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/** Behaviors for Objective-C, "for Protocols with implementations".
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Copyright (C) 1995, 1996 Free Software Foundation, Inc.
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Written by: Andrew Kachites McCallum <mccallum@gnu.ai.mit.edu>
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This file is part of the GNUstep Base Library.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free
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Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111 USA.
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/* A Behavior can be seen as a "Protocol with an implementation" or a
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"Class without any instance variables". A key feature of behaviors
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is that they give a degree of multiple inheritance.
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Behavior methods, when added to a class, override the class's
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superclass methods, but not the class's methods.
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xxx not necessarily on the "no instance vars". The behavior just has
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to have the same layout as the class.
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The following function is a sneaky hack way that provides Behaviors
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without adding any new syntax to the Objective C language. Simply
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define a class with the methods you want in the behavior, then call
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this function with that class as the BEHAVIOR argument.
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This function should be called in CLASS's +initialize method.
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If you add several behaviors to a class, be aware that the order of
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the additions is significant.
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McCallum talking to himself:
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"Yipes. Be careful with [super ...] calls.
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BEHAVIOR methods running in CLASS will now have a different super class.
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No; wrong. See objc-api.h; typedef struct objc_super."
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#include "GNUstepBase/preface.h"
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#include "GNUstepBase/behavior.h"
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#ifndef NeXT_Foundation_LIBRARY
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#include <Foundation/NSException.h>
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#include <Foundation/NSString.h>
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#include <Foundation/Foundation.h>
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static BOOL class_is_kind_of(Class self, Class class);
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static int behavior_debug = 0;
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behavior_set_debug(int i)
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behavior_class_add_class (Class class, Class behavior)
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Class behavior_super_class = class_get_super_class(behavior);
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NSCAssert(CLS_ISCLASS(class), NSInvalidArgumentException);
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NSCAssert(CLS_ISCLASS(behavior), NSInvalidArgumentException);
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NSCAssert2(class->instance_size >= behavior->instance_size,
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@"Trying to add behavior (%s) with instance size larger than class (%s)",
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class_get_class_name(behavior), class_get_class_name(class));
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/* If necessary, increase instance_size of CLASS. */
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if (class->instance_size < behavior->instance_size)
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NSCAssert(!class->subclass_list,
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@"The behavior-addition code wants to increase the\n"
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@"instance size of a class, but it cannot because you\n"
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@"have subclassed the class. There are two solutions:\n"
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@"(1) Don't subclass it; (2) Add placeholder instance\n"
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@"variables to the class, so the behavior-addition code\n"
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@"will not have to increase the instance size\n");
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class->instance_size = behavior->instance_size;
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fprintf(stderr, "Adding behavior to class %s\n",
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/* Add instance methods */
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fprintf(stderr, "Adding instance methods from %s\n",
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struct objc_method_list *method_list;
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while ((method_list = class_nextMethodList(behavior, &iterator)))
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behavior_class_add_methods (class, method_list);
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behavior_class_add_methods (class, behavior->methods);
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/* Add class methods */
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fprintf(stderr, "Adding class methods from %s\n",
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behavior->class_pointer->name);
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struct objc_method_list *method_list;
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while ((method_list =
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class_nextMethodList(behavior->class_pointer, &iterator)))
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behavior_class_add_methods (class->class_pointer, method_list);
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behavior_class_add_methods (class->class_pointer,
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behavior->class_pointer->methods);
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/* Add behavior's superclass, if not already there. */
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if (!class_is_kind_of(class, behavior_super_class))
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behavior_class_add_class (class, behavior_super_class);
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behavior_class_add_category (Class class, struct objc_category *category)
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behavior_class_add_methods (class,
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category->instance_methods);
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behavior_class_add_methods (class->class_pointer,
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category->class_methods);
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/* xxx Add the protocols (category->protocols) too. */
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static struct objc_method *search_for_method_in_list (Class class, SEL op);
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behavior_class_add_methods (Class class, struct objc_method_list *methods)
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static SEL initialize_sel = 0;
