From: Rusty Russell <rusty@rustcorp.com.au>
Date: Mon, 14 Oct 2013 10:58:35 +0000 (+1030)
Subject: ccan/io: pass struct io_plan explicitly.
X-Git-Url: http://git.ozlabs.org/?p=ccan;a=commitdiff_plain;h=625bae8f5720d3ad3253ea9b26ad68abcd81bde5

ccan/io: pass struct io_plan explicitly.

This simplifies some things: in particular, we can construct an
io_plan without needing the current io_conn.

On the other hand, we need to expose the structure now.

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

diff --git a/ccan/io/_info b/ccan/io/_info
index affd97b4..e7dfe9da 100644
--- a/ccan/io/_info
+++ b/ccan/io/_info
@@ -32,18 +32,18 @@
  * };
  *
  * // This reads from stdin.
- * static struct io_plan *wake_writer(struct io_conn *, struct stdin_buffer *);
+ * static struct io_plan wake_writer(struct io_conn *, struct stdin_buffer *);
  * // This writes the stdin buffer to the child.
- * static struct io_plan *write_to_child(struct io_conn *c,
- *					 struct stdin_buffer *b);
- * static struct io_plan *read_stdin(struct io_conn *c, struct stdin_buffer *b)
+ * static struct io_plan write_to_child(struct io_conn *c,
+ *					struct stdin_buffer *b);
+ * static struct io_plan read_stdin(struct io_conn *c, struct stdin_buffer *b)
  * {
  * 	assert(c == b->reader);
  * 	b->len = sizeof(b->inbuf);
  * 	return io_read_partial(c, b->inbuf, &b->len, wake_writer, b);
  * }
  *
- * static struct io_plan *wake_writer(struct io_conn *c, struct stdin_buffer *b)
+ * static struct io_plan wake_writer(struct io_conn *c, struct stdin_buffer *b)
  * {
  * 	assert(c == b->reader);
  * 	io_wake(b->writer, write_to_child, b);
@@ -57,14 +57,14 @@
  * 	b->reader = NULL;
  * }
  *
- * static struct io_plan *wake_reader(struct io_conn *c, struct stdin_buffer *b)
+ * static struct io_plan wake_reader(struct io_conn *c, struct stdin_buffer *b)
  * {
  * 	assert(c == b->writer);
  * 	io_wake(b->reader, read_stdin, b);
  * 	return io_idle(c);
  * }
  *
- * static struct io_plan *write_to_child(struct io_conn *conn,
+ * static struct io_plan write_to_child(struct io_conn *conn,
  * 				        struct stdin_buffer *b)
  * {
  * 	assert(conn == b->writer);
@@ -73,8 +73,8 @@
  * 	return io_write(conn, b->inbuf, b->len, wake_reader, b);
  * }
  *
- * static struct io_plan *start_writer(struct io_conn *conn,
- * 				       struct stdin_buffer *b)
+ * static struct io_plan start_writer(struct io_conn *conn,
+ * 				      struct stdin_buffer *b)
  * {
  * 	assert(conn == b->writer);
  * 	return io_idle(conn);
@@ -87,8 +87,8 @@
  * }
  *
  * // This reads from the child and saves it into buffer.
- * static struct io_plan *read_from_child(struct io_conn *conn,
- *					  struct buffer *b)
+ * static struct io_plan read_from_child(struct io_conn *conn,
+ *					 struct buffer *b)
  * {
  * 	b->off += b->rlen;
  *
diff --git a/ccan/io/backend.h b/ccan/io/backend.h
index 765e920e..c03ce2dc 100644
--- a/ccan/io/backend.h
+++ b/ccan/io/backend.h
@@ -10,60 +10,21 @@ struct fd {
 	size_t backend_info;
 };
 
-
 /* Listeners create connections. */
 struct io_listener {
 	struct fd fd;
 
 	/* These are for connections we create. */
-	struct io_plan *(*next)(struct io_conn *, void *arg);
+	struct io_plan (*next)(struct io_conn *, void *arg);
 	void (*finish)(struct io_conn *, void *arg);
 	void *conn_arg;
 };
 
-enum io_result {
-	RESULT_AGAIN,
-	RESULT_FINISHED,
-	RESULT_CLOSE
-};
-
-enum io_state {
-	IO_IO,
-	IO_NEXT, /* eg starting, woken from idle, return from io_break. */
-	IO_IDLE,
-	IO_FINISHED
-};
-
-static inline enum io_state from_ioplan(struct io_plan *op)
-{
-	return (enum io_state)(long)op;
-}
-
-struct io_state_read {
-	char *buf;
-	size_t len;
-};
-
-struct io_state_write {
-	const char *buf;
-	size_t len;
-};
-
-struct io_state_readpart {
-	char *buf;
-	size_t *lenp;
-};
-
-struct io_state_writepart {
-	const char *buf;
-	size_t *lenp;
-};
-
 struct io_timeout {
 	struct timer timer;
 	struct io_conn *conn;
 
-	struct io_plan *(*next)(struct io_conn *, void *arg);
+	struct io_plan (*next)(struct io_conn *, void *arg);
 	void *next_arg;
 };
 
@@ -71,25 +32,13 @@ struct io_timeout {
 struct io_conn {
 	struct fd fd;
 
-	struct io_plan *(*next)(struct io_conn *, void *arg);
-	void *next_arg;
-
 	void (*finish)(struct io_conn *, void *arg);
 	void *finish_arg;
 
 	struct io_conn *duplex;
 	struct io_timeout *timeout;
 
-	enum io_result (*io)(struct io_conn *conn);
-
-	int pollflag; /* 0, POLLIN or POLLOUT */
-	enum io_state state;
-	union {
-		struct io_state_read read;
-		struct io_state_write write;
-		struct io_state_readpart readpart;
-		struct io_state_writepart writepart;
-	} u;
+	struct io_plan plan;
 };
 
 static inline bool timeout_active(const struct io_conn *conn)
@@ -107,5 +56,5 @@ void backend_wakeup(struct io_conn *conn);
 void backend_add_timeout(struct io_conn *conn, struct timespec ts);
 void backend_del_timeout(struct io_conn *conn);
 
