tal: add general notifiers.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/tal/tal.c

@@ -18,6 +18,7 @@ enum prop_type {
 	CHILDREN = 0x00c1d500,
 	DESTRUCTOR = 0x00de5700,
 	NAME = 0x00111100,
+	NOTIFIER = 0x00071f00
 };
 
 struct tal_hdr {
@@ -47,6 +48,12 @@ struct name {
 	char name[];
 };
 
+struct notifier {
+	struct prop_hdr hdr; /* NOTIFIER */
+	enum tal_notify_type types;
+	void (*notifyfn)(tal_t *, enum tal_notify_type, void *);
+};
+
 static struct {
 	struct tal_hdr hdr;
 	struct children c;
@@ -169,9 +176,9 @@ static struct tal_hdr *to_tal_hdr_or_null(const void *ctx)
 	return to_tal_hdr(ctx);
 }
 
-static void *from_tal_hdr(struct tal_hdr *hdr)
+static void *from_tal_hdr(const struct tal_hdr *hdr)
 {
-	return hdr + 1;
+	return (void *)(hdr + 1);
 }
 
 #ifdef TAL_DEBUG
@@ -194,6 +201,24 @@ static struct tal_hdr *debug_tal(struct tal_hdr *tal)
 }
 #endif
 
+static void notify(const struct tal_hdr *ctx,
+		   enum tal_notify_type type, const void *info)
+{
+        const struct prop_hdr *p;
+
+        for (p = ctx->prop; p; p = p->next) {
+		struct notifier *n;
+
+                if (is_literal(p))
+			break;
+                if (p->type != NOTIFIER)
+			continue;
+		n = (struct notifier *)p;
+		if (n->types & type)
+			n->notifyfn(from_tal_hdr(ctx), type, (void *)info);
+	}
+}
+
 static void *allocate(size_t size)
 {
 	void *ret;
@@ -280,6 +305,44 @@ static bool del_destructor_property(struct tal_hdr *t,
         return false;
 }
 
+static struct notifier *add_notifier_property(struct tal_hdr *t,
+					      enum tal_notify_type types,
+					      void (*fn)(void *,
+							 enum tal_notify_type,
+							 void *))
+{
+	struct notifier *prop = allocate(sizeof(*prop));
+	if (prop) {
+		init_property(&prop->hdr, t, NOTIFIER);
+		prop->types = types;
+		prop->notifyfn = fn;
+	}
+	return prop;
+}
+
+static bool del_notifier_property(struct tal_hdr *t,
+				  void (*fn)(tal_t *,
+					     enum tal_notify_type, void *))
+{
+        struct prop_hdr **p;
+
+        for (p = (struct prop_hdr **)&t->prop; *p; p = &(*p)->next) {
+		struct notifier *n;
+
+                if (is_literal(*p))
+			break;
+                if ((*p)->type != NOTIFIER)
+			continue;
+		n = (struct notifier *)*p;
+		if (n->notifyfn == fn) {
+			*p = (*p)->next;
+			freefn(n);
+			return true;
+		}
+        }
+        return false;
+}
+
 static struct name *add_name_property(struct tal_hdr *t, const char *name)
 {
 	struct name *prop;
@@ -323,7 +386,7 @@ static bool add_child(struct tal_hdr *parent, struct tal_hdr *child)
 	return true;
 }
 
-static void del_tree(struct tal_hdr *t)
+static void del_tree(struct tal_hdr *t, const tal_t *orig)
 {
 	struct prop_hdr **prop, *p, *next;
 
@@ -341,6 +404,9 @@ static void del_tree(struct tal_hdr *t)
 		freefn(d);
         }
 
+	/* Call free notifiers. */
+	notify(t, TAL_NOTIFY_FREE, (tal_t *)orig);
+
 	/* Now free children and groups. */
 	prop = find_property_ptr(t, CHILDREN);
 	if (prop) {
@@ -349,7 +415,7 @@ static void del_tree(struct tal_hdr *t)
 
 		while ((i = list_top(&c->children, struct tal_hdr, list))) {
 			list_del(&i->list);
-			del_tree(i);
+			del_tree(i, orig);
 		}
 	}
 
