libs-base/Source/NSProtocolChecker.m

/** Implementation of NSProtocolChecker for GNUStep
   Copyright (C) 1995 Free Software Foundation, Inc.

   Written by:  Mike Kienenberger
   Date: Jun 1998
   
   This file is part of the GNUstep Base 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., 59 Temple Place, Suite 330, Boston, MA 02111 USA.

   <title>NSProtocolChecker class reference</title>
   $Date$ $Revision$
   */ 

#include "config.h"
#include <base/preface.h>
#include <Foundation/NSProtocolChecker.h>
#include <Foundation/NSException.h>
#include <Foundation/NSInvocation.h>
#include <Foundation/NSMethodSignature.h>

@implementation NSProtocolChecker

/*
 * Allocates and initializes an NSProtocolChecker instance that will
 * forward any messages in the aProtocol protocol to anObject, its
 * target. Thus, the checker can be vended in lieu of anObject to
 * restrict the messages that can be sent to anObject. Returns the
 * new instance.
 */

+ (id) protocolCheckerWithTarget: (NSObject*)anObject
			protocol: (Protocol*)aProtocol
{
  return AUTORELEASE([[NSProtocolChecker alloc] initWithTarget: anObject
						      protocol: aProtocol]);
}

/*
 * Forwards any message to the delegate if the method is declared in
 * the checker's protocol; otherwise raises an NSInvalidArgumentException.
 */
- (void) forwardInvocation: (NSInvocation*)anInvocation
{
  unsigned int	length;
  void		*buffer;
  
  if ((struct objc_method_description *)NULL
    != [self methodDescriptionForSelector: [anInvocation selector]])
    [[NSException exceptionWithName: NSInvalidArgumentException
		  reason: @"Method not declared in current protocol"
		  userInfo: nil] raise];
      
  [anInvocation invokeWithTarget: _myTarget];
  
  length = [[anInvocation methodSignature] methodReturnLength];
  buffer = (void *)malloc(length);
  [anInvocation getReturnValue: buffer];
  
  if (0 == strcmp([[anInvocation methodSignature] methodReturnType],
		  [[anInvocation methodSignatureForSelector: 
				  @selector(init: )] methodReturnType]) )
    {
      if (((id)buffer) == _myTarget)
   	{
	  ((id)buffer) = self;
	  [anInvocation setReturnValue: buffer];
   	}
    }
  
  return;
}


- (id) init
{
  _myProtocol = nil;
  _myTarget = nil;
  
  return self;
}

/*
 * Initializes a newly allocated NSProtocolChecker instance that will
 * forward any messages in the aProtocol protocol to anObject, its
 * delegate. Thus, the checker can be vended in lieu of anObject to
 * restrict the messages that can be sent to anObject. If anObject is
 * allowed to be freed or dereferenced by clients, the free method
 * should be included in aProtocol. Returns the new instance.
 */
- (id) initWithTarget: (NSObject*)anObject protocol: (Protocol*)aProtocol
{
  [super init];
  
  _myProtocol = aProtocol;
  
  ASSIGN(_myTarget, anObject);
  
  return self;
}

/*
 * Returns an Objective C description for a method in the checker's
 * protocol, or NULL if aSelector isn't declared as an instance method
 * in the protocol.
 */
- (struct objc_method_description*) methodDescriptionForSelector: (SEL)aSelector
{
  return [_myProtocol descriptionForInstanceMethod: aSelector];
}

/*
 * Returns the protocol object the checker uses to verify whether a
 * given message should be forwarded to its delegate, or the protocol
 * checker should raise an NSInvalidArgumentException.
 */
- (Protocol*) protocol
{
  if (nil == _myProtocol)
    [[NSException exceptionWithName: NSInvalidArgumentException
		  reason: @"No protocol specified"
		  userInfo: nil] raise];
  
  return _myProtocol;
}

/*
 * Returns the target of the NSProtocolChecker.
 */
- (NSObject*) target
{
  return _myTarget;
}

@end