ccan/io: io_halfclose.

Helper for a common case.  Replace all but 1 in tests.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/io/io.c

@@ -437,6 +437,24 @@ struct io_plan *io_duplex_(struct io_plan *in_plan, struct io_plan *out_plan)
 	return out_plan + 1;
 }
 
+struct io_plan *io_halfclose(struct io_conn *conn)
+{
+	/* Already closing?  Don't close twice. */
+	if (conn->plan[IO_IN].status == IO_CLOSING)
+		return &conn->plan[IO_IN];
+
+	/* Both unset?  OK. */
+	if (conn->plan[IO_IN].status == IO_UNSET
+	    && conn->plan[IO_OUT].status == IO_UNSET)
+		return io_close(conn);
+
+	/* We leave this unset then. */
+	if (conn->plan[IO_IN].status == IO_UNSET)
+		return &conn->plan[IO_IN];
+	else
+		return &conn->plan[IO_OUT];
+}
+
 struct io_plan *io_set_plan(struct io_conn *conn, enum io_direction dir,
 			    int (*io)(int fd, struct io_plan_arg *arg),
 			    struct io_plan *(*next)(struct io_conn *, void *),

ccan/io/io.h

@@ -443,6 +443,34 @@ struct io_plan *io_connect_(struct io_conn *conn, const struct addrinfo *addr,
 struct io_plan *io_duplex_(struct io_plan *in_plan, struct io_plan *out_plan);
 void io_duplex_prepare(struct io_conn *conn);
 
+/**
+ * io_halfclose - close half of an io_duplex connection.
+ * @conn: the connection that plan is for.
+ *
+ * It's common to want to close a duplex connection after both input and
+ * output plans have completed.  If either calls io_close() the connection
+ * closes immediately.  Instead, io_halfclose() needs to be called twice.
+ *
+ * Example:
+ * struct buf {
+ *	char in[100];
+ *	char out[100];
+ * };
+ *
+ * static struct io_plan *finish(struct io_conn *conn, struct buf *b)
+ * {
+ *	return io_halfclose(conn);
+ * }
+ *
+ * static struct io_plan *read_and_write(struct io_conn *conn, struct buf *b)
+ * {
+ *	return io_duplex(conn,
+ *			 io_read(conn, b->in, sizeof(b->in), finish, b),
+ *			 io_write(conn, b->out, sizeof(b->out), finish, b));
+ * }
+ */
+struct io_plan *io_halfclose(struct io_conn *conn);
+
 /**
  * io_wait - leave a plan idle until something wakes us.
  * @conn: the connection that plan is for.

ccan/io/test/run-12-bidir.c

@@ -15,7 +15,6 @@
 struct data {
 	struct io_listener *l;
 	int state;
-	int done;
 	char buf[4];
 	char wbuf[32];
 };
@@ -28,10 +27,7 @@ static void finish_ok(struct io_conn *conn, struct data *d)
 static struct io_plan *rw_done(struct io_conn *conn, struct data *d)
 {
 	d->state++;
-	d->done++;
-	if (d->done == 2)
-		return io_close(conn);
-	return io_wait(conn, NULL, io_never, NULL);
+	return io_halfclose(conn);
 }
 
 static struct io_plan *init_conn(struct io_conn *conn, struct data *d)
@@ -91,9 +87,8 @@ int main(void)
 	int fd, status;
 
 	/* This is how many tests you plan to run */
-	plan_tests(10);
+	plan_tests(9);
 	d->state = 0;
-	d->done = 0;
 	fd = make_listen_fd(PORT, &addrinfo);
 	ok1(fd >= 0);
 	d->l = io_new_listener(NULL, fd, init_conn, d);
@@ -127,7 +122,6 @@ int main(void)
 	freeaddrinfo(addrinfo);
 	ok1(io_loop(NULL, NULL) == NULL);
 	ok1(d->state == 4);
-	ok1(d->done == 2);
 	ok1(memcmp(d->buf, "hellothere", sizeof(d->buf)) == 0);
 	free(d);
 

ccan/io/test/run-14-duplex-both-read.c

@@ -29,10 +29,11 @@ static void finish_ok(struct io_conn *conn, struct data *d)
 static struct io_plan *end(struct io_conn *conn, struct data *d)
 {
 	d->state++;
+	/* Close on top of halfclose should work. */
 	if (d->state == 4)
 		return io_close(conn);
 	else
-		return io_wait(conn, NULL, io_never, NULL);
+		return io_halfclose(conn);
 }
 
 static struct io_plan *make_duplex(struct io_conn *conn, struct data *d)

ccan/io/test/run-16-duplex-test.c

@@ -29,9 +29,7 @@ static void finish_ok(struct io_conn *conn, struct data *d)
 static struct io_plan *io_done(struct io_conn *conn, struct data *d)
 {
 	d->state++;
-	if (d->state == 3)
-		return io_close(conn);
-	return io_wait(conn, d, io_close_cb, NULL);
+	return io_halfclose(conn);
 }
 
 static struct io_plan *init_conn(struct io_conn *conn, struct data *d)