-struct io_plan *do_ready(struct io_conn *conn);
+struct io_plan do_ready(struct io_conn *conn);
 #endif /* CCAN_IO_BACKEND_H */
diff --git a/ccan/io/benchmarks/run-different-speed.c b/ccan/io/benchmarks/run-different-speed.c
index 10fa0b96..537a67bb 100644
--- a/ccan/io/benchmarks/run-different-speed.c
+++ b/ccan/io/benchmarks/run-different-speed.c
@@ -25,21 +25,21 @@ struct client {
 	char reply_buffer[REPLY_SIZE];
 };
 
-static struct io_plan *write_reply(struct io_conn *conn, struct client *client);
-static struct io_plan *read_request(struct io_conn *conn, struct client *client)
+static struct io_plan write_reply(struct io_conn *conn, struct client *client);
+static struct io_plan read_request(struct io_conn *conn, struct client *client)
 {
 	return io_read(conn, client->request_buffer, REQUEST_SIZE,
 		       write_reply, client);
 }
 
 /* once we're done, loop again. */
-static struct io_plan *write_complete(struct io_conn *conn, struct client *client)
+static struct io_plan write_complete(struct io_conn *conn, struct client *client)
 {
 	completed++;
 	return read_request(conn, client);
 }
 
-static struct io_plan *write_reply(struct io_conn *conn, struct client *client)
+static struct io_plan write_reply(struct io_conn *conn, struct client *client)
 {
 	return io_write(conn, client->reply_buffer, REPLY_SIZE,
 			write_complete, client);
@@ -106,12 +106,12 @@ static void sigalarm(int sig)
 	write(timeout[1], "1", 1);
 }
 
-static struct io_plan *do_timeout(struct io_conn *conn, char *buf)
+static struct io_plan do_timeout(struct io_conn *conn, char *buf)
 {
 	return io_break(conn, buf, NULL, NULL);
 }
 
-static struct io_plan *do_timeout_read(struct io_conn *conn, char *buf)
+static struct io_plan do_timeout_read(struct io_conn *conn, char *buf)
 {
 	return io_read(conn, buf, 1, do_timeout, buf);
 }
diff --git a/ccan/io/benchmarks/run-length-prefix.c b/ccan/io/benchmarks/run-length-prefix.c
index 74290fd8..2ed9c729 100644
--- a/ccan/io/benchmarks/run-length-prefix.c
+++ b/ccan/io/benchmarks/run-length-prefix.c
@@ -25,28 +25,28 @@ struct client {
 	char *request_buffer;
 };
 
-static struct io_plan *write_reply(struct io_conn *conn, struct client *client);
-static struct io_plan *read_body(struct io_conn *conn, struct client *client)
+static struct io_plan write_reply(struct io_conn *conn, struct client *client);
+static struct io_plan read_body(struct io_conn *conn, struct client *client)
 {
 	assert(client->len <= REQUEST_MAX);
 	return io_read(conn, client->request_buffer, client->len,
 		       write_reply, client);
 }
 
-static struct io_plan *read_header(struct io_conn *conn, struct client *client)
+static struct io_plan read_header(struct io_conn *conn, struct client *client)
 {
 	return io_read(conn, &client->len, sizeof(client->len),
 		       read_body, client);
 }
 
 /* once we're done, loop again. */
-static struct io_plan *write_complete(struct io_conn *conn, struct client *client)
+static struct io_plan write_complete(struct io_conn *conn, struct client *client)
 {
 	completed++;
 	return read_header(conn, client);
 }
 
-static struct io_plan *write_reply(struct io_conn *conn, struct client *client)
+static struct io_plan write_reply(struct io_conn *conn, struct client *client)
 {
 	return io_write(conn, &client->len, sizeof(client->len),
 			write_complete, client);
@@ -112,12 +112,12 @@ static void sigalarm(int sig)
 	write(timeout[1], "1", 1);
 }
 
-static struct io_plan *do_timeout(struct io_conn *conn, char *buf)
+static struct io_plan do_timeout(struct io_conn *conn, char *buf)
 {
 	return io_break(conn, buf, NULL, NULL);
 }
 
-static struct io_plan *do_timeout_read(struct io_conn *conn, char *buf)
+static struct io_plan do_timeout_read(struct io_conn *conn, char *buf)
 {
 	return io_read(conn, buf, 1, do_timeout, buf);
 }
diff --git a/ccan/io/benchmarks/run-loop.c b/ccan/io/benchmarks/run-loop.c
index 5dc1c3e1..a2898e13 100644
--- a/ccan/io/benchmarks/run-loop.c
+++ b/ccan/io/benchmarks/run-loop.c
@@ -16,24 +16,24 @@ struct buffer {
 	char buf[32];
 };
 
-static struct io_plan *poke_writer(struct io_conn *conn, struct buffer *buf);
-static struct io_plan *poke_reader(struct io_conn *conn, struct buffer *buf);
+static struct io_plan poke_writer(struct io_conn *conn, struct buffer *buf);
+static struct io_plan poke_reader(struct io_conn *conn, struct buffer *buf);
 
-static struct io_plan *do_read(struct io_conn *conn, struct buffer *buf)
+static struct io_plan do_read(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->reader);
 
 	return io_read(conn, &buf->buf, sizeof(buf->buf), poke_writer, buf);
 }
 
-static struct io_plan *do_write(struct io_conn *conn, struct buffer *buf)
+static struct io_plan do_write(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->writer);
 
 	return io_write(conn, &buf->buf, sizeof(buf->buf), poke_reader, buf);
 }
 
-static struct io_plan *poke_writer(struct io_conn *conn, struct buffer *buf)
+static struct io_plan poke_writer(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->reader);
 
@@ -47,7 +47,7 @@ static struct io_plan *poke_writer(struct io_conn *conn, struct buffer *buf)
 	return io_idle(conn);
 }
 
