ccan/io: add examples.

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

ccan/io/io.h

@@ -16,6 +16,16 @@
  * next io_loop().
  *
  * Returns NULL on error (and sets errno).
+ *
+ * Example:
+ *	int fd[2];
+ *	struct io_conn *conn;
+ *
+ *	pipe(fd);
+ *	// Plan is to close the fd immediately.
+ *	conn = io_new_conn(fd[0], io_close());
+ *	if (!conn)
+ *		exit(1);
  */
 #define io_new_conn(fd, plan)				\
 	(io_plan_no_debug(), io_new_conn_((fd), (plan)))
@@ -30,6 +40,15 @@ 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
  * after the failed I/O, or at the call to io_close().
+ *
+ * Example:
+ * static void finish(struct io_conn *conn, void *unused)
+ * {
+ *	// errno is not 0 after success, so this is a bit useless.
+ *	printf("Conn %p closed with errno %i\n", conn, errno);
+ * }
+ * ...
+ *	io_set_finish(conn, finish, NULL);
  */
 #define io_set_finish(conn, finish, arg)				\
 	io_set_finish_((conn),						\
@@ -50,6 +69,50 @@ void io_set_finish_(struct io_conn *conn,
  * When @fd becomes readable, we accept() and pass that fd to init().
  *
  * Returns NULL on error (and sets errno).
+ *
+ * Example:
+ * #include <sys/types.h>
+ * #include <sys/socket.h>
+ * #include <netdb.h>
+ *
+ * static void start_conn(int fd, char *msg)
+ * {
+ *	printf("%s fd %i\n", msg, fd);
+ *	close(fd);
+ * }
+ *
+ * // Set up a listening socket, return it.
+ * static struct io_listener *do_listen(const char *port)
+ * {
+ *	struct addrinfo *addrinfo, hints;
+ *	int fd, on = 1;
+ *
+ *	memset(&hints, 0, sizeof(hints));
+ *	hints.ai_family = AF_UNSPEC;
+ *	hints.ai_socktype = SOCK_STREAM;
+ *	hints.ai_flags = AI_PASSIVE;
+ *	hints.ai_protocol = 0;
+ *
+ *	if (getaddrinfo(NULL, port, &hints, &addrinfo) != 0)
+ *		return NULL;
+ *
+ *	fd = socket(addrinfo->ai_family, addrinfo->ai_socktype,
+ *		    addrinfo->ai_protocol);
+ *	if (fd < 0)
+ *		return NULL;
+ *
+ *	freeaddrinfo(addrinfo);
+ *	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
+ *	if (bind(fd, addrinfo->ai_addr, addrinfo->ai_addrlen) != 0) {
+ *		close(fd);
+ *		return NULL;
+ *	}
+ *	if (listen(fd, 1) != 0) {
+ *		close(fd);
+ *		return NULL;
+ *	}
+ *	return io_new_listener(fd, start_conn, (char *)"Got one!");
+ * }
  */
 #define io_new_listener(fd, init, arg)					\
 	io_new_listener_((fd),						\
@@ -66,6 +129,14 @@ struct io_listener *io_new_listener_(int fd,
  * @listener: the listener returned from io_new_listener.
  *
  * This closes the fd and frees @listener.
+ *
+ * Example:
+ * ...
+ *	struct io_listener *l = do_listen("8111");
+ *	if (l) {
+ *		io_loop();
+ *		io_close_listener(l);
+ *	}
  */
 void io_close_listener(struct io_listener *listener);
 
