libs-base/Source/behavior.m

/* Behaviors for Objective-C, "for Protocols with implementations".
   Copyright (C) 1995 Free Software Foundation, Inc.

   Written by:  R. Andrew McCallum <mccallum@gnu.ai.mit.edu>
   Date: March 1995

   This file is part of the GNU Objective C Class Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/ 

/* A Behavior can be seen as a "Protocol with an implementation" or a
   "Class without any instance variables".  A key feature of behaviors
   is that they give a degree of multiple inheritance.

   xxx not necessarily on the "no instance vars".  The behavior just has 
   to have the same layout as the class.

   The following function is a sneaky hack way that provides Behaviors
   without adding any new syntax to the Objective C language.  Simply
   define a class with the methods you want in the behavior, then call
   this function with that class as the BEHAVIOR argument.

   This function should be called in CLASS's +initialize method.

   If you add several behaviors to a class, be aware that the order of 
   the additions is significant.

   */

#include <objc/objc.h>
#include <objc/objc-api.h>
#include <objc/sarray.h>
#include <objects/objc-malloc.h>
#include <assert.h>

static int behavior_debug = 0;

static Method_t search_for_method_in_list (MethodList_t list, SEL op);
static void __objc_send_initialize(Class class);
#if 0
static void __objc_init_protocols (struct objc_protocol_list* protos);
static void __objc_class_add_protocols (Class class,
                                        struct objc_protocol_list* protos);
#endif
static BOOL class_is_kind_of(Class self, Class class);
void class_add_methods_if_not_there(Class class, MethodList_t mlist);

/* xxx consider using sendmsg.c:__objc_update_dispatch_table_for_class,
   but, I think it will be slower than the current method. */

void
set_behavior_debug(int i)
{
  behavior_debug = i;
}

void
class_add_behavior (Class class, Class behavior)
{
  Class behavior_super_class = class_get_super_class(behavior);

  assert(CLS_ISCLASS(class));
  assert(CLS_ISCLASS(behavior));

  __objc_send_initialize(class);
  __objc_send_initialize(behavior);

#if 0
  /* xxx Do protocols */
  if (behavior->protocols)
    {
      /* xxx Make sure they are not already there before adding. */
      __objc_init_protocols (behavior->protocols);
      __objc_class_add_protocols (class, behavior->protocols);
    }
#endif

  /* Add instance methods */
  class_add_methods_if_not_there(class, 
				behavior->methods);

  /* Add class methods */
  class_add_methods_if_not_there(class->class_pointer, 
				behavior->class_pointer->methods);

  /* Add behavior's superclass, if not already there. */
  {
    if (!class_is_kind_of(class, behavior_super_class))
      class_add_behavior(class, behavior_super_class);
  }

  return;
}

void
class_add_methods_if_not_there(Class class, MethodList_t mlist)
{
  static SEL initialize_sel = 0;

  if (!initialize_sel)
    initialize_sel = sel_register_name ("initialize");

  /* Add methods to class->dtable and class->methods */
  for ( ; mlist; mlist = mlist->method_next)
    {
      int counter;
      MethodList_t new_list;

      counter = mlist->method_count - 1;

      /* xxx This is a little wasteful of memory, since not necessarily 
	 all methods will go in here. */
      new_list = (MethodList_t)
	(*objc_malloc)
	  (sizeof(MethodList) + sizeof(struct objc_method[counter]));
      new_list->method_count = 0;

      while (counter >= 0)
        {
          Method_t method = &(mlist->method_list[counter]);

	  if (behavior_debug)
	    fprintf(stderr, "processing method %s\n", 
		    sel_get_name(method->method_name));

	  if (!search_for_method_in_list(class->methods, method->method_name)
	      && method->method_name->sel_id != initialize_sel->sel_id)
	    {
	      /* As long as the method isn't defined in the CLASS,
		 put the BEHAVIOR method in there.  Thus, behavior
		 methods override the superclasses' methods. */
	      sarray_at_put_safe (class->dtable,
				  (sidx) method->method_name->sel_id,
				  method->method_imp);
	      new_list->method_list[new_list->method_count] = *method;
	      (new_list->method_count)++;
	      if (behavior_debug)
		fprintf(stderr, "added method %s\n", 
			sel_get_name(method->method_name));
	    }
          counter -= 1;
        }
      new_list->method_next = class->methods;
      class->methods = new_list;
    }
}

#if 0
/* This is like class_add_method_list(), except is doesn't balk at 
   duplicates; it simply ignores them.  Thus, a method implemented 
   in CLASS overrides a method implemented in BEHAVIOR. */

void
class_add_behavior_method_list (Class class, MethodList_t list)
{
  int i;
  static SEL initialize_sel = 0;
  if (!initialize_sel)
    initialize_sel = sel_register_name ("initialize");

