tal: make tal_len/tal_count(NULL) return 0.

[ccan] / ccan / tal / tal.h

diff --git a/ccan/tal/tal.h b/ccan/tal/tal.h
index bdaa3f67381ee2e93a1fb87c7a3746fe6fa69ac9..e525a01d1193144168d52c87ab901a1d9cbc655e 100644 (file)
--- a/ccan/tal/tal.h
+++ b/ccan/tal/tal.h
@@ -56,7 +56,8 @@ typedef void tal_t;
  * children (recursively) before finally freeing the memory.  It returns
  * NULL, for convenience.
  *
- * Note: errno is preserved by this call.
+ * Note: errno is preserved by this call, and also saved and restored
+ * for any destructors or notifiers.
  *
  * Example:
  *     p = tal_free(p);
@@ -168,6 +169,53 @@ void *tal_free(const tal_t *p);
 #define tal_del_destructor(ptr, function)                                    \
        tal_del_destructor_((ptr), typesafe_cb(void, void *, (function), (ptr)))
 
+/**
+ * tal_add_destructor2 - add a 2-arg callback function when context is destroyed.
+ * @ptr: The tal allocated object.
+ * @function: the function to call before it's freed.
+ * @arg: the extra argument to the function.
+ *
+ * Sometimes an extra argument is required for a destructor; this
+ * saves the extra argument internally to avoid the caller having to
+ * do an extra allocation.
+ *
+ * Note that this can only fail if your allocfn fails and your errorfn returns.
+ */
+#define tal_add_destructor2(ptr, function, arg)                                \
+       tal_add_destructor2_((ptr),                                     \
+                            typesafe_cb_cast(void (*)(tal_t *, void *), \
+                                             void (*)(__typeof__(ptr), \
+                                                      __typeof__(arg)), \
+                                             (function)),              \
+                            (arg))
+
+/**
+ * tal_del_destructor - remove a destructor callback function.
+ * @ptr: The tal allocated object.
+ * @function: the function to call before it's freed.
+ *
+ * If @function has not been successfully added as a destructor, this returns
+ * false.
+ */
+#define tal_del_destructor(ptr, function)                                    \
+       tal_del_destructor_((ptr), typesafe_cb(void, void *, (function), (ptr)))
+
+/**
+ * tal_del_destructor2 - remove 2-arg callback function.
+ * @ptr: The tal allocated object.
+ * @function: the function to call before it's freed.
+ * @arg: the extra argument to the function.
+ *
+ * If @function has not been successfully added as a destructor with
+ * @arg, this returns false.
+ */
+#define tal_del_destructor2(ptr, function, arg)                                \
+       tal_del_destructor2_((ptr),                                     \
+                            typesafe_cb_cast(void (*)(tal_t *, void *), \
+                                             void (*)(__typeof__(ptr), \
+                                                      __typeof__(arg)), \
+                                             (function)),              \
+                            (arg))
 enum tal_notify_type {
        TAL_NOTIFY_FREE = 1,
        TAL_NOTIFY_STEAL = 2,
@@ -194,6 +242,7 @@ enum tal_notify_type {
  * 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.
+ * errno is set to the value it was at the call of tal_free().
  *
  * TAL_NOTIFY_STEAL is called when @ptr's parent changes: @info is the
  * new parent.
@@ -232,7 +281,8 @@ enum tal_notify_type {
        tal_del_notifier_((ptr),                                        \
                          typesafe_cb_postargs(void, void *, (callback), \
                                               (ptr),                   \
-                                              enum tal_notify_type, void *))
+                                              enum tal_notify_type, void *), \
+                         false, NULL)
 
 /**
  * tal_set_name - attach a name to a tal pointer.
@@ -254,18 +304,18 @@ const char *tal_name(const tal_t *ptr);
 
 /**
  * tal_count - get the count of objects in a tal_arr.
- * @ptr: The tal allocated object array.
+ * @ptr: The tal allocated object array (or NULL)
  *
- * Returns 0 if @ptr has no length property, but be aware that that is
- * also a valid size!
+ * Returns 0 if @ptr has no length property or is NULL, but be aware
+ * that that is also a valid size!
  */
 #define tal_count(p) (tal_len(p) / sizeof(*p))
 
 /**
  * tal_len - get the count of bytes in a tal_arr.
- * @ptr: The tal allocated object array.
+ * @ptr: The tal allocated object array (or NULL)
  *
- * Returns 0 if @ptr has no length property, but be aware that that is
+ * Returns 0 if @ptr has no length property or NULL, but be aware that that is
  * also a valid size!
  */
 size_t tal_len(const tal_t *ptr);
@@ -285,7 +335,7 @@ tal_t *tal_first(const tal_t *root);
  * Returns NULL if there are no more immediate children.  This should be safe to
  * call on an altering tree unless @prev is no longer valid.
  */
-tal_t *tal_next(const const tal_t *prev);
+tal_t *tal_next(const tal_t *prev);
 
 /**
  * tal_parent - get the parent of a tal object.
@@ -447,12 +497,17 @@ bool tal_resize_(tal_t **ctxp, size_t size, size_t count, bool clear);
 bool tal_expand_(tal_t **ctxp, const void *src, size_t size, size_t count);
 
 bool tal_add_destructor_(const tal_t *ctx, void (*destroy)(void *me));
+bool tal_add_destructor2_(const tal_t *ctx, void (*destroy)(void *me, void *arg),
+                         void *arg);
 bool tal_del_destructor_(const tal_t *ctx, void (*destroy)(void *me));
+bool tal_del_destructor2_(const tal_t *ctx, void (*destroy)(void *me, void *arg),
+                         void *arg);
 
 bool tal_add_notifier_(const tal_t *ctx, enum tal_notify_type types,
                       void (*notify)(tal_t *ctx, enum tal_notify_type,
                                      void *info));
 bool tal_del_notifier_(const tal_t *ctx,
                       void (*notify)(tal_t *ctx, enum tal_notify_type,
-                                     void *info));
+                                     void *info),
+                      bool match_extra_arg, void *arg);
 #endif /* CCAN_TAL_H */