@@ -81,6 +152,13 @@ void io_close_listener(struct io_listener *listener);
  * function is called instead.
  *
  * Note that the I/O may actually be done immediately.
+ *
+ * Example:
+ * static void start_conn_with_write(int fd, const char *msg)
+ * {
+ *	// Write message, then close.
+ *	io_new_conn(fd, io_write(msg, strlen(msg), io_close_cb, NULL));
+ * }
  */
 #define io_write(data, len, cb, arg)					\
 	io_debug(io_write_((data), (len),				\
@@ -103,6 +181,13 @@ struct io_plan io_write_(const void *data, size_t len,
  * function is called instead.
  *
  * Note that the I/O may actually be done immediately.
+ *
+ * Example:
+ * static void start_conn_with_read(int fd, char msg[12])
+ * {
+ *	// Read message, then close.
+ *	io_new_conn(fd, io_read(msg, 12, io_close_cb, NULL));
+ * }
  */
 #define io_read(data, len, cb, arg)					\
 	io_debug(io_read_((data), (len),				\
@@ -126,6 +211,28 @@ struct io_plan io_read_(void *data, size_t len,
  * error, the finish function is called instead.
  *
  * Note that the I/O may actually be done immediately.
+ *
+ * Example:
+ * struct buf {
+ *	size_t len;
+ *	char buf[12];
+ * };
+ *
+ * static struct io_plan dump_and_close(struct io_conn *conn, struct buf *b)
+ * {
+ *	printf("Partial read: '%*s'\n", (int)b->len, b->buf);
+ *	free(b);
+ *	return io_close();
+ * }
+ *
+ * static void start_conn_with_part_read(int fd, void *unused)
+ * {
+ *	struct buf *b = malloc(sizeof(*b));
+ *
+ *	// Read message, then dump and close.
+ *	b->len = sizeof(b->buf);
+ *	io_new_conn(fd, io_read_partial(b->buf, &b->len, dump_and_close, b));
+ * }
  */
 #define io_read_partial(data, len, cb, arg)				\
 	io_debug(io_read_partial_((data), (len),			\
@@ -149,6 +256,29 @@ struct io_plan io_read_partial_(void *data, size_t *len,
  * error, the finish function is called instead.
  *
  * Note that the I/O may actually be done immediately.
+ *
+ * Example:
+ * struct buf {
+ *	size_t len;
+ *	char buf[12];
+ * };
+ *
+ * static struct io_plan show_remainder(struct io_conn *conn, struct buf *b)
+ * {
+ *	printf("Only wrote: '%*s'\n", (int)b->len, b->buf);
+ *	free(b);
+ *	return io_close();
+ * }
+ *
+ * static void start_conn_with_part_read(int fd, void *unused)
+ * {
+ *	struct buf *b = malloc(sizeof(*b));
+ *
+ *	// Write message, then dump and close.
+ *	b->len = sizeof(b->buf);
+ *	strcpy(b->buf, "Hello world");
+ *	io_new_conn(fd, io_write_partial(b->buf, &b->len, show_remainder, b));
+ * }
  */
 #define io_write_partial(data, len, cb, arg)				\
 	io_debug(io_write_partial_((data), (len),			\
@@ -173,6 +303,26 @@ struct io_plan io_write_partial_(const void *data, size_t *len,
  * function is called instead.
  *
  * Note that the connect may actually be done immediately.
+ *
+ * Example:
+ * #include <sys/types.h>
+ * #include <sys/socket.h>
+ * #include <netdb.h>
+ *
+ * // Write, then close socket.
+ * static struct io_plan start_write(struct io_conn *conn, void *unused)
+ * {
+ *	return io_write("hello", 5, io_close_cb, NULL);
+ * }
+ *
+ * ...
+ *
+ *	int fd;
+ *	struct addrinfo *addrinfo;
+ *
+ *	fd = socket(AF_INET, SOCK_STREAM, 0);
+ *	getaddrinfo("localhost", "8111", NULL, &addrinfo);
+ *	io_new_conn(fd, io_connect(fd, addrinfo, start_write, NULL));
  */
 struct addrinfo;
 #define io_connect(fd, addr, cb, arg)					\
@@ -190,6 +340,12 @@ struct io_plan io_connect_(int fd, const struct addrinfo *addr,
  *
  * This indicates the connection is idle: io_wake() will be called later do
  * give the connection a new plan.
+ *
+ * Example:
+ *	struct io_conn *sleeper;
+ *	sleeper = io_new_conn(open("/dev/null", O_RDONLY), io_idle());
+ *	if (!sleeper)
+ *		exit(1);
  */
 #define io_idle() io_debug(io_idle_())
 struct io_plan io_idle_(void);
@@ -207,6 +363,17 @@ struct io_plan io_idle_(void);
  *
  * Returns false on allocation failure.  A connection can only have one
  * timeout.
+ *
+ * Example:
+ *	static struct io_plan close_on_timeout(struct io_conn *conn, char *msg)
+ *	{
+ *		printf("%s\n", msg);
+ *		return io_close();
+ *	}
+ *
+ *	...
+ *	io_timeout(sleeper, time_from_msec(100),
+ *		   close_on_timeout, (char *)"Bye!");
  */
 #define io_timeout(conn, ts, fn, arg)					\
 	io_timeout_((conn), (ts),					\
@@ -228,6 +395,21 @@ bool io_timeout_(struct io_conn *conn, struct timespec ts,
  * operations and one for write.
  *
  * You must io_close() both of them to close the fd.
+ *
+ * Example:
+ *	static void setup_read_write(int fd,
+ *				     char greet_in[5], const char greet_out[5])
+ *	{
+ *		struct io_conn *writer, *reader;
+ *
+ *		// Read their greeting and send ours at the same time.
+ *		writer = io_new_conn(fd,
+ *				     io_write(greet_out, 5, io_close_cb, NULL));
+ *		reader = io_duplex(writer,
+ *				     io_read(greet_in, 5, io_close_cb, NULL));
+ *		if (!reader || !writer)
+ *			exit(1);
+ *	}
  */
 #define io_duplex(conn, plan)				\
 	(io_plan_no_debug(), io_duplex_((conn), (plan)))
@@ -239,6 +421,12 @@ struct io_conn *io_duplex_(struct io_conn *conn, struct io_plan plan);
  * @plan: the next I/O plan for @conn.
  *
  * This makes @conn ready to do I/O the next time around the io_loop().
+ *
+ * Example:
+ *	struct io_conn *sleeper;
+ *	sleeper = io_new_conn(open("/dev/null", O_RDONLY), io_idle());
+ *
+ *	io_wake(sleeper, io_write("junk", 4, io_close_cb, NULL));
  */
 #define io_wake(conn, plan) (io_plan_no_debug(), io_wake_((conn), (plan)))
 void io_wake_(struct io_conn *conn, struct io_plan plan);
@@ -253,6 +441,12 @@ void io_wake_(struct io_conn *conn, struct io_plan plan);
  * finish callbacks called, then io_loop() with return with @ret.
  *
  * If io_loop() is called again, then @plan will be carried out.
+ *
+ * Example:
+ *	static struct io_plan fail_on_timeout(struct io_conn *conn, char *msg)
+ *	{
+ *		return io_break(msg, io_close());
+ *	}
  */
 #define io_break(ret, plan) (io_plan_no_debug(), io_break_((ret), (plan)))
 struct io_plan io_break_(void *ret, struct io_plan plan);
@@ -263,6 +457,13 @@ struct io_plan io_break_(void *ret, struct io_plan plan);
  * io_close - plan to close a connection.
  *
  * On return to io_loop, the connection will be closed.
+ *
+ * Example:
+ * static struct io_plan close_on_timeout(struct io_conn *conn, const char *msg)
+ * {
+ *	printf("closing: %s\n", msg);
+ *	return io_close();
+ * }
  */
 #define io_close() io_debug(io_close_())
 struct io_plan io_close_(void);
@@ -273,6 +474,9 @@ struct io_plan io_close_(void);
  *
  * This schedules a connection to be closed; designed to be used as
  * a callback function.
+ *
+ * Example:
+ *	#define close_on_timeout io_close_cb
  */
 struct io_plan io_close_cb(struct io_conn *, void *unused);
 
