[ccan] / ccan / io / io.h

/* Licensed under LGPLv2.1+ - see LICENSE file for details */
#ifndef CCAN_IO_H
#define CCAN_IO_H
#include <ccan/tal/tal.h>
#include <ccan/typesafe_cb/typesafe_cb.h>
#include <stdbool.h>
#include <poll.h>
#include <unistd.h>

struct timers;
struct timer;
struct list_head;

/**
 * struct io_plan - a plan for input or output.
 *
 * Each io_conn has zero to two of these active at any time.
 */
struct io_plan;

/**
 * struct io_conn - a connection associated with an fd.
 */
struct io_conn;

/**
 * io_new_conn - create a new connection.
 * @ctx: the context to tal from (or NULL)
 * @fd: the file descriptor.
 * @init: the function to call for a new connection
 * @arg: the argument to @init.
 *
 * This creates a connection which owns @fd, it then calls
 * @init to initialize the connection, which sets up an io_plan.
 *
 * Returns NULL on error (and sets errno).
 *
 * Example:
 * // Dumb init function to print string and tell conn to close.
 * static struct io_plan *conn_init(struct io_conn *conn, const char *msg)
 * {
 *      printf("Created conn %p: %s", conn, msg);
 *      return io_close(conn);
 * }
 *
 * static void create_self_closing_pipe(void)
 * {
 *      int fd[2];
 *      struct io_conn *conn;
 *
 *      if (pipe(fd) != 0)
 *              exit(1);
 *      conn = io_new_conn(NULL, fd[0], conn_init, (const char *)"hi!");
 *      if (!conn)
 *              exit(1);
 * }
 */
#define io_new_conn(ctx, fd, init, arg)                                 \
        io_new_conn_((ctx), (fd),                                       \
                     typesafe_cb_preargs(struct io_plan *, void *,      \
                                         (init), (arg),                 \
                                         struct io_conn *conn),         \
                     (void *)(arg))

struct io_conn *io_new_conn_(const tal_t *ctx, int fd,
                             struct io_plan *(*init)(struct io_conn *, void *),
                             void *arg);

/**
 * io_set_finish - set finish function on a connection.
 * @conn: the connection.
 * @finish: the function to call when it's closed or fails.
 * @arg: the argument to @finish.
 *
 * @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().  The fd
 * will be closed before @finish is called.
 *
 * Example:
 * static void finish(struct io_conn *conn, const char *msg)
 * {
 *      // errno is not 0 after success, so this is a bit useless.
 *      printf("Conn %p closed with errno %i (%s)\n", conn, errno, msg);
 * }
 *
 * // Dumb init function to print string and tell conn to close.
 * static struct io_plan *conn_init(struct io_conn *conn, const char *msg)
 * {
 *      io_set_finish(conn, finish, msg);
 *      return io_close(conn);
 * }
 */
#define io_set_finish(conn, finish, arg)                                \
        io_set_finish_((conn),                                          \
                       typesafe_cb_preargs(void, void *,                \
                                           (finish), (arg),             \
                                           struct io_conn *),           \
                       (void *)(arg))
void io_set_finish_(struct io_conn *conn,
                    void (*finish)(struct io_conn *, void *),
                    void *arg);


/**
 * io_new_listener - create a new accepting listener.
 * @ctx: the context to tal from (or NULL)
 * @fd: the file descriptor.
 * @init: the function to call for a new connection
 * @arg: the argument to @init.
 *
 * When @fd becomes readable, we accept(), create a new connection,
 * (tal'ocated off @ctx) and pass that to init().  Note that if there is
 * an error on this file descriptor, it will be freed.
 *
 * Returns NULL on error (and sets errno).
 *
 * Example:
 * #include <sys/types.h>
 * #include <sys/socket.h>
 * #include <netdb.h>
 *
 * ...
 *
 * // 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(NULL, fd, conn_init, (const char *)"listened!");
 * }
 */
#define io_new_listener(ctx, fd, init, arg)                             \
        io_new_listener_((ctx), (fd),                                   \
                         typesafe_cb_preargs(struct io_plan *, void *,  \
                                             (init), (arg),             \
                                             struct io_conn *conn),     \
                         (void *)(arg))
struct io_listener *io_new_listener_(const tal_t *ctx, int fd,
                                     struct io_plan *(*init)(struct io_conn *,
                                                             void *),
                                     void *arg);

/**
 * io_close_listener - delete a listener.
 * @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(NULL, NULL);
 *              io_close_listener(l);
 *      }
 */
void io_close_listener(struct io_listener *listener);

