talloc_link; a replacement for talloc's references.

[ccan] / ccan / talloc_link / talloc_link.c

diff --git a/ccan/talloc_link/talloc_link.c b/ccan/talloc_link/talloc_link.c
new file mode 100644 (file)
index 0000000..b72b436
--- /dev/null
+++ b/ccan/talloc_link/talloc_link.c
@@ -0,0 +1,95 @@
+#include <ccan/list/list.h>
+#include <ccan/talloc/talloc.h>
+#include <ccan/talloc_link/talloc_link.h>
+#include <assert.h>
+
+/* Fake parent, if they care. */
+static void *talloc_links = NULL;
+
+/* This is the parent of the linked object, so we can implement delink. */
+struct talloc_linked {
+       struct list_head links;
+       const void *obj;
+};
+
+/* This is a child of the linker, but not a parent of ref. */
+struct talloc_link {
+       struct list_node list;
+       struct talloc_linked *linked;
+};
+
+static int destroy_link(struct talloc_link *link)
+{
+       list_del(&link->list);
+       if (list_empty(&link->linked->links))
+               talloc_free(link->linked);
+       return 0;
+}
+
+static bool add_link(const void *ctx, struct talloc_linked *linked)
+{
+       struct talloc_link *link = talloc(ctx, struct talloc_link);
+       if (!link)
+               return false;
+
+       link->linked = linked;
+       list_add(&linked->links, &link->list);
+       talloc_set_destructor(link, destroy_link);
+       return true;
+}
+
+void *_talloc_linked(const void *ctx, const void *newobj)
+{
+       struct talloc_linked *linked;
+
+       if (talloc_parent(newobj)) {
+               /* Assume leak reporting is on: create dummy parent. */
+               if (!talloc_links)
+                       talloc_links = talloc_named_const(NULL, 0,
+                                                         "talloc_links");
+               /* This should now have same pseudo-NULL parent. */
+               assert(talloc_parent(newobj) == talloc_parent(talloc_links));
+       }
+
+       linked = talloc(talloc_links, struct talloc_linked);
+       if (!linked) {
+               talloc_free(newobj);
+               return NULL;
+       }
+       list_head_init(&linked->links);
+       linked->obj = talloc_steal(linked, newobj);
+
+       if (!add_link(ctx, linked)) {
+               talloc_free(linked);
+               return NULL;
+       }
+
+       return (void *)newobj;
+}
+
+void *_talloc_link(const void *ctx, const void *obj)
+{
+       struct talloc_linked *linked;
+
+       linked = talloc_get_type(talloc_parent(obj), struct talloc_linked);
+       assert(!list_empty(&linked->links));
+       return add_link(ctx, linked) ? (void *)obj : NULL;
+}
+
+void talloc_delink(const void *ctx, const void *obj)
+{
+       struct talloc_linked *linked;
+       struct talloc_link *i;
+
+       if (!obj)
+               return;
+
+       linked = talloc_get_type(talloc_parent(obj), struct talloc_linked);
+       list_for_each(&linked->links, i, list) {
+               if (talloc_is_parent(i, ctx)) {
+                       talloc_free(i);
+                       return;
+               }
+       }
+       abort();
+}