@@ -376,6 +442,7 @@ void *tal_alloc_(const tal_t *ctx, size_t size, bool clear, const char *label)
 		return NULL;
 	}
 	debug_tal(parent);
+	notify(parent, TAL_NOTIFY_ADD_CHILD, from_tal_hdr(debug_tal(child)));
 	return from_tal_hdr(debug_tal(child));
 }
 
@@ -385,8 +452,10 @@ void *tal_free(const tal_t *ctx)
 		struct tal_hdr *t;
 		int saved_errno = errno;
 		t = debug_tal(to_tal_hdr(ctx));
+		notify(ignore_destroying_bit(t->parent_child)->parent,
+		       TAL_NOTIFY_DEL_CHILD, ctx);
 		list_del(&t->list);
-		del_tree(t);
+		del_tree(t, ctx);
 		errno = saved_errno;
 	}
 	return NULL;
@@ -412,18 +481,56 @@ void *tal_steal_(const tal_t *new_parent, const tal_t *ctx)
 			return NULL;
 		}
 		debug_tal(newpar);
+		notify(t, TAL_NOTIFY_STEAL, new_parent);
         }
         return (void *)ctx;
 }
 
 bool tal_add_destructor_(tal_t *ctx, void (*destroy)(void *me))
 {
-        return add_destructor_property(debug_tal(to_tal_hdr(ctx)), destroy);
+	tal_t *t = debug_tal(to_tal_hdr(ctx));
+        return add_destructor_property(t, destroy);
+}
+
+bool tal_add_notifier_(tal_t *ctx, enum tal_notify_type types,
+		       void (*callback)(tal_t *, enum tal_notify_type, void *))
+{
+	tal_t *t = debug_tal(to_tal_hdr(ctx));
+	struct notifier *n;
+
+	assert(types);
+	assert((types & ~(TAL_NOTIFY_FREE | TAL_NOTIFY_STEAL | TAL_NOTIFY_MOVE
+			  | TAL_NOTIFY_RESIZE | TAL_NOTIFY_RENAME
+			  | TAL_NOTIFY_ADD_CHILD | TAL_NOTIFY_DEL_CHILD
+			  | TAL_NOTIFY_ADD_NOTIFIER
+			  | TAL_NOTIFY_DEL_NOTIFIER)) == 0);
+
+	/* Don't call notifier about itself: set types after! */
+        n = add_notifier_property(t, 0, callback);
+	if (unlikely(!n))
+		return false;
+
+	notify(t, TAL_NOTIFY_ADD_NOTIFIER, callback);
+	n->types = types;
+	return true;
+}
+
+bool tal_del_notifier_(tal_t *ctx,
+		       void (*callback)(tal_t *, enum tal_notify_type, void *))
+{
+	struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
+	bool ret;
+
+        ret = del_notifier_property(t, callback);
+	if (ret)
+		notify(t, TAL_NOTIFY_DEL_NOTIFIER, callback);
+	return ret;
 }
 
 bool tal_del_destructor_(tal_t *ctx, void (*destroy)(void *me))
 {
-        return del_destructor_property(debug_tal(to_tal_hdr(ctx)), destroy);
+	struct tal_hdr *t = debug_tal(to_tal_hdr(ctx));
+        return del_destructor_property(t, destroy);
 }
 
 bool tal_set_name_(tal_t *ctx, const char *name, bool literal)
@@ -448,11 +555,11 @@ bool tal_set_name_(tal_t *ctx, const char *name, bool literal)
                 /* Append literal. */
                 for (p = &t->prop; *p && !is_literal(*p); p = &(*p)->next);
                 *p = (struct prop_hdr *)name;
-                return true;
-        }
-        if (!add_name_property(t, name))
+        } else if (!add_name_property(t, name))
 		return false;
+
 	debug_tal(t);
+	notify(t, TAL_NOTIFY_RENAME, name);
 	return true;
 }
 