-static struct io_plan *poke_reader(struct io_conn *conn, struct buffer *buf)
+static struct io_plan poke_reader(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->writer);
 	/* You read. */
@@ -60,7 +60,7 @@ static struct io_plan *poke_reader(struct io_conn *conn, struct buffer *buf)
 	return io_idle(conn);
 }
 
-static struct io_plan *reader(struct io_conn *conn, struct buffer *buf)
+static struct io_plan reader(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->reader);
 
diff --git a/ccan/io/io.c b/ccan/io/io.c
index f7b46faa..fe9fed4f 100644
--- a/ccan/io/io.c
+++ b/ccan/io/io.c
@@ -13,8 +13,8 @@
 void *io_loop_return;
 
 struct io_listener *io_new_listener_(int fd,
-				     struct io_plan *(*start)(struct io_conn *,
-							      void *arg),
+				     struct io_plan (*start)(struct io_conn *,
+							     void *arg),
 				     void (*finish)(struct io_conn *, void *),
 				     void *arg)
 {
@@ -43,7 +43,7 @@ void io_close_listener(struct io_listener *l)
 }
 
 struct io_conn *io_new_conn_(int fd,
-			     struct io_plan *(*start)(struct io_conn *, void *),
+			     struct io_plan (*start)(struct io_conn *, void *),
 			     void (*finish)(struct io_conn *, void *),
 			     void *arg)
 {
@@ -54,11 +54,11 @@ struct io_conn *io_new_conn_(int fd,
 
 	conn->fd.listener = false;
 	conn->fd.fd = fd;
-	conn->next = start;
+	conn->plan.next = start;
 	conn->finish = finish;
-	conn->finish_arg = conn->next_arg = arg;
-	conn->pollflag = 0;
-	conn->state = IO_NEXT;
+	conn->finish_arg = conn->plan.next_arg = arg;
+	conn->plan.pollflag = 0;
+	conn->plan.state = IO_NEXT;
 	conn->duplex = NULL;
 	conn->timeout = NULL;
 	if (!add_conn(conn)) {
@@ -69,7 +69,7 @@ struct io_conn *io_new_conn_(int fd,
 }
 
 struct io_conn *io_duplex_(struct io_conn *old,
-			     struct io_plan *(*start)(struct io_conn *, void *),
+			     struct io_plan (*start)(struct io_conn *, void *),
 			     void (*finish)(struct io_conn *, void *),
 			     void *arg)
 {
@@ -83,11 +83,11 @@ struct io_conn *io_duplex_(struct io_conn *old,
 
 	conn->fd.listener = false;
 	conn->fd.fd = old->fd.fd;
-	conn->next = start;
+	conn->plan.next = start;
 	conn->finish = finish;
-	conn->finish_arg = conn->next_arg = arg;
-	conn->pollflag = 0;
-	conn->state = IO_NEXT;
+	conn->finish_arg = conn->plan.next_arg = arg;
+	conn->plan.pollflag = 0;
+	conn->plan.state = IO_NEXT;
 	conn->duplex = old;
 	conn->timeout = NULL;
 	if (!add_duplex(conn)) {
@@ -98,13 +98,8 @@ struct io_conn *io_duplex_(struct io_conn *old,
 	return conn;
 }
 
-static inline struct io_plan *to_ioplan(enum io_state state)
-{
-	return (struct io_plan *)(long)state;
-}
-
 bool io_timeout_(struct io_conn *conn, struct timespec ts,
-		 struct io_plan *(*cb)(struct io_conn *, void *), void *arg)
+		 struct io_plan (*cb)(struct io_conn *, void *), void *arg)
 {
 	if (!conn->timeout) {
 		conn->timeout = malloc(sizeof(*conn->timeout));
@@ -121,145 +116,165 @@ bool io_timeout_(struct io_conn *conn, struct timespec ts,
 
 static enum io_result do_write(struct io_conn *conn)
 {
-	ssize_t ret = write(conn->fd.fd, conn->u.write.buf, conn->u.write.len);
+	ssize_t ret = write(conn->fd.fd, conn->plan.u.write.buf, conn->plan.u.write.len);
 	if (ret < 0)
 		return RESULT_CLOSE;
 
-	conn->u.write.buf += ret;
-	conn->u.write.len -= ret;
-	if (conn->u.write.len == 0)
+	conn->plan.u.write.buf += ret;
+	conn->plan.u.write.len -= ret;
+	if (conn->plan.u.write.len == 0)
 		return RESULT_FINISHED;
 	else
 		return RESULT_AGAIN;
 }
 
 /* Queue some data to be written. */
-struct io_plan *io_write_(struct io_conn *conn, const void *data, size_t len,
-			  struct io_plan *(*cb)(struct io_conn *, void *),
-			  void *arg)
+struct io_plan io_write_(struct io_conn *conn, const void *data, size_t len,
+			 struct io_plan (*cb)(struct io_conn *, void *),
+			 void *arg)
 {
-	conn->u.write.buf = data;
-	conn->u.write.len = len;
-	conn->io = do_write;
-	conn->next = cb;
-	conn->next_arg = arg;
-	conn->pollflag = POLLOUT;
-	return to_ioplan(IO_IO);
+	struct io_plan plan;
+
+	plan.u.write.buf = data;
+	plan.u.write.len = len;
+	plan.io = do_write;
+	plan.next = cb;
+	plan.next_arg = arg;
+	plan.pollflag = POLLOUT;
+	plan.state = IO_IO;
+	return plan;
 }
 
 static enum io_result do_read(struct io_conn *conn)
 {
-	ssize_t ret = read(conn->fd.fd, conn->u.read.buf, conn->u.read.len);
+	ssize_t ret = read(conn->fd.fd, conn->plan.u.read.buf,
+			   conn->plan.u.read.len);
 	if (ret <= 0)
 		return RESULT_CLOSE;
-	conn->u.read.buf += ret;
-	conn->u.read.len -= ret;
-	if (conn->u.read.len == 0)
+	conn->plan.u.read.buf += ret;
+	conn->plan.u.read.len -= ret;
+	if (conn->plan.u.read.len == 0)
 		return RESULT_FINISHED;
 	else
 		return RESULT_AGAIN;
 }
 
