Improved implementation

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@19182 72102866-910b-0410-8b05-ffd578937521

Source/NSProtocolChecker.m

@@ -1,9 +1,9 @@
 /** Implementation of NSProtocolChecker for GNUStep
    Copyright (C) 1995 Free Software Foundation, Inc.
 
-   Written by:  Mike Kienenberger
+   Original by:  Mike Kienenberger
    Date: Jun 1998
-   Rewrite: Richard Frith-Macdonald
+   Written: Richard Frith-Macdonald
    Date: April 2004
 
    This file is part of the GNUstep Base Library.
@@ -36,11 +36,9 @@
 @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.
+ * Allocates and initializes an NSProtocolChecker instance by calling
+ * -initWithTarget:protocol:<br />
+ * Autoreleases and returns the new instance.
  */
 + (id) protocolCheckerWithTarget: (NSObject*)anObject
 			protocol: (Protocol*)aProtocol
@@ -55,24 +53,65 @@
   [super dealloc];
 }
 
+- (struct objc_method_description*) _methodDescription: (SEL)aSelector
+{
+  extern struct objc_method_description	*GSDescriptionForInstanceMethod();
+  extern struct objc_method_description	*GSDescriptionForClassMethod();
+
+  if (_myProtocol != nil && _myTarget != nil)
+    {
+      struct objc_method_description* mth;
+
+      /* Older gcc versions may not initialise Protocol objects properly
+       * so we have an evil hack which checks for a known bad value of
+       * the class pointer, and uses an internal function
+       * (implemented in NSObject.m) to examine the protocol contents
+       * without sending any ObjectiveC message to it.
+       */
+      if (GSObjCIsInstance(_myTarget))
+	{
+	  if ((int)GSObjCClass(_myProtocol) == 0x2)
+	    {
+	      mth = GSDescriptionForInstanceMethod(_myProtocol, aSelector);
+	    }
+	  else
+	    {
+	      mth = [_myProtocol descriptionForInstanceMethod: aSelector];
+	    }
+	}
+      else
+	{
+	  if ((int)GSObjCClass(_myProtocol) == 0x2)
+	    {
+	      mth = GSDescriptionForClassMethod(_myProtocol, aSelector);
+	    }
+	  else
+	    {
+	      mth = [_myProtocol descriptionForClassMethod: aSelector];
+	    }
+	}
+      return mth;
+    }
+  return 0;
+}
+
 /*
  * Forwards any message to the delegate if the method is declared in
  * the checker's protocol; otherwise raises an NSInvalidArgumentException.
  */
 - (void) forwardInvocation: (NSInvocation*)anInvocation
 {
-  if (GSObjCIsInstance(_myTarget))
+  const char	*type;
+
+  if ([self _methodDescription: [anInvocation selector]] == 0)
     {
-      if (![_myProtocol descriptionForInstanceMethod: [anInvocation selector]])
+      if (GSObjCIsInstance(_myTarget))
 	{
 	  [NSException raise: NSInvalidArgumentException
 		      format: @"<%s -%@> not declared",
 	    [_myProtocol name], NSStringFromSelector([anInvocation selector])];
 	}
-    }
-  else
-    {
-      if (![_myProtocol descriptionForClassMethod: [anInvocation selector]])
+      else
 	{
 	  [NSException raise: NSInvalidArgumentException
 		      format: @"<%s +%@> not declared",
@@ -80,6 +119,23 @@
 	}
     }
   [anInvocation invokeWithTarget: _myTarget];
+
+  /*
+   * If the method returns 'self' (ie the target object) replace the
+   * returned value with the protocol checker.
+   */
+  type = [[anInvocation methodSignature] methodReturnType];
+  if (strcmp(type, @encode(id)) == 0)
+    {
+      id	buf;
+
+      [anInvocation getReturnValue: &buf];
+      if (buf == _myTarget)
+	{
+	  buf = self;
+	  [anInvocation setReturnValue: &buf];
+	}
+    }
 }
 