@@ -551,21 +658,24 @@ bool tal_resize_(tal_t **ctxp, size_t size)
 	}
 
 	/* If it didn't move, we're done! */
-        if (t == old_t)
-                return true;
-	update_bounds(t, size + sizeof(struct tal_hdr));
-
-	/* Fix up linked list pointers. */
-	if (list_entry(t->list.next, struct tal_hdr, list) != old_t)
-		t->list.next->prev = t->list.prev->next = &t->list;
-
-	/* Fix up child property's parent pointer. */
-	child = find_property(t, CHILDREN);
-	if (child) {
-		assert(child->parent == old_t);
-		child->parent = t;
+        if (t != old_t) {
+		update_bounds(t, size + sizeof(struct tal_hdr));
+
+		/* Fix up linked list pointers. */
+		if (list_entry(t->list.next, struct tal_hdr, list) != old_t)
+			t->list.next->prev = t->list.prev->next = &t->list;
+
+		/* Fix up child property's parent pointer. */
+		child = find_property(t, CHILDREN);
+		if (child) {
+			assert(child->parent == old_t);
+			child->parent = t;
+		}
+		*ctxp = from_tal_hdr(debug_tal(t));
+		notify(t, TAL_NOTIFY_MOVE, from_tal_hdr(old_t));
 	}
-	*ctxp = from_tal_hdr(debug_tal(t));
+	notify(t, TAL_NOTIFY_RESIZE, (void *)size);
+
 	return true;
 }
 
@@ -691,6 +801,7 @@ static void dump_node(unsigned int indent, const struct tal_hdr *t)
 		struct children *c;
 		struct destructor *d;
 		struct name *n;
+		struct notifier *no;
                 if (is_literal(p)) {
 			printf(" \"%s\"", (const char *)p);
 			break;
@@ -710,6 +821,10 @@ static void dump_node(unsigned int indent, const struct tal_hdr *t)
 			n = (struct name *)p;
 			printf(" NAME(%p):%s", p, n->name);
 			break;
+		case NOTIFIER:
+			no = (struct notifier *)p;
+			printf(" NOTIFIER(%p):fn=%p", p, no->notifyfn);
+			break;
 		default:
 			printf(" **UNKNOWN(%p):%i**", p, p->type);
 		}
@@ -784,6 +899,7 @@ static bool check_node(struct children *parent_child,
 			children = (struct children *)p;
 			break;
 		case DESTRUCTOR:
+		case NOTIFIER:
 			break;
 		case NAME:
 			if (name)

ccan/tal/tal.h

@@ -126,6 +126,8 @@ void *tal_free(const tal_t *p);
  * tal_add_destructor - add a callback function when this context is destroyed.
  * @ptr: The tal allocated object.
  * @function: the function to call before it's freed.
+ *
+ * Note that this can only fail if your allocfn fails and your errorfn returns.
  */
 #define tal_add_destructor(ptr, function)				      \
 	tal_add_destructor_((ptr), typesafe_cb(void, void *, (function), (ptr)))
@@ -141,6 +143,71 @@ void *tal_free(const tal_t *p);
 #define tal_del_destructor(ptr, function)				      \
 	tal_del_destructor_((ptr), typesafe_cb(void, void *, (function), (ptr)))
 
