Add 'undo_ptr_list_last()' helper function

It's like 'delete_ptr_list_last()', except it doesn't de-allocate the
ptrlist block that it removes the last entry from.  Useful when you know
you're going to add things back (ie basic block tail rewriting), and
when you can't afford to de-allocate the ptrlist because you're in a
loop.

1 files changed, 21 insertions, 0 deletions

diff --git a/ptrlist.c b/ptrlist.c
index 065891c..14d8416 100644
--- a/ptrlist.c
+++ b/ptrlist.c
@@ -177,6 +177,27 @@ out:
 	return count;
 }
 
+/* This removes the last entry, but doesn't pack the ptr list */
+void * undo_ptr_list_last(struct ptr_list **head)
+{
+	struct ptr_list *last, *first = *head;
+
+	if (!first)
+		return NULL;
+	last = first;
+	do {
+		last = last->prev;
+		if (last->nr) {
+			void *ptr;
+			int nr = --last->nr;
+			ptr = last->list[nr];
+			last->list[nr] = (void *)0xf1f1f1f1;
+			return ptr;
+		}
+	} while (last != first);
+	return NULL;
+}
+
 void * delete_ptr_list_last(struct ptr_list **head)
 {
 	void *ptr = NULL;