class.c

gcc的组件

      
      while (node != NULL)
        {
          printf ("\t%s\n", node->name);
          node = node->next;
        }
    }
}

/* Debugging function - print an histogram of number of classes in
   function of hash key values.  Useful to evaluate the hash function
   in real cases.  */
void
class_table_print_histogram (void)
{
  int i, j;
  int counter = 0;
  
  for (i = 0; i < CLASS_TABLE_SIZE; i++)
    {
      class_node_ptr node;
      
      node = class_table_array[i];
      
      while (node != NULL)
        {
          counter++;
          node = node->next;
        }
      if (((i + 1) % 50) == 0)
        {
          printf ("%4d:", i + 1);
          for (j = 0; j < counter; j++)
            {
              printf ("X");
            }
          printf ("\n");
          counter = 0;
        }
    }
  printf ("%4d:", i + 1);
  for (j = 0; j < counter; j++)
    {
      printf ("X");
    }
  printf ("\n");
}
#endif /* DEBUGGING FUNCTIONS */

/**
 ** Objective-C runtime functions
 **/

/* From now on, the only access to the class table data structure
   should be via the class_table_* functions.  */

/* This is a hook which is called by objc_get_class and
   objc_lookup_class if the runtime is not able to find the class.  
   This may e.g. try to load in the class using dynamic loading.  */
Class (*_objc_lookup_class) (const char *name) = 0;      /* !T:SAFE */


/* True when class links has been resolved.  */     
BOOL __objc_class_links_resolved = NO;                  /* !T:UNUSED */


void
__objc_init_class_tables (void)
{
  /* Allocate the class hash table.  */
  
  if (__class_table_lock)
    return;
  
  objc_mutex_lock (__objc_runtime_mutex);
  
  class_table_setup ();

  objc_mutex_unlock (__objc_runtime_mutex);
}  

/* This function adds a class to the class hash table, and assigns the
   class a number, unless it's already known.  */
void
__objc_add_class_to_hash (Class class)
{
  Class h_class;

  objc_mutex_lock (__objc_runtime_mutex);

  /* Make sure the table is there.  */
  assert (__class_table_lock);

  /* Make sure it's not a meta class.  */
  assert (CLS_ISCLASS (class));

  /* Check to see if the class is already in the hash table.  */
  h_class = class_table_get_safe (class->name);
  if (! h_class)
    {
      /* The class isn't in the hash table.  Add the class and assign a class
         number.  */
      static unsigned int class_number = 1;

      CLS_SETNUMBER (class, class_number);
      CLS_SETNUMBER (class->class_pointer, class_number);

      ++class_number;
      class_table_insert (class->name, class);
    }

  objc_mutex_unlock (__objc_runtime_mutex);
}

/* Get the class object for the class named NAME.  If NAME does not
   identify a known class, the hook _objc_lookup_class is called.  If
   this fails, nil is returned.  */
Class
objc_lookup_class (const char *name)
{
  Class class;

  class = class_table_get_safe (name);

  if (class)
    return class;

  if (_objc_lookup_class)
    return (*_objc_lookup_class) (name);
  else
    return 0;
}

/* Get the class object for the class named NAME.  If NAME does not
   identify a known class, the hook _objc_lookup_class is called.  If
   this fails, an error message is issued and the system aborts.  */
Class
objc_get_class (const char *name)
{
  Class class;

  class = class_table_get_safe (name);

  if (class)
    return class;

  if (_objc_lookup_class)
    class = (*_objc_lookup_class) (name);

  if (class)
    return class;
  
  objc_error (nil, OBJC_ERR_BAD_CLASS, 
              "objc runtime: cannot find class %s\n", name);
  return 0;
}

MetaClass
objc_get_meta_class (const char *name)
{
  return objc_get_class (name)->class_pointer;
}

/* This function provides a way to enumerate all the classes in the
   executable.  Pass *ENUM_STATE == NULL to start the enumeration.  The
   function will return 0 when there are no more classes.  
   For example: 
       id class; 
       void *es = NULL;
       while ((class = objc_next_class (&es)))
         ... do something with class; 
*/
Class
objc_next_class (void **enum_state)
{
  Class class;

  objc_mutex_lock (__objc_runtime_mutex);
  
  /* Make sure the table is there.  */
  assert (__class_table_lock);

  class = class_table_next ((struct class_table_enumerator **) enum_state);

  objc_mutex_unlock (__objc_runtime_mutex);
  
  return class;
}

/* Resolve super/subclass links for all classes.  The only thing we
   can be sure of is that the class_pointer for class objects point to
   the right meta class objects.  */
void
__objc_resolve_class_links (void)
{
  struct class_table_enumerator *es = NULL;
  Class object_class = objc_get_class ("Object");
  Class class1;

  assert (object_class);

  objc_mutex_lock (__objc_runtime_mutex);

