ccan/io: eliminate dir argument from io_wait and io_always.

We can use either empty slot for this, so figure it out internally.

This could cause problems if you want to use it with io_duplex, so
document that.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/io/_info

@@ -51,7 +51,7 @@
  *
  * 	// No room?  Wait for writer
  * 	if (b->end == sizeof(b->buf))
- * 		return io_wait(c, b, IO_IN, read_in, b);
+ * 		return io_wait(c, b, read_in, b);
  *
  * 	return io_read_partial(c, b->buf + b->end, sizeof(b->buf) - b->end,
  *			       &b->rlen, read_in, b);
@@ -71,7 +71,7 @@
  * 	if (b->end == b->start) {
  * 		if (b->finished)
  * 			return io_close(c);
- * 		return io_wait(c, b, IO_OUT, write_out, b);
+ * 		return io_wait(c, b, write_out, b);
  * 	}
  *
  * 	return io_write_partial(c, b->buf + b->start, b->end - b->start,

ccan/io/io.c

@@ -124,11 +124,17 @@ static struct io_plan *set_always(struct io_conn *conn,
 }
 
 struct io_plan *io_always_(struct io_conn *conn,
-			   enum io_direction dir,
 			   struct io_plan *(*next)(struct io_conn *, void *),
 			   void *arg)
 {
-	struct io_plan *plan = io_get_plan(conn, dir);
+	struct io_plan *plan;
+
+	/* If we're duplex, we want this on the current plan.  Otherwise,
+	 * doesn't matter. */
+	if (conn->plan[IO_IN].status == IO_UNSET)
+		plan = io_get_plan(conn, IO_IN);
+	else
+		plan = io_get_plan(conn, IO_OUT);
 
 	assert(next);
 	set_always(conn, plan, next, arg);
@@ -320,11 +326,18 @@ struct io_plan *io_connect_(struct io_conn *conn, const struct addrinfo *addr,
 }
 
 struct io_plan *io_wait_(struct io_conn *conn,
-			 const void *wait, enum io_direction dir,
+			 const void *wait,
 			 struct io_plan *(*next)(struct io_conn *, void *),
 			 void *arg)
 {
-	struct io_plan *plan = io_get_plan(conn, dir);
+	struct io_plan *plan;
+
+	/* If we're duplex, we want this on the current plan.  Otherwise,
+	 * doesn't matter. */
+	if (conn->plan[IO_IN].status == IO_UNSET)
+		plan = io_get_plan(conn, IO_IN);
+	else
+		plan = io_get_plan(conn, IO_OUT);
 
 	assert(next);
 
@@ -417,7 +430,7 @@ void io_break(const void *ret)
 
 struct io_plan *io_never(struct io_conn *conn)
 {
-	return io_always(conn, IO_IN, io_never_called, NULL);
+	return io_always(conn, io_never_called, NULL);
 }
 
 int io_conn_fd(const struct io_conn *conn)

ccan/io/io.h

@@ -6,11 +6,6 @@
 #include <stdbool.h>
 #include <unistd.h>
 
-enum io_direction {
-	IO_IN,
-	IO_OUT
-};
-
 /**
  * struct io_plan - a plan for input or output.
  *
@@ -340,7 +335,6 @@ struct io_plan *io_write_partial_(struct io_conn *conn,
 /**
  * io_always - plan to immediately call next callback
  * @conn: the connection that plan is for.
- * @dir: IO_IN or IO_OUT
  * @next: function to call.
  * @arg: @next argument
  *
@@ -352,16 +346,16 @@ struct io_plan *io_write_partial_(struct io_conn *conn,
  *						 void *unused)
  * {
  *	// Silly example: close on next time around loop.
- *	return io_always(conn, IO_IN, io_close_cb, NULL);
+ *	return io_always(conn, io_close_cb, NULL);
  * }
  */
-#define io_always(conn, dir, next, arg)					\
-	io_always_((conn), dir, typesafe_cb_preargs(struct io_plan *, void *, \
-						    (next), (arg),	\
-						    struct io_conn *),	\
+#define io_always(conn, next, arg)					\
+	io_always_((conn), typesafe_cb_preargs(struct io_plan *, void *, \
+					       (next), (arg),		\
+					       struct io_conn *),	\
 		   (arg))
 
-struct io_plan *io_always_(struct io_conn *conn, enum io_direction dir,
+struct io_plan *io_always_(struct io_conn *conn,
 			   struct io_plan *(*next)(struct io_conn *, void *),
 			   void *arg);
 
