map: add map_leaf utility function

Tests whether the given prefix can be extended to exactly one map element
i.e. true iff the prefix map contains exactly one element.

1 files changed, 13 insertions, 0 deletions

diff --git a/map.c b/map.c
index 7994f34..94e941c 100644
--- a/map.c
+++ b/map.c
@@ -78,6 +78,19 @@ bool map_contains(const Map *map, const char *prefix)
 	return !map_empty(map_prefix(map, prefix));
 }
 
+static bool leaf(const char *key, void *value, void *data)
+{
+	int *nodes = data;
+	return (*nodes)++ < 1;
+}
+
+bool map_leaf(const Map *map, const char *prefix)
+{
+	int nodes = 0;
+	map_iterate(map_prefix(map, prefix), leaf, &nodes);
+	return nodes == 1;
+}
+
 bool map_put(Map *map, const char *k, const void *value)
 {
 	size_t len = strlen(k);