 /* Queue a request to read into a buffer. */
-struct io_plan *io_read_(struct io_conn *conn, void *data, size_t len,
-			 struct io_plan *(*cb)(struct io_conn *, void *),
-			 void *arg)
+struct io_plan io_read_(struct io_conn *conn, void *data, size_t len,
+			struct io_plan (*cb)(struct io_conn *, void *),
+			void *arg)
 {
-	conn->u.read.buf = data;
-	conn->u.read.len = len;
-	conn->io = do_read;
-	conn->next = cb;
-	conn->next_arg = arg;
-	conn->pollflag = POLLIN;
-	return to_ioplan(IO_IO);
+	struct io_plan plan;
+
+	plan.u.read.buf = data;
+	plan.u.read.len = len;
+	plan.io = do_read;
+	plan.next = cb;
+	plan.next_arg = arg;
+	plan.pollflag = POLLIN;
+	plan.state = IO_IO;
+	return plan;
 }
 
 static enum io_result do_read_partial(struct io_conn *conn)
 {
-	ssize_t ret = read(conn->fd.fd, conn->u.readpart.buf,
-			   *conn->u.readpart.lenp);
+	ssize_t ret = read(conn->fd.fd, conn->plan.u.readpart.buf,
+			   *conn->plan.u.readpart.lenp);
 	if (ret <= 0)
 		return RESULT_CLOSE;
-	*conn->u.readpart.lenp = ret;
+	*conn->plan.u.readpart.lenp = ret;
 	return RESULT_FINISHED;
 }
 
 /* Queue a partial request to read into a buffer. */
-struct io_plan *io_read_partial_(struct io_conn *conn, void *data, size_t *len,
-				 struct io_plan *(*cb)(struct io_conn *, void *),
-				 void *arg)
+struct io_plan io_read_partial_(struct io_conn *conn, void *data, size_t *len,
+				struct io_plan (*cb)(struct io_conn *, void *),
+				void *arg)
 {
-	conn->u.readpart.buf = data;
-	conn->u.readpart.lenp = len;
-	conn->io = do_read_partial;
-	conn->next = cb;
-	conn->next_arg = arg;
-	conn->pollflag = POLLIN;
-	return to_ioplan(IO_IO);
+	struct io_plan plan;
+
+	plan.u.readpart.buf = data;
+	plan.u.readpart.lenp = len;
+	plan.io = do_read_partial;
+	plan.next = cb;
+	plan.next_arg = arg;
+	plan.pollflag = POLLIN;
+	plan.state = IO_IO;
+
+	return plan;
 }
 
 static enum io_result do_write_partial(struct io_conn *conn)
 {
-	ssize_t ret = write(conn->fd.fd, conn->u.writepart.buf,
-			    *conn->u.writepart.lenp);
+	ssize_t ret = write(conn->fd.fd, conn->plan.u.writepart.buf,
+			    *conn->plan.u.writepart.lenp);
 	if (ret < 0)
 		return RESULT_CLOSE;
-	*conn->u.writepart.lenp = ret;
+	*conn->plan.u.writepart.lenp = ret;
 	return RESULT_FINISHED;
 }
 
 /* Queue a partial write request. */
-struct io_plan *io_write_partial_(struct io_conn *conn,
-				  const void *data, size_t *len,
-				  struct io_plan *(*cb)(struct io_conn*, void *),
-				  void *arg)
+struct io_plan io_write_partial_(struct io_conn *conn,
+				 const void *data, size_t *len,
+				 struct io_plan (*cb)(struct io_conn*, void *),
+				 void *arg)
 {
-	conn->u.writepart.buf = data;
-	conn->u.writepart.lenp = len;
-	conn->io = do_write_partial;
-	conn->next = cb;
-	conn->next_arg = arg;
-	conn->pollflag = POLLOUT;
-	return to_ioplan(IO_IO);
+	struct io_plan plan;
+
+	plan.u.writepart.buf = data;
+	plan.u.writepart.lenp = len;
+	plan.io = do_write_partial;
+	plan.next = cb;
+	plan.next_arg = arg;
+	plan.pollflag = POLLOUT;
+	plan.state = IO_IO;
+
+	return plan;
 }
 
-struct io_plan *io_idle(struct io_conn *conn)
+struct io_plan io_idle(struct io_conn *conn)
 {
-	conn->pollflag = 0;
-	return to_ioplan(IO_IDLE);
+	struct io_plan plan;
+
+	plan.pollflag = 0;
+	plan.state = IO_IDLE;
+
+	return plan;
 }
 
 void io_wake_(struct io_conn *conn,
-	      struct io_plan *(*fn)(struct io_conn *, void *), void *arg)
+	      struct io_plan (*fn)(struct io_conn *, void *), void *arg)
 
 {
 	/* It might have finished, but we haven't called its finish() yet. */
-	if (conn->state == IO_FINISHED)
+	if (conn->plan.state == IO_FINISHED)
 		return;
-	assert(conn->state == IO_IDLE);
-	conn->next = fn;
-	conn->next_arg = arg;
-	conn->state = IO_NEXT;
+	assert(conn->plan.state == IO_IDLE);
+	conn->plan.next = fn;
+	conn->plan.next_arg = arg;
+	conn->plan.pollflag = 0;
+	conn->plan.state = IO_NEXT;
 	backend_wakeup(conn);
 }
 
-static struct io_plan *do_next(struct io_conn *conn)
+static struct io_plan do_next(struct io_conn *conn)
 {
 	if (timeout_active(conn))
 		backend_del_timeout(conn);
-	return conn->next(conn, conn->next_arg);
+	return conn->plan.next(conn, conn->plan.next_arg);
 }
 
