses of superclass to be impostor only */
 321     super_class->subclass_list = impostor;
 322     CLASSOF (super_class)->subclass_list = CLASSOF (impostor);
 323
 324     /* set impostor to have no sibling classes */
 325     impostor->sibling_class = 0;
 326     CLASSOF (impostor)->sibling_class = 0;
 327   }
 328
 329   /* check relationship of impostor and super_class is kept. */
 330   assert (impostor->super_class == super_class);
 331   assert (CLASSOF (impostor)->super_class == CLASSOF (super_class));
 332
 333   /* This is how to update the lookup table. Regardless of
 334      what the keys of the hashtable is, change all values that are
 335      superclass into impostor. */
 336
 337   objc_mutex_lock(__objc_runtime_mutex);
 338
 339   for (node = hash_next (__objc_class_hash, NULL); node;
 340        node = hash_next (__objc_class_hash, node))
 341     {
 342       class1 = (Class)node->value;
 343       if (class1 == super_class)
 344         {
 345           node->value = impostor; /* change hash table value */
 346         }
 347     }
 348
 349   objc_mutex_unlock(__objc_runtime_mutex);
 350
 351   /* next, we update the dispatch tables... */
 352   __objc_update_dispatch_table_for_class (CLASSOF (impostor));
 353   __objc_update_dispatch_table_for_class (impostor);
 354
 355   return impostor;
 356 }
 357
 358