diff --git a/common/list.c b/common/list.c
index 66d52f700..bd9abcd82 100644
--- a/common/list.c
+++ b/common/list.c
@@ -147,3 +147,61 @@ void list_stable_sort(list_t *list, int compare(const void *a, const void *b)) {
 		list_inplace_sort(list, 0, list->length - 1, compare);
 	}
 }
+
+void list_sortedset_insert(list_t *list, void *item,
+		int compare(const void *item_left, const void *item_right),
+		void *replace(void *old_item, void* new_item)) {
+	if (list->length <= 0) {
+		list_add(list, item);
+		return;
+	}
+
+	size_t lower = 0;
+	size_t upper = (size_t)list->length - 1;
+	while (lower <= upper && upper != (size_t)-1) {
+		size_t div = (lower + upper) / 2;
+		int cv = compare(list->items[div], item);
+		if (cv < 0) {
+			lower = div + 1;
+		} else if (cv > 0) {
+			upper = div - 1;
+		} else {
+			list->items[div] = replace(list->items[div], item);
+			return;
+		}
+	}
+	list_insert(list, lower, item);
+}
+
+int list_sortedset_find(list_t *list,
+		int compare(const void *item, const void *cmp_to),
+		const void *cmp_to) {
+	if (list->length <= 0) {
+		return -1;
+	}
+
+	size_t lower = 0;
+	size_t upper = (size_t)list->length - 1;
+	while (lower <= upper && upper != (size_t)-1) {
+		size_t div = (lower + upper) / 2;
+		int cv = compare(list->items[div], cmp_to);
+		if (cv < 0) {
+			lower = div + 1;
+		} else if (cv > 0) {
+			upper = div - 1;
+		} else {
+			return div;
+		}
+	}
+	return -1;
+}
+
+int list_is_sortedset(list_t *list,
+		int compare(const void *left, const void *right)) {
+	for (size_t i = 1; i < (size_t)list->length; i++) {
+		if (compare(list->items[i - 1], list->items[i]) >= 0) {
+			return 0;
+		}
+	}
+	return 1;
+}
diff --git a/include/list.h b/include/list.h
index 5a0d7d809..e610bb7e9 100644
--- a/include/list.h
+++ b/include/list.h
@@ -12,6 +12,12 @@ void list_free(list_t *list);
 void list_foreach(list_t *list, void (*callback)(void* item));
 void list_add(list_t *list, void *item);
 void list_insert(list_t *list, int index, void *item);
+// Insert an item into the list which is already sorted strictly ascending
+// according to 'compare'. 'replace' is called when displacing an old item
+// and returns the item which will take its place.
+void list_sortedset_insert(list_t *list, void* item,
+		int compare(const void *item_left, const void *item_right),
+		void *replace(void *old_item, void* new_item));
 void list_del(list_t *list, int index);
 void list_cat(list_t *list, list_t *source);
 // See qsort. Remember to use *_qsort functions as compare functions,
@@ -20,6 +26,11 @@ void list_qsort(list_t *list, int compare(const void *left, const void *right));
 // Return index for first item in list that returns 0 for given compare
 // function or -1 if none matches.
 int list_seq_find(list_t *list, int compare(const void *item, const void *cmp_to), const void *cmp_to);
+// Requires a list sorted strictly ascending according to 'compare';
+// returns the index of the matching item, or -1 is no such item exists
+int list_sortedset_find(list_t *list, int compare(const void *item, const void *cmp_to), const void *cmp_to);
+// Check if a list is sorted strictly ascending according to compare
+int list_is_sortedset(list_t *list, int compare(const void *left, const void *right));
 // stable sort since qsort is not guaranteed to be stable
 void list_stable_sort(list_t *list, int compare(const void *a, const void *b));
 // swap two elements in a list