-struct io_plan *do_ready(struct io_conn *conn)
+struct io_plan do_ready(struct io_conn *conn)
 {
-	assert(conn->state == IO_IO);
-	switch (conn->io(conn)) {
+	assert(conn->plan.state == IO_IO);
+	switch (conn->plan.io(conn)) {
 	case RESULT_CLOSE:
 		return io_close(conn, NULL);
 	case RESULT_FINISHED:
 		return do_next(conn);
 	case RESULT_AGAIN:
-		return to_ioplan(conn->state);
+		return conn->plan;
 	default:
 		abort();
 	}
@@ -267,19 +282,29 @@ struct io_plan *do_ready(struct io_conn *conn)
 
 /* Useful next functions. */
 /* Close the connection, we're done. */
-struct io_plan *io_close(struct io_conn *conn, void *arg)
+struct io_plan io_close(struct io_conn *conn, void *arg)
 {
-	return to_ioplan(IO_FINISHED);
+	struct io_plan plan;
+
+	plan.state = IO_FINISHED;
+	plan.pollflag = 0;
+
+	return plan;
 }
 
 /* Exit the loop, returning this (non-NULL) arg. */
-struct io_plan *io_break_(struct io_conn *conn, void *ret,
-			  struct io_plan *(*fn)(struct io_conn *, void *),
-			  void *arg)
+struct io_plan io_break_(struct io_conn *conn, void *ret,
+			 struct io_plan (*fn)(struct io_conn *, void *),
+			 void *arg)
 {
+	struct io_plan plan;
+
 	io_loop_return = ret;
-	conn->next = fn;
-	conn->next_arg = arg;
 
-	return to_ioplan(IO_NEXT);
+	plan.state = IO_NEXT;
+	plan.pollflag = 0;
+	plan.next = fn;
+	plan.next_arg = arg;
+
+	return plan;
 }
diff --git a/ccan/io/io.h b/ccan/io/io.h
index 9b4797a5..a027fe71 100644
--- a/ccan/io/io.h
+++ b/ccan/io/io.h
@@ -6,12 +6,60 @@
 #include <stdbool.h>
 #include <unistd.h>
 
+struct io_conn;
+
+struct io_state_read {
+	char *buf;
+	size_t len;
+};
+
+struct io_state_write {
+	const char *buf;
+	size_t len;
+};
+
+struct io_state_readpart {
+	char *buf;
+	size_t *lenp;
+};
+
+struct io_state_writepart {
+	const char *buf;
+	size_t *lenp;
+};
+
+enum io_result {
+	RESULT_AGAIN,
+	RESULT_FINISHED,
+	RESULT_CLOSE
+};
+
+enum io_state {
+	IO_IO,
+	IO_NEXT, /* eg starting, woken from idle, return from io_break. */
+	IO_IDLE,
+	IO_FINISHED
+};
+
 /**
- * struct io_plan - pointer to return from a setup function.
+ * struct io_plan - returned from a setup function.
  *
  * A plan of what IO to do, when.
  */
-struct io_plan;
+struct io_plan {
+	int pollflag;
+	enum io_state state;
+	enum io_result (*io)(struct io_conn *conn);
+	struct io_plan (*next)(struct io_conn *, void *arg);
+	void *next_arg;
+
+	union {
+		struct io_state_read read;
+		struct io_state_write write;
+		struct io_state_readpart readpart;
+		struct io_state_writepart writepart;
+	} u;
+};
 
 /**
  * io_new_conn - create a new connection.
@@ -32,13 +80,13 @@ struct io_plan;
  */
 #define io_new_conn(fd, start, finish, arg)				\
 	io_new_conn_((fd),						\
-		     typesafe_cb_preargs(struct io_plan *, void *,	\
+		     typesafe_cb_preargs(struct io_plan, void *,	\
 					 (start), (arg), struct io_conn *), \
 		     typesafe_cb_preargs(void, void *, (finish), (arg),	\
 					 struct io_conn *),		\
 		     (arg))
 struct io_conn *io_new_conn_(int fd,
-			     struct io_plan *(*start)(struct io_conn *, void *),
+			     struct io_plan (*start)(struct io_conn *, void *),
 			     void (*finish)(struct io_conn *, void *),
 			     void *arg);
 
@@ -56,14 +104,14 @@ struct io_conn *io_new_conn_(int fd,
  */
 #define io_new_listener(fd, start, finish, arg)				\
 	io_new_listener_((fd),						\
-			 typesafe_cb_preargs(struct io_plan *, void *,	\
+			 typesafe_cb_preargs(struct io_plan, void *,	\
 					     (start), (arg),		\
 					     struct io_conn *),		\
 			 typesafe_cb_preargs(void, void *, (finish),	\
 					     (arg), struct io_conn *),	\
 			 (arg))
 struct io_listener *io_new_listener_(int fd,
-				     struct io_plan *(*start)(struct io_conn *,
+				     struct io_plan (*start)(struct io_conn *,
 							      void *arg),
 				     void (*finish)(struct io_conn *,
 						    void *arg),
@@ -93,12 +141,12 @@ void io_close_listener(struct io_listener *listener);
  */
 #define io_write(conn, data, len, cb, arg)				\
 	io_write_((conn), (data), (len),				\
-		  typesafe_cb_preargs(struct io_plan *, void *,		\
+		  typesafe_cb_preargs(struct io_plan, void *,		\
 				      (cb), (arg), struct io_conn *),	\
 		  (arg))
-struct io_plan *io_write_(struct io_conn *conn, const void *data, size_t len,
-			  struct io_plan *(*cb)(struct io_conn *, void *),
-			  void *arg);
+struct io_plan io_write_(struct io_conn *conn, const void *data, size_t len,
+			 struct io_plan (*cb)(struct io_conn *, void *),
+			 void *arg);
 
