vm: rework object iteration

Ensure that deleting object keys during iteration is safe by keeping a
global chain of per-object iterators which are advanced to the next key
when the entry that is about to be iterated is deleted.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 36 insertions, 0 deletions

diff --git a/include/ucode/types.h b/include/ucode/types.h
index 7fcc7f1..c0ccd38 100644
--- a/include/ucode/types.h
+++ b/include/ucode/types.h
@@ -207,6 +207,16 @@ typedef struct {
 uc_declare_vector(uc_resource_types_t, uc_resource_type_t *);
 
 
+/* Object iteration */
+
+extern uc_list_t uc_object_iterators;
+
+typedef struct {
+	uc_list_t list;
+	struct lh_entry *pos;
+} uc_object_iterator_t;
+
+
 /* Program structure definitions */
 
 uc_declare_vector(uc_sources_t, uc_source_t *);
diff --git a/include/ucode/util.h b/include/ucode/util.h
index 52303cc..a3692d5 100644
--- a/include/ucode/util.h
+++ b/include/ucode/util.h
@@ -79,6 +79,32 @@
 } while(0)
 
 
+/* linked lists */
+
+typedef struct uc_list {
+	struct uc_list *prev;
+	struct uc_list *next;
+} uc_list_t;
+
+static inline void uc_list_insert(uc_list_t *list, uc_list_t *item)
+{
+	list->next->prev = item;
+	item->next = list->next;
+	item->prev = list;
+	list->next = item;
+}
+
+static inline void uc_list_remove(uc_list_t *item)
+{
+	item->next->prev = item->prev;
+	item->prev->next = item->next;
+	item->prev = item->next = item;
+}
+
+#define uc_list_foreach(item, list) \
+	for (uc_list_t *item = (list)->next; item != (list); item = item->next)
+
+
 /* "failsafe" utility functions */
 
 static inline void *xcalloc(size_t size, size_t nmemb) {