Implement fast enumeration for GSMutableOrderedSet.

Implement fast version of getObjects:range: in GSOrderedSet. This
gets used for fast enumeration.
Base the array method on fast enumeration.

Source/GSOrderedSet.m

@@ -227,6 +227,21 @@ static Class	mutableSetClass;
   return item.obj;
 }
 
+- (void) getObjects: (__unsafe_unretained id[])aBuffer range: (NSRange)aRange
+{
+  NSUInteger i, j = 0;
+  NSUInteger c = GSIArrayCount(&array);
+  NSUInteger e = NSMaxRange(aRange);
+
+  GS_RANGE_CHECK(aRange, c);
+
+  for (i = aRange.location; i < e; i++)
+    {
+      GSIArrayItem item = GSIArrayItemAtIndex(&array, i);
+      aBuffer[j++] = item.obj;
+    }
+}
+
 /* Designated initialiser */
 - (id) initWithObjects: (const id*)objs count: (NSUInteger)c
 {
@@ -345,4 +360,33 @@ static Class	mutableSetClass;
   return self;
 }
 
+- (NSUInteger) countByEnumeratingWithState: (NSFastEnumerationState *)state
+				   objects: (__unsafe_unretained id[])stackbuf
+				     count: (NSUInteger)len
+{
+  NSInteger count;
+
+  /* This is cached in the caller at the start and compared at each
+   * iteration.   If it changes during the iteration then
+   * objc_enumerationMutation() will be called, throwing an exception.
+   */
+  state->mutationsPtr = &_version;
+  count = MIN(len, [self count] - state->state);
+  /* If a mutation has occurred then it's possible that we are being asked to
+   * get objects from after the end of the array.  Don't pass negative values
+   * to memcpy.
+   */
+  if (count > 0)
+    {
+      [self getObjects: stackbuf range: NSMakeRange(state->state, count)];
+      state->state += count;
+    }
+  else
+    {
+      count = 0;
+    }
+  state->itemsPtr = stackbuf;
+  return count;
+}
+
 @end

Source/NSOrderedSet.m

@@ -1263,14 +1263,12 @@ static SEL	remSel;
 
 - (NSArray *) array
 {
-  NSEnumerator *en = [self objectEnumerator];
   NSMutableArray *result = [NSMutableArray arrayWithCapacity: [self count]];
-  id o = nil;
+  id<NSFastEnumeration> enumerator = self;
 
-  while((o = [en nextObject]) != nil)
-    {
+  FOR_IN(id, o, enumerator)
       [result addObject: o];
-    }
+  END_FOR_IN(enumerator)
 
   return GS_IMMUTABLE(result);
 }