 /**
  * io_read - queue buffer to be read.
@@ -116,12 +164,12 @@ struct io_plan *io_write_(struct io_conn *conn, const void *data, size_t len,
  */
 #define io_read(conn, data, len, cb, arg)				\
 	io_read_((conn), (data), (len),					\
-		 typesafe_cb_preargs(struct io_plan *, void *,		\
+		 typesafe_cb_preargs(struct io_plan, void *,		\
 				     (cb), (arg), struct io_conn *),	\
 		 (arg))
-struct io_plan *io_read_(struct io_conn *conn, void *data, size_t len,
-			 struct io_plan *(*cb)(struct io_conn *, void *),
-			 void *arg);
+struct io_plan io_read_(struct io_conn *conn, void *data, size_t len,
+			struct io_plan (*cb)(struct io_conn *, void *),
+			void *arg);
 
 
 /**
@@ -140,12 +188,12 @@ struct io_plan *io_read_(struct io_conn *conn, void *data, size_t len,
  */
 #define io_read_partial(conn, data, len, cb, arg)			\
 	io_read_partial_((conn), (data), (len),				\
-			 typesafe_cb_preargs(struct io_plan *, void *,	\
+			 typesafe_cb_preargs(struct io_plan, void *,	\
 					     (cb), (arg), struct io_conn *), \
 			 (arg))
-struct io_plan *io_read_partial_(struct io_conn *conn, void *data, size_t *len,
-				 struct io_plan *(*cb)(struct io_conn *, void *),
-				 void *arg);
+struct io_plan io_read_partial_(struct io_conn *conn, void *data, size_t *len,
+				struct io_plan (*cb)(struct io_conn *, void *),
+				void *arg);
 
 /**
  * io_write_partial - queue data to be written (partial OK).
@@ -163,13 +211,13 @@ struct io_plan *io_read_partial_(struct io_conn *conn, void *data, size_t *len,
  */
 #define io_write_partial(conn, data, len, cb, arg)			\
 	io_write_partial_((conn), (data), (len),			\
-			  typesafe_cb_preargs(struct io_plan *, void *,	\
+			  typesafe_cb_preargs(struct io_plan, void *,	\
 					      (cb), (arg), struct io_conn *), \
 			  (arg))
-struct io_plan *io_write_partial_(struct io_conn *conn,
-				  const void *data, size_t *len,
-				  struct io_plan *(*cb)(struct io_conn *, void*),
-				  void *arg);
+struct io_plan io_write_partial_(struct io_conn *conn,
+				 const void *data, size_t *len,
+				 struct io_plan (*cb)(struct io_conn *, void*),
+				 void *arg);
 
 
 /**
@@ -180,7 +228,7 @@ struct io_plan *io_write_partial_(struct io_conn *conn,
  * later call io_read/io_write etc. (or io_close) on it, in which case
  * it will do that.
  */
-struct io_plan *io_idle(struct io_conn *conn);
+struct io_plan io_idle(struct io_conn *conn);
 
 /**
  * io_timeout - set timeout function if the callback doesn't fire.
@@ -198,12 +246,12 @@ struct io_plan *io_idle(struct io_conn *conn);
  */
 #define io_timeout(conn, ts, fn, arg)					\
 	io_timeout_((conn), (ts),					\
-		    typesafe_cb_preargs(struct io_plan *, void *,	\
+		    typesafe_cb_preargs(struct io_plan, void *,		\
 					(fn), (arg),			\
 					struct io_conn *),		\
 		    (arg))
 bool io_timeout_(struct io_conn *conn, struct timespec ts,
-		 struct io_plan *(*fn)(struct io_conn *, void *), void *arg);
+		 struct io_plan (*fn)(struct io_conn *, void *), void *arg);
 
 /**
  * io_duplex - split an fd into two connections.
@@ -221,14 +269,14 @@ bool io_timeout_(struct io_conn *conn, struct timespec ts,
  */
 #define io_duplex(conn, start, finish, arg)				\
 	io_duplex_((conn),						\
-		   typesafe_cb_preargs(struct io_plan *, void *,	\
+		   typesafe_cb_preargs(struct io_plan, void *,		\
 				       (start), (arg), struct io_conn *), \
 		   typesafe_cb_preargs(void, void *, (finish), (arg),	\
 				       struct io_conn *),		\
 		   (arg))
 
 struct io_conn *io_duplex_(struct io_conn *conn,
-			   struct io_plan *(*start)(struct io_conn *, void *),
+			   struct io_plan (*start)(struct io_conn *, void *),
 			   void (*finish)(struct io_conn *, void *),
 			   void *arg);
 
@@ -243,11 +291,11 @@ struct io_conn *io_duplex_(struct io_conn *conn,
  */
 #define io_wake(conn, fn, arg)						\
 	io_wake_((conn),						\
-		 typesafe_cb_preargs(struct io_plan *, void *,		\
+		 typesafe_cb_preargs(struct io_plan, void *,		\
 				     (fn), (arg), struct io_conn *),	\
 		 (arg))
 void io_wake_(struct io_conn *conn,
-	      struct io_plan *(*fn)(struct io_conn *, void *), void *arg);
+	      struct io_plan (*fn)(struct io_conn *, void *), void *arg);
 
 /**
  * io_break - return from io_loop()
@@ -264,12 +312,12 @@ void io_wake_(struct io_conn *conn,
  */
 #define io_break(conn, ret, fn, arg)					\
 	io_break_((conn), (ret),					\
-		  typesafe_cb_preargs(struct io_plan *, void *,		\
+		  typesafe_cb_preargs(struct io_plan, void *,		\
 				      (fn), (arg), struct io_conn *),	\
 		  (arg))
-struct io_plan *io_break_(struct io_conn *conn, void *ret,
-			  struct io_plan *(*fn)(struct io_conn *, void *),
-			  void *arg);
+struct io_plan io_break_(struct io_conn *conn, void *ret,
+			 struct io_plan (*fn)(struct io_conn *, void *),
+			 void *arg);
 
 /* FIXME: io_recvfrom/io_sendto */
 
@@ -284,7 +332,7 @@ struct io_plan *io_break_(struct io_conn *conn, void *ret,
  * It's common to 'return io_close(...)' from a @next function, but
  * io_close can also be used as an argument to io_next().
  */
-struct io_plan *io_close(struct io_conn *, void *unused);
+struct io_plan io_close(struct io_conn *, void *unused);
 
