libobjc/Protocol.m

/* This file contains the implementation of class Protocol.
   Copyright (C) 1993, 2004, 2009 Free Software Foundation, Inc.

This file is part of GCC. 

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC 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 General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */ 

#include "objc/Protocol.h"
#include "objc/objc-api.h"

/* Method description list */
struct objc_method_description_list {
        int count;
        struct objc_method_description list[1];
};


@implementation Protocol
{
@private
        char *protocol_name;
        struct objc_protocol_list *protocol_list;
        struct objc_method_description_list *instance_methods, *class_methods; 
}

/* Obtaining attributes intrinsic to the protocol */

- (const char *)name
{
  return protocol_name;
}

/* Testing protocol conformance */

- (BOOL) conformsTo: (Protocol *)aProtocolObject
{
  size_t i;
  struct objc_protocol_list* proto_list;

  if (aProtocolObject == nil)
    return NO;

  if (!strcmp(aProtocolObject->protocol_name, self->protocol_name))
    return YES;

  for (proto_list = protocol_list; proto_list; proto_list = proto_list->next)
    {
      for (i=0; i < proto_list->count; i++)
	{
	  if ([proto_list->list[i] conformsTo: aProtocolObject])
	    return YES;
	}
    }

  return NO;
}

/* Looking up information specific to a protocol */

- (struct objc_method_description *) descriptionForInstanceMethod:(SEL)aSel
{
  int i;
  struct objc_protocol_list* proto_list;
  const char* name = sel_get_name (aSel);
  struct objc_method_description *result;

  if (instance_methods)
    for (i = 0; i < instance_methods->count; i++)
      {
	if (!strcmp ((char*)instance_methods->list[i].name, name))
	  return &(instance_methods->list[i]);
      }

  for (proto_list = protocol_list; proto_list; proto_list = proto_list->next)
    {
      size_t j;
      for (j=0; j < proto_list->count; j++)
	{
	  if ((result = [proto_list->list[j]
			 descriptionForInstanceMethod: aSel]))
	    return result;
	}
    }

  return NULL;
}

- (struct objc_method_description *) descriptionForClassMethod:(SEL)aSel;
{
  int i;
  struct objc_protocol_list* proto_list;
  const char* name = sel_get_name (aSel);
  struct objc_method_description *result;

  if (class_methods)
    for (i = 0; i < class_methods->count; i++)
      {
	if (!strcmp ((char*)class_methods->list[i].name, name))
	  return &(class_methods->list[i]);
      }

  for (proto_list = protocol_list; proto_list; proto_list = proto_list->next)
    {
      size_t j;
      for (j=0; j < proto_list->count; j++)
	{
	  if ((result = [proto_list->list[j]
			 descriptionForClassMethod: aSel]))
	    return result;
	}
    }

  return NULL;
}

- (unsigned) hash
{
  /* Compute a hash of the protocol_name; use the same hash algorithm
   * that we use for class names; protocol names and class names are
   * somewhat similar types of string spaces.
   */
  int hash = 0, index;
  
  for (index = 0; protocol_name[index] != '\0'; index++)
    {
      hash = (hash << 4) ^ (hash >> 28) ^ protocol_name[index];
    }

  hash = (hash ^ (hash >> 10) ^ (hash >> 20));

  return hash;
}

/*
 * Equality between formal protocols is only formal (nothing to do
 * with actually checking the list of methods they have!).  Two formal
 * Protocols are equal if and only if they have the same name.
 *
 * Please note (for comparisons with other implementations) that
 * checking the names is equivalent to checking that Protocol A
 * conforms to Protocol B and Protocol B conforms to Protocol A,
 * because this happens iff they have the same name.  If they have
 * different names, A conforms to B if and only if A includes B, but
 * the situation where A includes B and B includes A is a circular
 * dependency between Protocols which is forbidden by the compiler, so
 * A conforms to B and B conforms to A with A and B having different
 * names is an impossible case.
 */
- (BOOL) isEqual: (id)obj
{
  if (obj == self)
    return YES;

  if ([obj isKindOf: [Protocol class]])
    {
      if (strcmp (protocol_name, ((Protocol *)obj)->protocol_name) == 0)
	return YES;
    }

  return NO;
}
@end