+enum tal_notify_type {
+	TAL_NOTIFY_FREE = 1,
+	TAL_NOTIFY_STEAL = 2,
+	TAL_NOTIFY_MOVE = 4,
+	TAL_NOTIFY_RESIZE = 8,
+	TAL_NOTIFY_RENAME = 16,
+	TAL_NOTIFY_ADD_CHILD = 32,
+	TAL_NOTIFY_DEL_CHILD = 64,
+	TAL_NOTIFY_ADD_NOTIFIER = 128,
+	TAL_NOTIFY_DEL_NOTIFIER = 256
+};
+
+/**
+ * tal_add_notifier - add a callback function when this context changes.
+ * @ptr: The tal allocated object.
+ * @types: Bitwise OR of the types the callback is interested in.
+ * @callback: the function to call.
+ *
+ * Note that this can only fail if your allocfn fails and your errorfn
+ * returns.  Also note that notifiers are not reliable in the case
+ * where an allocation fails, as they may be called before any
+ * allocation is actually done.
+ *
+ * TAL_NOTIFY_FREE is called when @ptr is freed, either directly or
+ * because an ancestor is freed: @info is the argument to tal_free().
+ * It is exactly equivalent to a destructor, with more information.
+ *
+ * TAL_NOTIFY_STEAL is called when @ptr's parent changes: @info is the
+ * new parent.
+ *
+ * TAL_NOTIFY_MOVE is called when @ptr is realloced (via tal_resize)
+ * and moved.  In this case, @ptr arg here is the new memory, and
+ * @info is the old pointer.
+ *
+ * TAL_NOTIFY_RESIZE is called when @ptr is realloced via tal_resize:
+ * @info is the new size, in bytes.  If the pointer has moved,
+ * TAL_NOTIFY_MOVE callbacks are called first.
+ *
+ * TAL_NOTIFY_ADD_CHILD/TAL_NOTIFY_DEL_CHILD are called when @ptr is
+ * the context for a tal() allocating call, or a direct child is
+ * tal_free()d: @info is the child.  Note that TAL_NOTIFY_DEL_CHILD is
+ * not called when this context is tal_free()d: TAL_NOTIFY_FREE is
+ * considered sufficient for that case.
+ *
+ * TAL_NOTIFY_ADD_NOTIFIER/TAL_NOTIFIER_DEL_NOTIFIER are called when
+ * a notifier is added or removed (not for this notifier): @info is the
+ * callback.
+ */
+#define tal_add_notifier(ptr, types, callback)				\
+	tal_add_notifier_((ptr), (types),				\
+			  typesafe_cb_postargs(void, tal_t *, (callback), \
+					       (ptr),			\
+					       enum tal_notify_type, void *))
+
+/**
+ * tal_del_notifier - remove a notifier callback function.
+ * @ptr: The tal allocated object.
+ * @callback: the function to call.
+ */
+#define tal_del_notifier(ptr, callback)					\
+	tal_del_notifier_((ptr),					\
+			  typesafe_cb_postargs(void, void *, (callback), \
+					       (ptr),			\
+					       enum tal_notify_type, void *))
+
 /**
  * tal_set_name - attach a name to a tal pointer.
  * @ptr: The tal allocated object.
@@ -337,4 +404,10 @@ bool tal_resize_(tal_t **ctxp, size_t size);
 bool tal_add_destructor_(tal_t *ctx, void (*destroy)(void *me));
 bool tal_del_destructor_(tal_t *ctx, void (*destroy)(void *me));
 
+bool tal_add_notifier_(tal_t *ctx, enum tal_notify_type types,
+		       void (*notify)(tal_t *ctx, enum tal_notify_type,
+				      void *info));
+bool tal_del_notifier_(tal_t *ctx,
+		       void (*notify)(tal_t *ctx, enum tal_notify_type,
+				      void *info));
 #endif /* CCAN_TAL_H */