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struct objc_method_list *mlist;
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initialize_sel = sel_register_name ("initialize");
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/* Add methods to class->dtable and class->methods */
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struct objc_method_list *new_list;
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counter = mlist->method_count ? mlist->method_count - 1 : 1;
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/* This is a little wasteful of memory, since not necessarily
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all methods will go in here. */
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new_list = (struct objc_method_list *)
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objc_malloc (sizeof(struct objc_method_list) +
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sizeof(struct objc_method[counter+1]));
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new_list->method_count = 0;
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struct objc_method *method = &(mlist->method_list[counter]);
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fprintf(stderr, " processing method [%s] ... ",
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sel_get_name(method->method_name));
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if (!search_for_method_in_list(class,method->method_name)
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&& !sel_eq(method->method_name, initialize_sel))
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/* As long as the method isn't defined in the CLASS,
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put the BEHAVIOR method in there. Thus, behavior
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methods override the superclasses' methods. */
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new_list->method_list[new_list->method_count] = *method;
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(new_list->method_count)++;
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fprintf(stderr, "added.\n");
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else if (behavior_debug)
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fprintf(stderr, "ignored.\n");
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if (new_list->method_count)
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class_add_method_list(class, new_list);
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/* Search for the named method's method structure. Return a pointer
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to the method's method structure if found. NULL otherwise. */
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static struct objc_method *
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search_for_method_in_list (Class class, SEL op)
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struct objc_method_list *method_list;
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if (! sel_is_mapped (op))
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/* If not found then we'll search the list. */
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while ((method_list = class_nextMethodList(class, &iterator)))
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/* Search the method list. */
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for (i = 0; i < method_list->method_count; ++i)
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struct objc_method *method = &method_list->method_list[i];
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if (method->method_name)
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if (sel_eq(method->method_name, op))
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* The following two functions are implemented in the GNU objc runtime
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extern Method_t search_for_method_in_list(MethodList_t list, SEL op);
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extern void class_add_method_list(Class, MethodList_t);
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behavior_class_add_methods (Class class,
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struct objc_method_list *methods)
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static SEL initialize_sel = 0;
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struct objc_method_list *mlist;
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initialize_sel = sel_register_name ("initialize");
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/* Add methods to class->dtable and class->methods */
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for (mlist = methods; mlist; mlist = mlist->method_next)
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struct objc_method_list *new_list;
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counter = mlist->method_count ? mlist->method_count - 1 : 1;
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/* This is a little wasteful of memory, since not necessarily
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all methods will go in here. */
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new_list = (struct objc_method_list *)
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objc_malloc (sizeof(struct objc_method_list) +
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sizeof(struct objc_method[counter+1]));
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new_list->method_count = 0;
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new_list->method_next = NULL;
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struct objc_method *method = &(mlist->method_list[counter]);
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const char *name = sel_get_name(method->method_name);
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fprintf(stderr, " processing method [%s] ... ", name);
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if (!search_for_method_in_list(class->methods, method->method_name)
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&& !sel_eq(method->method_name, initialize_sel))
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/* As long as the method isn't defined in the CLASS,
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put the BEHAVIOR method in there. Thus, behavior
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methods override the superclasses' methods. */
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new_list->method_list[new_list->method_count] = *method;
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* HACK ... the GNU runtime implementation of
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* class_add_method_list() expects the method names to be
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* C-strings rather than selectors ... so we must allow
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new_list->method_list[new_list->method_count].method_name
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(new_list->method_count)++;
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fprintf(stderr, "added.\n");
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else if (behavior_debug)
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fprintf(stderr, "ignored.\n");
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if (new_list->method_count)
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class_add_method_list(class, new_list);
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#endif /* NeXT runtime */
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static BOOL class_is_kind_of(Class self, Class aClassObject)
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for (class = self; class!=Nil; class = class_get_super_class(class))
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if (class==aClassObject)
added
removed
Source/Additions/behavior.m
