implemented more flexible iterator hook API

kernel interface handles interface changes and updates address list

src/libstrongswan/utils/iterator.h

@@ -26,15 +26,46 @@
 
 #include <library.h>
 
+typedef enum hook_result_t hook_result_t;
+
+/**
+ * @brief Return value of an iterator hook.
+ *
+ * Returning HOOK_AGAIN is useful to "inject" additional elements in an
+ * iteration, HOOK_NEXT is the normal iterator behavior, and HOOK_SKIP may
+ * be used to filter elements out.
+ *
+ * @ingroup utils
+ */
+enum hook_result_t {
+
+	/**
+	 * A value was placed in out, hook is called again with the same "in"
+	 */
+	HOOK_AGAIN,
+	
+	/**
+	 * A value was placed in out, hook is called again with next "in" (if any)
+	 */
+	HOOK_NEXT,
+	
+	/**
+	 * No value in out, call again with next "in" (if any)
+	 */
+	HOOK_SKIP,
+};
+
 /**
  * @brief Iterator hook function prototype.
  *
  * @param param		user supplied parameter
  * @param in		the value the hook receives from the iterator
  * @param out		the value supplied as a result to the iterator
- * @return			TRUE to return "out", FALSE to skip this value
+ * @return			a hook_result_t
+ *
+ * @ingroup utils
  */
-typedef bool (iterator_hook_t)(void *param, void *in, void **out);
+typedef hook_result_t (iterator_hook_t)(void *param, void *in, void **out);
 
 
 typedef struct iterator_t iterator_t;
@@ -45,8 +76,6 @@ typedef struct iterator_t iterator_t;
  * iterator_t defines an interface for iterating over collections.
  * It allows searching, deleting, updating and inserting.
  *
- * Thanks to JMP for iterator lessons :-)
- *
  * @b Constructors:
  * - via linked_list_t.create_iterator, or
  * - any other class which supports the iterator_t interface
@@ -84,8 +113,11 @@ struct iterator_t {
 	 * Sometimes it is useful to hook in an iterator. The hook function is
 	 * called before any successful return of iterate(). It takes the
 	 * iterator value, may manipulate it (or the references object), and returns
-	 * the value that the iterate() function returns.
+	 * the value that the iterate() function returns. Depending on the hook
+	 * return value, the hook is called again, called with next, or skipped.
 	 * A value of NULL deactivates the iterator hook.
+	 * If an iterator is hooked, only the iterate() method is valid,
+	 * all other methods behave undefined.
 	 * 
 	 * @param this 			calling object
 	 * @param hook			iterator hook which manipulates the iterated value

src/libstrongswan/utils/linked_list.c

@@ -151,10 +151,10 @@ static int get_list_count(private_iterator_t *this)
 /**
  * default iterator hook which does nothing
  */
-static bool iterator_hook(void *param, void *in, void **out)
+static hook_result_t iterator_hook(void *param, void *in, void **out)
 {
 	*out = in;
-	return TRUE;
+	return HOOK_NEXT;
 }
 
 /**
@@ -180,40 +180,43 @@ static void set_iterator_hook(private_iterator_t *this, iterator_hook_t *hook,
  */
 static bool iterate(private_iterator_t *this, void** value)
 {
-	if (this->list->count == 0)
+	while (TRUE)
 	{
-		return FALSE;
-	}
-	if (this->current == NULL)
-	{
-		this->current = (this->forward) ? this->list->first : this->list->last;
-		if (!this->hook(this->hook_param, this->current->value, value))
+		if (this->forward)
 		{
-			return iterate(this, value);
+			this->current = this->current ? this->current->next : this->list->first;
 		}
-		return TRUE;
-	}
-	if (this->forward)
-	{
-		if (this->current->next == NULL)
+		else
+		{
+			this->current = this->current ? this->current->previous : this->list->last;
+		}
+
+		if (this->current == NULL)
 		{
 			return FALSE;
 		}
-		this->current = this->current->next;
-		if (!this->hook(this->hook_param, this->current->value, value))
+	
+		switch (this->hook(this->hook_param, this->current->value, value))
 		{
-			return iterate(this, value);
+			case HOOK_AGAIN:
+				/* rewind */
+				if (this->forward)
+				{
+					this->current = this->current->previous;
+				}
+				else
+				{
+					this->current = this->current->next;
+				}
+				break;
+			case HOOK_NEXT:
+				/* normal iteration */
+				break;
+			case HOOK_SKIP:
+				/* advance */
+				continue;
 		}
-		return TRUE;
-	}
-	if (this->current->previous == NULL)
-	{
-		return FALSE;
-	}
-	this->current = this->current->previous;
-	if (!this->hook(this->hook_param, this->current->value, value))
-	{
-		return iterate(this, value);
+		break;
 	}
 	return TRUE;
 }