  /* Assign subclass links.  */
  while ((class1 = class_table_next (&es)))
    {
      /* Make sure we have what we think we have.  */
      assert (CLS_ISCLASS (class1));
      assert (CLS_ISMETA (class1->class_pointer));

      /* The class_pointer of all meta classes point to Object's meta
         class.  */
      class1->class_pointer->class_pointer = object_class->class_pointer;

      if (! CLS_ISRESOLV (class1))
        {
          CLS_SETRESOLV (class1);
          CLS_SETRESOLV (class1->class_pointer);
              
          if (class1->super_class)
            {   
              Class a_super_class 
                = objc_get_class ((char *) class1->super_class);
              
              assert (a_super_class);
              
              DEBUG_PRINTF ("making class connections for: %s\n",
                            class1->name);
              
              /* Assign subclass links for superclass.  */
              class1->sibling_class = a_super_class->subclass_list;
              a_super_class->subclass_list = class1;
              
              /* Assign subclass links for meta class of superclass.  */
              if (a_super_class->class_pointer)
                {
                  class1->class_pointer->sibling_class
                    = a_super_class->class_pointer->subclass_list;
                  a_super_class->class_pointer->subclass_list 
                    = class1->class_pointer;
                }
            }
          else /* A root class, make its meta object be a subclass of
                  Object.  */
            {
              class1->class_pointer->sibling_class 
                = object_class->subclass_list;
              object_class->subclass_list = class1->class_pointer;
            }
        }
    }

  /* Assign superclass links.  */
   es = NULL;
   while ((class1 = class_table_next (&es)))
    {
      Class sub_class;
      for (sub_class = class1->subclass_list; sub_class;
           sub_class = sub_class->sibling_class)
        {
          sub_class->super_class = class1;
          if (CLS_ISCLASS (sub_class))
            sub_class->class_pointer->super_class = class1->class_pointer;
        }
    }

  objc_mutex_unlock (__objc_runtime_mutex);
}



#define CLASSOF(c) ((c)->class_pointer)

Class
class_pose_as (Class impostor, Class super_class)
{
  if (! CLS_ISRESOLV (impostor))
    __objc_resolve_class_links ();

  /* Preconditions */
  assert (impostor);
  assert (super_class);
  assert (impostor->super_class == super_class);
  assert (CLS_ISCLASS (impostor));
  assert (CLS_ISCLASS (super_class));
  assert (impostor->instance_size == super_class->instance_size);

  {
    Class *subclass = &(super_class->subclass_list);

    /* Move subclasses of super_class to impostor.  */
    while (*subclass)
      {
        Class nextSub = (*subclass)->sibling_class;

        if (*subclass != impostor)
          {
            Class sub = *subclass;

            /* Classes */
            sub->sibling_class = impostor->subclass_list;
            sub->super_class = impostor;
            impostor->subclass_list = sub;

            /* It will happen that SUB is not a class object if it is
               the top of the meta class hierarchy chain (root
               meta-class objects inherit their class object).  If
               that is the case... don't mess with the meta-meta
               class.  */
            if (CLS_ISCLASS (sub))
              {
                /* Meta classes */
                CLASSOF (sub)->sibling_class = 
                  CLASSOF (impostor)->subclass_list;
                CLASSOF (sub)->super_class = CLASSOF (impostor);
                CLASSOF (impostor)->subclass_list = CLASSOF (sub);
              }
          }

        *subclass = nextSub;
      }

    /* Set subclasses of superclass to be impostor only.  */
    super_class->subclass_list = impostor;
    CLASSOF (super_class)->subclass_list = CLASSOF (impostor);
    
    /* Set impostor to have no sibling classes.  */
    impostor->sibling_class = 0;
    CLASSOF (impostor)->sibling_class = 0;
  }
  
  /* Check relationship of impostor and super_class is kept.  */
  assert (impostor->super_class == super_class);
  assert (CLASSOF (impostor)->super_class == CLASSOF (super_class));

  /* This is how to update the lookup table.  Regardless of what the
     keys of the hashtable is, change all values that are superclass
     into impostor.  */

  objc_mutex_lock (__objc_runtime_mutex);

  class_table_replace (super_class, impostor);

  objc_mutex_unlock (__objc_runtime_mutex);

  /* Next, we update the dispatch tables...  */
  __objc_update_dispatch_table_for_class (CLASSOF (impostor));
  __objc_update_dispatch_table_for_class (impostor);

  return impostor;
}