add methods to keep the entire tree from getting deallocated while there are any external references to any object in the tree

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/branches/nsxml_using_libxml2@34579 72102866-910b-0410-8b05-ffd578937521

Source/NSXMLElement.m

@@ -335,6 +335,10 @@ extern void clearPrivatePointers(xmlNodePtr aNode);
     {
       nextNode->prev = newNode;
     }
+  if(prevNode != NULL)
+    {
+      prevNode->next = newNode;
+    }
 
   if(MY_NODE->children == NULL)
     {
@@ -342,7 +346,8 @@ extern void clearPrivatePointers(xmlNodePtr aNode);
     }
 
   ((xmlNodePtr)[child _node])->parent = [self _node];
-  GSIVar(child, parent) = self;
+  //GSIVar(child, parent) = self;
+  [self _addSubNode:child];
 }
 
 - (void) insertChildren: (NSArray*)children atIndex: (NSUInteger)index

Source/NSXMLNode.m

@@ -540,6 +540,50 @@ NSArray *execute_xpath(NSXMLNode *node,
   return c;
 }
 
+- (void) recordExternalRetain
+{
+  id parent = [self parent];
+  if (parent)
+    [parent recordExternalRetain];
+  else
+    {
+      if (internal->externalRetains == 0)
+         [super retain]; // the top of the tree retains itself whenever there are external retains anywhere
+      internal->externalRetains++;
+    }
+}
+
+- (void) releaseExternalRetain
+{
+  id parent = [self parent];
+  if (parent)
+    [parent releaseExternalRetain];
+  else
+    {
+      internal->externalRetains--;
+      if (internal->externalRetains == 0)
+         [super release]; // the top of the tree retains itself whenever there are external retains anywhere
+    }
+}
+
+- (id) retain
+{
+  if ([self retainCount] == 1)
+    {
+      [self recordExternalRetain];
+    }
+  return [super retain];
+}
+
+- (void) release
+{
+  if ([self retainCount] == 2)
+    {
+      [self releaseExternalRetain];
+    }
+  [super release];
+}
+
 - (void) dealloc
 {
   if (GS_EXISTS_INTERNAL)
@@ -548,8 +592,10 @@ NSArray *execute_xpath(NSXMLNode *node,
       [internal->URI release];
       [internal->objectValue release];
       [internal->subNodes release];
-      [self detach];
-      xmlFree(node);
+      if (node->parent == NULL)
+	{
+	  xmlFree(node);  // the top level node frees the entire tree
+	}
       GS_DESTROY_INTERNAL(NSXMLNode);
     }
   [super dealloc];

Source/NSXMLPrivate.h

@@ -113,6 +113,8 @@ StringFromXMLString(const unsigned char *bytes, unsigned length)
   void           *node;  \
   NSMutableArray *subNodes; \
   NSString       *xpath; \
+  int		externalRetains; \
+
 
 /* When using the non-fragile ABI, the instance variables are exposed to the
  * compiler within the class declaration, so we don't need to incorporate