io: io_never for events that should never happen.

[ccan] / ccan / io / io.h

diff --git a/ccan/io/io.h b/ccan/io/io.h
index bcdb11fdd0e0c1f1e9a08aac55a13e0afe888d92..478190f4d05b16def3f7eb481c2c8ecff334ee83 100644 (file)
--- a/ccan/io/io.h
+++ b/ccan/io/io.h
@@ -39,7 +39,8 @@ struct io_conn *io_new_conn_(int fd, struct io_plan plan);
  *
  * @finish will be called when an I/O operation fails, or you call
  * io_close() on the connection.  errno will be set to the value
  *
  * @finish will be called when an I/O operation fails, or you call
  * io_close() on the connection.  errno will be set to the value

- * after the failed I/O, or at the call to io_close().
+ * after the failed I/O, or at the call to io_close().  The fd
+ * will be closed (unless a duplex) before @finish is called.

  *
  * Example:
  * static void finish(struct io_conn *conn, void *unused)
  *
  * Example:
  * static void finish(struct io_conn *conn, void *unused)


@@ -489,6 +490,21 @@ bool io_is_idle(const struct io_conn *conn);
 #define io_break(ret, plan) (io_plan_no_debug(), io_break_((ret), (plan)))
 struct io_plan io_break_(void *ret, struct io_plan plan);
 
 #define io_break(ret, plan) (io_plan_no_debug(), io_break_((ret), (plan)))
 struct io_plan io_break_(void *ret, struct io_plan plan);
 

+/**
+ * io_never - assert if callback is called.
+ *
+ * Sometimes you want to make it clear that a callback should never happen
+ * (eg. for io_break).  This will assert() if called.
+ *
+ * Example:
+ * static struct io_plan break_out(struct io_conn *conn, void *unused)
+ * {
+ *     // We won't ever return from io_break
+ *     return io_break(conn, io_never());
+ * }
+ */
+struct io_plan io_never(void);
+

 /* FIXME: io_recvfrom/io_sendto */
 
 /**
 /* FIXME: io_recvfrom/io_sendto */
 
 /**