  /* Passing of a linked list is not allowed.  Do multiple calls.  */
  assert (!list->method_next);

  /* Check for duplicates.  */
  for (i = 0; i < list->method_count; ++i)
    {
      Method_t method = &list->method_list[i];

      if (method->method_name)  /* Sometimes these are NULL */
	{
	  if (search_for_method_in_list (class->methods, method->method_name)
	      && method->method_name->sel_id != initialize_sel->sel_id)
	    {
	      /* Duplication. Print a error message an change the method name
		 to NULL. */
	      fprintf (stderr, "attempt to add a existing method: %s\n",
		       sel_get_name(method->method_name));
	      method->method_name = 0;
	    }
	  else
	    {
	      /* Behavior method not implemented in class.  Add it. */
	      sarray_at_put_safe (class->dtable,
				  (sidx) method->method_name->sel_id,
				  method->method_imp);
	    }
	}
    }

  /* Add the methods to the class's method list.  */
  list->method_next = class->methods;
  class->methods = list;
}
#endif

/* Given a linked list of method and a method's name.  Search for the named
   method's method structure.  Return a pointer to the method's method
   structure if found.  NULL otherwise. */
static Method_t
search_for_method_in_list (MethodList_t list, SEL op)
{
  MethodList_t method_list = list;

  if (! sel_is_mapped (op))
    return NULL;

  /* If not found then we'll search the list.  */
  while (method_list)
    {
      int i;

      /* Search the method list.  */
      for (i = 0; i < method_list->method_count; ++i)
        {
          Method_t method = &method_list->method_list[i];

          if (method->method_name)
            if (method->method_name->sel_id == op->sel_id)
              return method;
        }

      /* The method wasn't found.  Follow the link to the next list of
         methods.  */
      method_list = method_list->method_next;
    }

  return NULL;
}

/* Send +initialize to class if not already done */
static void __objc_send_initialize(Class class)
{
  /* This *must* be a class object */
  assert(CLS_ISCLASS(class));
  assert(!CLS_ISMETA(class));

  if (!CLS_ISINITIALIZED(class))
    {
      CLS_SETINITIALIZED(class);
      CLS_SETINITIALIZED(class->class_pointer);

      if(class->super_class)
        __objc_send_initialize(class->super_class);

      {
        MethodList_t method_list = class->class_pointer->methods;
        SEL op = sel_register_name ("initialize");

        /* If not found then we'll search the list.  */
        while (method_list)
          {
            int i;

            /* Search the method list.  */
            for (i = 0; i < method_list->method_count; ++i)
              {
                Method_t method = &method_list->method_list[i];


                if (method->method_name->sel_id == op->sel_id)
                  (*method->method_imp)((id) class, op);
              }

            /* The method wasn't found.  Follow the link to the next list of
               methods.  */
            method_list = method_list->method_next;
          }
      }
    }
}

#if 0
static void
__objc_init_protocols (struct objc_protocol_list* protos)
{
  int i;
  static Class proto_class = 0;

  if (! protos)
    return;

  if (!proto_class)
    proto_class = objc_lookup_class("Protocol");

  if (!proto_class)
    {
      unclaimed_proto_list = list_cons (protos, unclaimed_proto_list);
      return;
    }

#if 0
  assert (protos->next == 0);   /* only single ones allowed */
#endif

  for(i = 0; i < protos->count; i++)
    {
      struct objc_protocol* aProto = protos->list[i];
      if (((size_t)aProto->class_pointer) == PROTOCOL_VERSION)
        {
          /* assign class pointer */
          aProto->class_pointer = proto_class;

          /* init super protocols */
          __objc_init_protocols (aProto->protocol_list);
        }
      else if (protos->list[i]->class_pointer != proto_class)
        {
          fprintf (stderr,
                   "Version %d doesn't match runtime protocol version %d\n",
                   (int)((char*)protos->list[i]->class_pointer-(char*)0),
                   PROTOCOL_VERSION);
          abort ();
        }
    }
}

static void __objc_class_add_protocols (Class class,
                                        struct objc_protocol_list* protos)
{
  /* Well... */
  if (! protos)
    return;

  /* Add it... */
  protos->next = class->protocols;
  class->protocols = protos;
}
#endif /* 0 */

static BOOL class_is_kind_of(Class self, Class aClassObject)
{
  Class class;

  for (class = self; class!=Nil; class = class_get_super_class(class))
    if (class==aClassObject)
      return YES;
  return NO;
}