libobjc/Protocol.m

   1 /* This file contains the implementation of class Protocol.
   2    Copyright (C) 1993, 2004 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  19 Boston, MA 02110-1301, USA.  */
  20
  21 /* As a special exception, if you link this library with files
  22    compiled with GCC to produce an executable, this does not cause
  23    the resulting executable to be covered by the GNU General Public License.
  24    This exception does not however invalidate any other reasons why
  25    the executable file might be covered by the GNU General Public License.  */
  26
  27 #include "objc/Protocol.h"
  28 #include "objc/objc-api.h"
  29
  30 /* Method description list */
  31 struct objc_method_description_list {
  32         int count;
  33         struct objc_method_description list[1];
  34 };
  35
  36
  37 @implementation Protocol
  38 {
  39 @private
  40         char *protocol_name;
  41         struct objc_protocol_list *protocol_list;
  42         struct objc_method_description_list *instance_methods, *class_methods;
  43 }
  44
  45 /* Obtaining attributes intrinsic to the protocol */
  46
  47 - (const char *)name
  48 {
  49   return protocol_name;
  50 }
  51
  52 /* Testing protocol conformance */
  53
  54 - (BOOL) conformsTo: (Protocol *)aProtocolObject
  55 {
  56   size_t i;
  57   struct objc_protocol_list* proto_list;
  58
  59   if (aProtocolObject == nil)
  60     return NO;
  61
  62   if (!strcmp(aProtocolObject->protocol_name, self->protocol_name))
  63     return YES;
  64
  65   for (proto_list = protocol_list; proto_list; proto_list = proto_list->next)
  66     {
  67       for (i=0; i < proto_list->count; i++)
  68         {
  69           if ([proto_list->list[i] conformsTo: aProtocolObject])
  70             return YES;
  71         }
  72     }
  73
  74   return NO;
  75 }
  76
  77 /* Looking up information specific to a protocol */
  78
  79 - (struct objc_method_description *) descriptionForInstanceMethod:(SEL)aSel
  80 {
  81   int i;
  82   struct objc_protocol_list* proto_list;
  83   const char* name = sel_get_name (aSel);
  84   struct objc_method_description *result;
  85
  86   if (instance_methods)
  87     for (i = 0; i < instance_methods->count; i++)
  88       {
  89         if (!strcmp ((char*)instance_methods->list[i].name, name))
  90           return &(instance_methods->list[i]);
  91       }
  92
  93   for (proto_list = protocol_list; proto_list; proto_list = proto_list->next)
  94     {
  95       size_t j;
  96       for (j=0; j < proto_list->count; j++)
  97         {
  98           if ((result = [proto_list->list[j]
  99                          descriptionForInstanceMethod: aSel]))
 100             return result;
 101         }
 102     }
 103
 104   return NULL;
 105 }
 106
 107 - (struct objc_method_description *) descriptionForClassMethod:(SEL)aSel;
 108 {
 109   int i;
 110   struct objc_protocol_list* proto_list;
 111   const char* name = sel_get_name (aSel);
 112   struct objc_method_description *result;
 113
 114   if (class_methods)
 115     for (i = 0; i < class_methods->count; i++)
 116       {
 117         if (!strcmp ((char*)class_methods->list[i].name, name))
 118           return &(class_methods->list[i]);
 119       }
 120
 121   for (proto_list = protocol_list; proto_list; proto_list = proto_list->next)
 122     {
 123       size_t j;
 124       for (j=0; j < proto_list->count; j++)
 125         {
 126           if ((result = [proto_list->list[j]
 127                          descriptionForClassMethod: aSel]))
 128             return result;
 129         }
 130     }
 131
 132   return NULL;
 133 }
 134
 135 - (unsigned) hash
 136 {
 137   /* Compute a hash of the protocol_name; use the same hash algorithm
 138    * that we use for class names; protocol names and class names are
 139    * somewhat similar types of string spaces.
 140    */
 141   int hash = 0, index;
 142
 143   for (index = 0; protocol_name[index] != '\0'; index++)
 144     {
 145       hash = (hash << 4) ^ (hash >> 28) ^ protocol_name[index];
 146     }
 147
 148   hash = (hash ^ (hash >> 10) ^ (hash >> 20));
 149
 150   return hash;
 151 }
 152
 153 /*
 154  * Equality between formal protocols is only formal (nothing to do
 155  * with actually checking the list of methods they have!).  Two formal
 156  * Protocols are equal if and only if they have the same name.
 157  *
 158  * Please note (for comparisons with other implementations) that
 159  * checking the names is equivalent to checking that Protocol A
 160  * conforms to Protocol B and Protocol B conforms to Protocol A,
 161  * because this happens iff they have the same name.  If they have
 162  * different names, A conforms to B if and only if A includes B, but
 163  * the situation where A includes B and B includes A is a circular
 164  * dependency between Protocols which is forbidden by the compiler, so
 165  * A conforms to B and B conforms to A with A and B having different
 166  * names is an impossible case.
 167  */
 168 - (BOOL) isEqual: (id)obj
 169 {
 170   if (obj == self)
 171     return YES;
 172
 173   if ([obj isKindOf: [Protocol class]])
 174     {
 175       if (strcmp (protocol_name, ((Protocol *)obj)->protocol_name) == 0)
 176         return YES;
 177     }
 178
 179   return NO;
 180 }
 181 @end
 182