From ff6cf34ee7a8db747d8284b5c5532f8d13b7cea5 Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Thu, 5 Mar 2015 08:13:42 +0100
Subject: [PATCH] avltree: Add sdb_avltree_iter_peek_next().

The function returns the next element without advancing the iterator.
---
 src/include/utils/avltree.h | 12 ++++++++++++
 src/utils/avltree.c         |  8 ++++++++
 t/unit/utils/avltree_test.c | 13 +++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/src/include/utils/avltree.h b/src/include/utils/avltree.h
index de51c7e..ba495c6 100644
--- a/src/include/utils/avltree.h
+++ b/src/include/utils/avltree.h
@@ -113,6 +113,18 @@ sdb_avltree_iter_has_next(sdb_avltree_iter_t *iter);
 sdb_object_t *
 sdb_avltree_iter_get_next(sdb_avltree_iter_t *iter);
 
+/*
+ * sdb_avltree_iter_peek_next:
+ * Peek at the next node, if there is one. This is similar to has_next() but
+ * it returns the actual next element without advancing the iterator.
+ *
+ * Returns:
+ *  - the next node, if there is one
+ *  - NULL else
+ */
+sdb_object_t *
+sdb_avltree_iter_peek_next(sdb_avltree_iter_t *iter);
+
 /*
  * sdb_avltree_size:
  * Returns the number of nodes in the tree.
diff --git a/src/utils/avltree.c b/src/utils/avltree.c
index 54c1895..87db2f7 100644
--- a/src/utils/avltree.c
+++ b/src/utils/avltree.c
@@ -457,6 +457,14 @@ sdb_avltree_iter_get_next(sdb_avltree_iter_t *iter)
 	return n ? n->obj : NULL;
 } /* sdb_avltree_iter_get_next */
 
+sdb_object_t *
+sdb_avltree_iter_peek_next(sdb_avltree_iter_t *iter)
+{
+	if ((! iter) || (! iter->node))
+		return NULL;
+	return iter->node->obj;
+} /* sdb_avltree_iter_peek_next */
+
 size_t
 sdb_avltree_size(sdb_avltree_t *tree)
 {
diff --git a/t/unit/utils/avltree_test.c b/t/unit/utils/avltree_test.c
index 9be5e09..433f67d 100644
--- a/t/unit/utils/avltree_test.c
+++ b/t/unit/utils/avltree_test.c
@@ -209,11 +209,17 @@ START_TEST(test_iter)
 
 	for (i = 0; i < SDB_STATIC_ARRAY_LEN(test_data); ++i) {
 		char expected_name[] = { (char)('a' + (int)i), '\0' };
+		sdb_object_t *expected_obj;
 
 		_Bool c = sdb_avltree_iter_has_next(iter);
 		fail_unless(c, "sdb_avltree_iter_has_next(<iter[%zu]>) = false; "
 				"expected: true", i);
 
+		expected_obj = sdb_avltree_iter_peek_next(iter);
+		fail_unless(expected_obj != NULL,
+				"sdb_avltree_iter_peek_next(<iter[%zu]>) = NULL; "
+				"expected: <obj>", i);
+
 		obj = sdb_avltree_iter_get_next(iter);
 		fail_unless(obj != NULL,
 				"sdb_avltree_iter_get_next(<iter[%zu]>) = NULL; "
@@ -221,11 +227,18 @@ START_TEST(test_iter)
 		fail_unless(!strcmp(obj->name, expected_name),
 				"sdb_avltree_iter[%zu] = %s; expected: %s",
 				i, obj->name, expected_name);
+
+		fail_unless(obj == expected_obj,
+				"sdb_avltree_iter_get_next(<iter[%zu]>) = %p; "
+				"expected: %p (from peek())", i, obj, expected_obj);
 	}
 
 	check = sdb_avltree_iter_has_next(iter) != 0;
 	fail_unless(check == 0, "sdb_avltree_iter_has_next(<iter>) = true; "
 			"expected: false");
+	obj = sdb_avltree_iter_peek_next(iter);
+	fail_unless(obj == NULL,
+			"sdb_avltree_iter_peek_next(<iter>) = <obj>; expected: NULL");
 	obj = sdb_avltree_iter_get_next(iter);
 	fail_unless(obj == NULL,
 			"sdb_avltree_iter_get_next(<iter>) = <obj>; expected: NULL");
-- 
2.30.2