io: add io_is_idle().

[ccan] / ccan / io / io.h

diff --git a/ccan/io/io.h b/ccan/io/io.h
index 0318aef300873fa71104e0a2b630ad28e93e7065..df0764bd17e1ff7f50633ffe91a45de4c02c6a22 100644 (file)
--- a/ccan/io/io.h
+++ b/ccan/io/io.h
@@ -431,6 +431,21 @@ struct io_conn *io_duplex_(struct io_conn *conn, struct io_plan plan);
 #define io_wake(conn, plan) (io_plan_no_debug(), io_wake_((conn), (plan)))
 void io_wake_(struct io_conn *conn, struct io_plan plan);
 
+/**
+ * io_is_idle - is a connection idle?
+ *
+ * This can be useful for complex protocols, eg. where you want a connection
+ * to send something, so you queue it and wake it if it's idle.
+ *
+ * Example:
+ *     struct io_conn *sleeper;
+ *     sleeper = io_new_conn(open("/dev/null", O_RDONLY), io_idle());
+ *
+ *     assert(io_is_idle(sleeper));
+ *     io_wake(sleeper, io_write("junk", 4, io_close_cb, NULL));
+ */
+bool io_is_idle(const struct io_conn *conn);
+
 /**
  * io_break - return from io_loop()
  * @ret: non-NULL value to return from io_loop().