@@ -413,7 +407,6 @@ struct io_plan *io_connect_(struct io_conn *conn, const struct addrinfo *addr,
  * io_wait - leave a plan idle until something wakes us.
  * @conn: the connection that plan is for.
  * @waitaddr: the address to wait on.
- * @dir: IO_IN or IO_OUT
  * @next: function to call after waiting.
  * @arg: @next argument
  *
@@ -424,18 +417,18 @@ struct io_plan *io_connect_(struct io_conn *conn, const struct addrinfo *addr,
  * // Silly example to wait then close.
  * static struct io_plan *wait(struct io_conn *conn, void *b)
  * {
- *	return io_wait(conn, b, IO_IN, io_close_cb, NULL);
+ *	return io_wait(conn, b, io_close_cb, NULL);
  * }
  */
-#define io_wait(conn, waitaddr, dir, next, arg)				\
-	io_wait_((conn), (waitaddr), (dir),				\
+#define io_wait(conn, waitaddr, next, arg)				\
+	io_wait_((conn), (waitaddr),					\
 		 typesafe_cb_preargs(struct io_plan *, void *,		\
 				     (next), (arg),			\
 				     struct io_conn *),			\
 		 (arg))
 
 struct io_plan *io_wait_(struct io_conn *conn,
-			 const void *wait, enum io_direction dir,
+			 const void *wait,
 			 struct io_plan *(*next)(struct io_conn *, void *),
 			 void *arg);
 

ccan/io/io_plan.h

@@ -27,6 +27,11 @@ enum io_plan_status {
 	IO_CLOSING
 };
 
+enum io_direction {
+	IO_IN,
+	IO_OUT
+};
+
 /**
  * struct io_plan - one half of I/O to do
  * @status: the status of this plan.

ccan/io/test/run-06-idle.c

@@ -71,7 +71,7 @@ static struct io_plan *init_idle(struct io_conn *conn, struct data *d)
 	ok1(fd2 >= 0);
 	io_set_finish(io_new_conn(NULL, fd2, init_waker, d), finish_waker, d);
 
-	return io_wait(conn, d, IO_IN, read_buf, d);
+	return io_wait(conn, d, read_buf, d);
 }
 
 static int make_listen_fd(const char *port, struct addrinfo **info)

ccan/io/test/run-08-hangup-on-idle.c

@@ -15,7 +15,7 @@ static struct io_plan *read_in(struct io_conn *conn, char *buf)
 
 static struct io_plan *setup_waiter(struct io_conn *conn, char *buf)
 {
-	return io_wait(conn, buf, IO_IN, read_in, buf);
+	return io_wait(conn, buf, read_in, buf);
 }
 
 static struct io_plan *wake_and_close(struct io_conn *conn, char *buf)

ccan/io/test/run-08-read-after-hangup.c

@@ -27,7 +27,7 @@ static struct io_plan *init_writer(struct io_conn *conn, struct io_conn *wakeme)
 
 static struct io_plan *init_waiter(struct io_conn *conn, void *unused)
 {
-	return io_wait(conn, inbuf, IO_IN, read_buf, NULL);
+	return io_wait(conn, inbuf, read_buf, NULL);
 }
 
 int main(void)

ccan/io/test/run-10-many.c

@@ -34,7 +34,7 @@ static struct io_plan *poke_writer(struct io_conn *conn, struct buffer *buf)
 	io_wake(&buf->writer);
 
 	/* I'll wait until you wake me. */
-	return io_wait(conn, &buf->reader, IO_IN, read_buf, buf);
+	return io_wait(conn, &buf->reader, read_buf, buf);
 }
 
 static struct io_plan *write_buf(struct io_conn *conn, struct buffer *buf)
@@ -52,12 +52,12 @@ static struct io_plan *poke_reader(struct io_conn *conn, struct buffer *buf)
 		return io_close(conn);
 
 	/* I'll wait until you tell me to write. */
-	return io_wait(conn, &buf->writer, IO_OUT, write_buf, buf);
+	return io_wait(conn, &buf->writer, write_buf, buf);
 }
 
 static struct io_plan *setup_reader(struct io_conn *conn, struct buffer *buf)
 {
-	return io_wait(conn, &buf->reader, IO_IN, read_buf, buf);
+	return io_wait(conn, &buf->reader, read_buf, buf);
 }
 
 static struct buffer buf[NUM];

ccan/io/test/run-13-all-idle.c

@@ -9,7 +9,7 @@
 
 static struct io_plan *setup_waiter(struct io_conn *conn, int *status)
 {
-	return io_wait(conn, status, IO_IN, io_close_cb, NULL);
+	return io_wait(conn, status, io_close_cb, NULL);
 }
 
 int main(void)