@@ -281,6 +485,9 @@ struct io_plan io_close_cb(struct io_conn *, void *unused);
  *
  * This is the core loop; it exits with the io_break() arg, or NULL if
  * all connections and listeners are closed.
+ *
+ * Example:
+ *	io_loop();
  */
 void *io_loop(void);
 #endif /* CCAN_IO_H */

ccan/io/io_plan.h

@@ -68,6 +68,17 @@ struct io_plan {
  * If this is set, the routine should return true if the connection is a
  * debugging candidate.  If so, the callchain for I/O operations on this
  * connection will be linear, for easier use of a debugger.
+ *
+ * You will also see calls to any callbacks which wake the connection
+ * which is being debugged.
+ *
+ * Example:
+ *	static bool debug_all(struct io_conn *conn)
+ *	{
+ *		return true();
+ *	}
+ *	...
+ *	io_debug_conn = debug_all;
  */
 extern bool (*io_debug_conn)(struct io_conn *conn);
 
@@ -77,6 +88,10 @@ extern bool (*io_debug_conn)(struct io_conn *conn);
  * This determines if we are debugging the current connection: if so,
  * it immediately applies the plan and calls back into io_loop() to
  * create a linear call chain.
+ *
+ * Example:
+ *	#define io_idle() io_debug(io_idle_())
+ *	struct io_plan io_idle_(void);
  */
 struct io_plan io_debug(struct io_plan plan);
 
@@ -86,6 +101,19 @@ struct io_plan io_debug(struct io_plan plan);
  * This determines if we are debugging the current connection: if so,
  * it immediately sets the next function and calls into io_loop() to
  * create a linear call chain.
+ *
+ * Example:
+ *
+ * static int do_write(int fd, struct io_plan *plan)
+ * {
+ *	ssize_t ret = write(fd, plan->u.write.buf, plan->u.write.len);
+ *	if (ret < 0)
+ *		return io_debug_io(-1);
+ *
+ *	plan->u.write.buf += ret;
+ *	plan->u.write.len -= ret;
+ *	return io_debug_io(plan->u.write.len == 0);
+ * }
  */
 int io_debug_io(int ret);
 
@@ -99,6 +127,10 @@ int io_debug_io(int ret);
  * Some routines, like io_break(), io_duplex() and io_wake() take an
  * io_plan, but they must not be applied immediately to the current
  * connection, so we call this first.
+ *
+ * Example:
+ * #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_plan_no_debug() ((io_plan_nodebug = true))