 - (id) init
@@ -92,9 +148,10 @@
  * 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.
+ * restrict the messages that can be sent to anObject. If any method
+ * in the protocol returns anObject, the checker will replace the returned
+ * value with itsself rather than the target object.<br />
+ * Returns the new instance.
  */
 - (id) initWithTarget: (NSObject*)anObject protocol: (Protocol*)aProtocol
 {
@@ -110,11 +167,105 @@
 
 - (NSMethodSignature*) methodSignatureForSelector: (SEL)aSelector
 {
-  if (aSelector == _cmd || [self respondsToSelector: aSelector] == YES)
+  const char		*types;
+  struct objc_method	*mth;
+  Class			c;
+
+  if (aSelector == 0)
+    [NSException raise: NSInvalidArgumentException
+		format: @"%@ null selector given", NSStringFromSelector(_cmd)];
+
+  /*
+   * Evil hack to prevent recursion - if we are asking a remote
+   * object for a method signature, we can't ask it for the
+   * signature of methodSignatureForSelector:, so we hack in
+   * the signature required manually :-(
+   */
+  if (sel_eq(aSelector, _cmd))
     {
-      return [_myTarget methodSignatureForSelector: aSelector];
+      static	NSMethodSignature	*sig = nil;
+
+      if (sig == nil)
+	{
+	  sig = [NSMethodSignature signatureWithObjCTypes: "@@::"];
+	  RETAIN(sig);
+	}
+      return sig;
     }
-  return nil;
+
+  if (_myProtocol != nil)
+    {
+      const char			*types = 0;
+      struct objc_method_description	*desc;
+
+      desc = [self _methodDescription: aSelector];
+      if (desc != 0)
+	{
+	  types = desc->types;
+	}
+      if (types == 0)
+	{
+	  return nil;
+	}
+      return [NSMethodSignature signatureWithObjCTypes: types];
+    }
+
+  c = GSObjCClass(self);
+  mth = GSGetInstanceMethod(c, aSelector);
+  if (mth == 0)
+    {
+      return nil; // Method not implemented
+    }
+  types = mth->method_types;
+
+  /*
+   * If there are protocols that this class conforms to,
+   * the method may be listed in a protocol with more
+   * detailed type information than in the class itsself
+   * and we must therefore use the information from the
+   * protocol.
+   * This is because protocols also carry information
+   * used by the Distributed Objects system, which the
+   * runtime does not maintain in classes.
+   */
+  if (c->protocols != 0)
+    {
+      struct objc_protocol_list	*protocols = c->protocols;
+      BOOL			found = NO;
+
+      while (found == NO && protocols != 0)
+	{
+	  unsigned	i = 0;
+
+	  while (found == NO && i < protocols->count)
+	    {
+	      Protocol				*p;
+	      struct objc_method_description	*pmth;
+
+	      p = protocols->list[i++];
+	      if (c == (Class)self)
+		{
+		  pmth = [p descriptionForClassMethod: aSelector];
+		}
+	      else
+		{
+		  pmth = [p descriptionForInstanceMethod: aSelector];
+		}
+	      if (pmth != 0)
+		{
+		  types = pmth->types;
+		  found = YES;
+		}
+	    }
+	  protocols = protocols->next;
+	}
+    }
+
+  if (types == 0)
+    {
+      return nil;
+    }
+  return [NSMethodSignature signatureWithObjCTypes: types];
 }
 
 /**
@@ -126,25 +277,6 @@
   return _myProtocol;
 }
 
-- (BOOL) respondsToSelector: (SEL)aSelector
-{
-  if (GSObjCIsInstance(_myTarget))
-    {
-      if ([_myProtocol descriptionForInstanceMethod: aSelector])
-	{
-	  return YES;
-	}
-    }
-  else
-    {
-      if ([_myProtocol descriptionForClassMethod: aSelector])
-	{
-	  return YES;
-	}
-    }
-  return NO;
-}
-
 /**
  * Returns the target of the NSProtocolChecker.
  */