 /**
  * io_loop - process fds until all closed on io_break.
diff --git a/ccan/io/poll.c b/ccan/io/poll.c
index 0cc84ad9..adf7bb0c 100644
--- a/ccan/io/poll.c
+++ b/ccan/io/poll.c
@@ -101,9 +101,9 @@ static void del_conn(struct io_conn *conn)
 		conn->duplex->duplex = NULL;
 	} else
 		del_fd(&conn->fd);
-	if (conn->state == IO_FINISHED)
+	if (conn->plan.state == IO_FINISHED)
 		num_finished--;
-	else if (conn->state == IO_NEXT)
+	else if (conn->plan.state == IO_NEXT)
 		num_next--;
 }
 
@@ -112,17 +112,16 @@ void del_listener(struct io_listener *l)
 	del_fd(&l->fd);
 }
 
-static void backend_set_state(struct io_conn *conn, struct io_plan *plan)
+static void backend_set_state(struct io_conn *conn, struct io_plan plan)
 {
-	enum io_state state = from_ioplan(plan);
 	struct pollfd *pfd = &pollfds[conn->fd.backend_info];
 
 	if (pfd->events)
 		num_waiting--;
 
-	pfd->events = conn->pollflag;
+	pfd->events = plan.pollflag;
 	if (conn->duplex) {
-		int mask = conn->duplex->pollflag;
+		int mask = conn->duplex->plan.pollflag;
 		/* You can't *both* read/write. */
 		assert(!mask || pfd->events != mask);
 		pfd->events |= mask;
@@ -130,12 +129,12 @@ static void backend_set_state(struct io_conn *conn, struct io_plan *plan)
 	if (pfd->events)
 		num_waiting++;
 
-	if (state == IO_NEXT)
+	if (plan.state == IO_NEXT)
 		num_next++;
-	else if (state == IO_FINISHED)
+	else if (plan.state == IO_FINISHED)
 		num_finished++;
 
-	conn->state = state;
+	conn->plan = plan;
 }
 
 void backend_wakeup(struct io_conn *conn)
@@ -174,12 +173,12 @@ static void finish_and_next(bool finished_only)
 			continue;
 		c = (void *)fds[i];
 		for (duplex = c->duplex; c; c = duplex, duplex = NULL) {
-			if (c->state == IO_FINISHED) {
+			if (c->plan.state == IO_FINISHED) {
 				del_conn(c);
 				free(c);
 				i--;
-			} else if (!finished_only && c->state == IO_NEXT) {
-				backend_set_state(c, c->next(c, c->next_arg));
+			} else if (!finished_only && c->plan.state == IO_NEXT) {
+				backend_set_state(c, c->plan.next(c, c->plan.next_arg));
 				num_next--;
 			}
 		}
@@ -271,7 +270,7 @@ void *io_loop(void)
 			} else if (events & (POLLIN|POLLOUT)) {
 				r--;
 				if (c->duplex) {
-					int mask = c->duplex->pollflag;
+					int mask = c->duplex->plan.pollflag;
 					if (events & mask) {
 						ready(c->duplex);
 						events &= ~mask;
diff --git a/ccan/io/test/run-01-start-finish.c b/ccan/io/test/run-01-start-finish.c
index a2393d9f..7c6ae415 100644
--- a/ccan/io/test/run-01-start-finish.c
+++ b/ccan/io/test/run-01-start-finish.c
@@ -6,7 +6,7 @@
 #include <sys/wait.h>
 #include <stdio.h>
 
-static struct io_plan *start_ok(struct io_conn *conn, int *state)
+static struct io_plan start_ok(struct io_conn *conn, int *state)
 {
 	ok1(*state == 0);
 	(*state)++;
diff --git a/ccan/io/test/run-02-read.c b/ccan/io/test/run-02-read.c
index 4e184909..8b96f029 100644
--- a/ccan/io/test/run-02-read.c
+++ b/ccan/io/test/run-02-read.c
@@ -11,7 +11,7 @@ struct data {
 	char buf[4];
 };
 
-static struct io_plan *start_ok(struct io_conn *conn, struct data *d)
+static struct io_plan start_ok(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 0);
 	d->state++;
diff --git a/ccan/io/test/run-03-readpartial.c b/ccan/io/test/run-03-readpartial.c
index 9e97f49a..e6e33e3d 100644
--- a/ccan/io/test/run-03-readpartial.c
+++ b/ccan/io/test/run-03-readpartial.c
@@ -12,7 +12,7 @@ struct data {
 	char buf[4];
 };
 
-static struct io_plan *start_ok(struct io_conn *conn, struct data *d)
+static struct io_plan start_ok(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 0);
 	d->state++;
diff --git a/ccan/io/test/run-04-writepartial.c b/ccan/io/test/run-04-writepartial.c
index 87fa8d9d..d4e33c96 100644
--- a/ccan/io/test/run-04-writepartial.c
+++ b/ccan/io/test/run-04-writepartial.c
@@ -12,7 +12,7 @@ struct data {
 	char *buf;
 };
 
-static struct io_plan *start_ok(struct io_conn *conn, struct data *d)
+static struct io_plan start_ok(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 0);
 	d->state++;
diff --git a/ccan/io/test/run-05-write.c b/ccan/io/test/run-05-write.c
index 1181bec0..ad6760e4 100644
--- a/ccan/io/test/run-05-write.c
+++ b/ccan/io/test/run-05-write.c
@@ -12,7 +12,7 @@ struct data {
 	char *buf;
 };
 
-static struct io_plan *start_ok(struct io_conn *conn, struct data *d)
+static struct io_plan start_ok(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 0);
 	d->state++;
diff --git a/ccan/io/test/run-06-idle.c b/ccan/io/test/run-06-idle.c
index 597060c2..19d0f8b1 100644
--- a/ccan/io/test/run-06-idle.c
+++ b/ccan/io/test/run-06-idle.c
@@ -16,14 +16,14 @@ struct data {
 	char buf[4];
 };
 