ccan/tal/test/run-notifier.c

@@ -0,0 +1,130 @@
+#include <ccan/tal/tal.h>
+#include <ccan/tal/tal.c>
+#include <ccan/tap/tap.h>
+
+static enum tal_notify_type expect;
+static void *expect_info;
+static char *ctx;
+static unsigned int notified1, notified2;
+
+/* Make sure we always move on resize. */
+static void *my_realloc(void *old, size_t size)
+{
+	void *new = realloc(old, size);
+	if (new == old) {
+		void *p = malloc(size);
+		memcpy(p, old, size);
+		free(old);
+		new = p;
+	}
+	return new;
+}
+
+static void notify1(char *p, enum tal_notify_type notify, void *info)
+{
+	ok1(ctx == ctx);
+	ok1(notify == expect);
+	if (expect_info == &expect_info)
+		expect_info = info;
+	else
+		ok1(info == expect_info);
+	notified1++;
+}
+
+static void notify2(char *ctx, enum tal_notify_type notify, void *info)
+{
+	notified2++;
+}
+
+static bool seen_move, seen_resize;
+static void resize_notifier(char *p, enum tal_notify_type notify, void *info)
+{
+	if (notify == TAL_NOTIFY_MOVE) {
+		ok1(!seen_move);
+		ok1(!seen_resize);
+		ok1(info == ctx);
+		ok1(p != ctx);
+		ctx = p;
+		seen_move = true;
+	} else if (notify == TAL_NOTIFY_RESIZE) {
+		ok1(!seen_resize);
+		ok1(seen_move);
+		ok1(p == ctx);
+		ok1((size_t)info == 100);
+		seen_resize = true;
+	} else
+		fail("Unexpected notifier %i", notify);
+}
+
+int main(void)
+{
+	char *child, *new_ctx;
+
+	plan_tests(56);
+
+	ctx = tal(NULL, char);
+	ok1(tal_add_notifier(ctx, 511, notify1));
+	ok1(notified1 == 0);
+	ok1(notified2 == 0);
+
+	expect = TAL_NOTIFY_STEAL;
+	expect_info = NULL;
+	ok1(tal_steal(NULL, ctx) == ctx);
+	ok1(notified1 == 1);
+
+	expect = TAL_NOTIFY_ADD_NOTIFIER;
+	expect_info = notify2;
+	ok1(tal_add_notifier(ctx, TAL_NOTIFY_RENAME|TAL_NOTIFY_ADD_NOTIFIER
+			     |TAL_NOTIFY_DEL_NOTIFIER, notify2));
+	ok1(notified1 == 2);
+	ok1(notified2 == 0);
+
+	expect = TAL_NOTIFY_RENAME;
+	expect_info = (char *)"newname";
+	ok1(tal_set_name(ctx, (char *)expect_info));
+	ok1(notified1 == 3);
+	ok1(notified2 == 1);
+
+	expect = TAL_NOTIFY_DEL_NOTIFIER;
+	expect_info = notify2;
+	ok1(tal_del_notifier(ctx, notify2));
+	ok1(notified1 == 4);
+	ok1(notified2 == 1);
+
+	/* Failed delete should not call notifier! */
+	expect = TAL_NOTIFY_DEL_NOTIFIER;
+	expect_info = notify2;
+	ok1(!tal_del_notifier(ctx, notify2));
+	ok1(notified1 == 4);
+	ok1(notified2 == 1);
+
+	expect = TAL_NOTIFY_ADD_CHILD;
+	expect_info = &expect_info;
+	child = tal(ctx, char);
+	ok1(notified1 == 5);
+	ok1(notified2 == 1);
+	ok1(expect_info == child);
+
+	expect = TAL_NOTIFY_DEL_CHILD;
+	expect_info = child;
+	tal_free(child);
+	ok1(notified1 == 6);
+	ok1(notified2 == 1);
+
+	expect = TAL_NOTIFY_FREE;
+	expect_info = ctx;
+	tal_free(ctx);
+	ok1(notified1 == 7);
+	ok1(notified2 == 1);
+
+	tal_set_backend(NULL, my_realloc, NULL, NULL);
+	ctx = new_ctx = tal(NULL, char);
+	ok1(tal_add_notifier(new_ctx, 511, resize_notifier));
+	ok1(tal_resize(&new_ctx, 100));
+	ok1(seen_move);
+	ok1(seen_resize);
+	tal_del_notifier(new_ctx, resize_notifier);
+	tal_free(new_ctx);
+
+	return exit_status();
+}