-static struct io_plan *plan_read(struct io_conn *conn, struct data *d)
+static struct io_plan plan_read(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 2 || d->state == 3);
 	d->state++;
 	return io_read(conn, d->buf, sizeof(d->buf), io_close, d);
 }
 
-static struct io_plan *start_waker(struct io_conn *conn, struct data *d)
+static struct io_plan start_waker(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 1);
 	d->state++;
@@ -38,7 +38,7 @@ static void finish_waker(struct io_conn *conn, struct data *d)
 	d->state++;
 }
 
-static struct io_plan *start_idle(struct io_conn *conn, struct data *d)
+static struct io_plan start_idle(struct io_conn *conn, struct data *d)
 {
 	int fd;
 
diff --git a/ccan/io/test/run-07-break.c b/ccan/io/test/run-07-break.c
index 3dac4ece..5bc0e8c6 100644
--- a/ccan/io/test/run-07-break.c
+++ b/ccan/io/test/run-07-break.c
@@ -11,14 +11,14 @@ struct data {
 	char buf[4];
 };
 
-static struct io_plan *plan_read(struct io_conn *conn, struct data *d)
+static struct io_plan plan_read(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 1);
 	d->state++;
 	return io_read(conn, d->buf, sizeof(d->buf), io_close, d);
 }
 
-static struct io_plan *start_break(struct io_conn *conn, struct data *d)
+static struct io_plan start_break(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 0);
 	d->state++;
diff --git a/ccan/io/test/run-10-many.c b/ccan/io/test/run-10-many.c
index 31369118..91b335e1 100644
--- a/ccan/io/test/run-10-many.c
+++ b/ccan/io/test/run-10-many.c
@@ -15,10 +15,10 @@ struct buffer {
 	char buf[32];
 };
 
-static struct io_plan *poke_writer(struct io_conn *conn, struct buffer *buf);
-static struct io_plan *poke_reader(struct io_conn *conn, struct buffer *buf);
+static struct io_plan poke_writer(struct io_conn *conn, struct buffer *buf);
+static struct io_plan poke_reader(struct io_conn *conn, struct buffer *buf);
 
-static struct io_plan *plan_read(struct io_conn *conn, struct buffer *buf)
+static struct io_plan plan_read(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->reader);
 
@@ -26,7 +26,7 @@ static struct io_plan *plan_read(struct io_conn *conn, struct buffer *buf)
 		       poke_writer, buf);
 }
 
-static struct io_plan *plan_write(struct io_conn *conn, struct buffer *buf)
+static struct io_plan plan_write(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->writer);
 
@@ -34,7 +34,7 @@ static struct io_plan *plan_write(struct io_conn *conn, struct buffer *buf)
 			poke_reader, buf);
 }
 
-static struct io_plan *poke_writer(struct io_conn *conn, struct buffer *buf)
+static struct io_plan poke_writer(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->reader);
 
@@ -48,7 +48,7 @@ static struct io_plan *poke_writer(struct io_conn *conn, struct buffer *buf)
 	return io_idle(conn);
 }
 
-static struct io_plan *poke_reader(struct io_conn *conn, struct buffer *buf)
+static struct io_plan poke_reader(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->writer);
 	/* You read. */
@@ -61,7 +61,7 @@ static struct io_plan *poke_reader(struct io_conn *conn, struct buffer *buf)
 	return io_idle(conn);
 }
 
-static struct io_plan *reader(struct io_conn *conn, struct buffer *buf)
+static struct io_plan reader(struct io_conn *conn, struct buffer *buf)
 {
 	assert(conn == buf->reader);
 
diff --git a/ccan/io/test/run-12-bidir.c b/ccan/io/test/run-12-bidir.c
index eb4f4f05..0cafb4f2 100644
--- a/ccan/io/test/run-12-bidir.c
+++ b/ccan/io/test/run-12-bidir.c
@@ -18,13 +18,13 @@ static void finish_ok(struct io_conn *conn, struct data *d)
 	d->state++;
 }
 
-static struct io_plan *write_out(struct io_conn *conn, struct data *d)
+static struct io_plan write_out(struct io_conn *conn, struct data *d)
 {
 	d->state++;
 	return io_write(conn, d->wbuf, sizeof(d->wbuf), io_close, d);
 }
 
-static struct io_plan *start_ok(struct io_conn *conn, struct data *d)
+static struct io_plan start_ok(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 0);
 	d->state++;
diff --git a/ccan/io/test/run-13-all-idle.c b/ccan/io/test/run-13-all-idle.c
index 48be71dd..178b68a8 100644
--- a/ccan/io/test/run-13-all-idle.c
+++ b/ccan/io/test/run-13-all-idle.c
@@ -7,7 +7,7 @@
 #include <stdio.h>
 #include <signal.h>
 
-static struct io_plan *start(struct io_conn *conn, void *unused)
+static struct io_plan start(struct io_conn *conn, void *unused)
 {
 	return io_idle(conn);
 }
diff --git a/ccan/io/test/run-15-timeout.c b/ccan/io/test/run-15-timeout.c
index 510a9720..5e94b8c0 100644
--- a/ccan/io/test/run-15-timeout.c
+++ b/ccan/io/test/run-15-timeout.c
@@ -15,14 +15,14 @@ struct data {
 };
 
 
-static struct io_plan *no_timeout(struct io_conn *conn, struct data *d)
+static struct io_plan no_timeout(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 1);
 	d->state++;
 	return io_close(conn, d);
 }
 
-static struct io_plan *timeout(struct io_conn *conn, struct data *d)
+static struct io_plan timeout(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 1);
 	d->state++;
@@ -30,7 +30,7 @@ static struct io_plan *timeout(struct io_conn *conn, struct data *d)
 	return io_close(conn, d);
 }
 
-static struct io_plan *start_ok(struct io_conn *conn, struct data *d)
+static struct io_plan start_ok(struct io_conn *conn, struct data *d)
 {
 	ok1(d->state == 0);
 	d->state++;