/**
 * io_write - output plan to write data.
 * @conn: the connection that plan is for.
 * @data: the data buffer.
 * @len: the length to write.
 * @next: function to call output is done.
 * @arg: @next argument
 *
 * This updates the output plan, to write out a data buffer.  Once it's all
 * written, the @next function will be called: on an error, the finish
 * function is called instead.
 *
 * Note that the I/O may actually be done immediately.
 *
 * Example:
 * static struct io_plan *write_to_conn(struct io_conn *conn, const char *msg)
 * {
 *      // Write message, then close.
 *      return io_write(conn, msg, strlen(msg), io_close_cb, NULL);
 * }
 */
#define io_write(conn, data, len, next, arg)                            \
        io_write_((conn), (data), (len),                                \
                  typesafe_cb_preargs(struct io_plan *, void *,         \
                                      (next), (arg), struct io_conn *), \
                  (arg))
struct io_plan *io_write_(struct io_conn *conn,
                          const void *data, size_t len,
                          struct io_plan *(*next)(struct io_conn *, void *),
                          void *arg);

/**
 * io_read - input plan to read data.
 * @conn: the connection that plan is for.
 * @data: the data buffer.
 * @len: the length to read.
 * @next: function to call once input is done.
 * @arg: @next argument
 *
 * This creates a plan to read data into a buffer.  Once it's all
 * read, the @next function will be called: on an error, the finish
 * function is called instead.  If read() returns 0 (EOF) errno is set
 * to 0.
 *
 * Note that the I/O may actually be done immediately.
 *
 * Example:
 * static struct io_plan *read_from_conn(struct io_conn *conn, char *buf)
 * {
 *      // Read message, then close.
 *      return io_read(conn, buf, 12, io_close_cb, NULL);
 * }
 */
#define io_read(conn, data, len, next, arg)                             \
        io_read_((conn), (data), (len),                                 \
                 typesafe_cb_preargs(struct io_plan *, void *,          \
                                     (next), (arg), struct io_conn *),  \
                 (arg))
struct io_plan *io_read_(struct io_conn *conn,
                         void *data, size_t len,
                         struct io_plan *(*next)(struct io_conn *, void *),
                         void *arg);


/**
 * io_read_partial - input plan to read some data.
 * @conn: the connection that plan is for.
 * @data: the data buffer.
 * @maxlen: the maximum length to read
 * @lenp: set to the length actually read.
 * @next: function to call once input is done.
 * @arg: @next argument
 *
 * This creates a plan to read data into a buffer.  Once any data is
 * read, @len is updated and the @next function will be called: on an
 * error, the finish function is called instead.  If read() returns 0 (EOF)
 * errno is set to 0.
 *
 * Note that the I/O may actually be done immediately.
 *
 * Example:
 * struct buf {
 *      size_t len;
 *      char buf[12];
 * };
 *
 * static struct io_plan *dump(struct io_conn *conn, struct buf *b)
 * {
 *      printf("Partial read: '%*s'\n", (int)b->len, b->buf);
 *      free(b);
 *      return io_close(conn);
 * }
 *
 * static struct io_plan *read_part(struct io_conn *conn, struct buf *b)
 * {
 *      // Read message, then dump and close.
 *      return io_read_partial(conn, b->buf, sizeof(b->buf), &b->len, dump, b);
 * }
 */
#define io_read_partial(conn, data, maxlen, lenp, next, arg)            \
        io_read_partial_((conn), (data), (maxlen), (lenp),              \
                         typesafe_cb_preargs(struct io_plan *, void *,  \
                                             (next), (arg),             \
                                             struct io_conn *),         \
                         (arg))
struct io_plan *io_read_partial_(struct io_conn *conn,
                                 void *data, size_t maxlen, size_t *lenp,
                                 struct io_plan *(*next)(struct io_conn *,
                                                         void *),
                                 void *arg);

/**
 * io_write_partial - output plan to write some data.
 * @conn: the connection that plan is for.
 * @data: the data buffer.
 * @maxlen: the maximum length to write
 * @lenp: set to the length actually written.
 * @next: function to call once output is done.
 * @arg: @next argument
 *
 * This creates a plan to write data from a buffer.   Once any data is
 * written, @len is updated and the @next function will be called: on an
 * 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_partial(struct io_conn *conn, struct buf *b)
 * {
 *      printf("Only wrote: '%*s'\n", (int)b->len, b->buf);
 *      free(b);
 *      return io_close(conn);
 * }
 *
 * static struct io_plan *write_part(struct io_conn *conn, struct buf *b)
 * {
 *      // Write message, then dump and close.
 *      strcpy(b->buf, "Hello world");
 *      return io_write_partial(conn, b->buf, strlen(b->buf),
 *                              &b->len, show_partial, b);
 * }
 */
#define io_write_partial(conn, data, maxlen, lenp, next, arg)           \
        io_write_partial_((conn), (data), (maxlen), (lenp),             \
                          typesafe_cb_preargs(struct io_plan *, void *, \
                                              (next), (arg),            \
                                              struct io_conn *),        \
                          (arg))
struct io_plan *io_write_partial_(struct io_conn *conn,
                                  const void *data, size_t maxlen, size_t *lenp,
                                  struct io_plan *(*next)(struct io_conn *,
                                                          void*),
                                  void *arg);

/**
 * io_always - plan to immediately call next callback
 * @conn: the connection that plan is for.
 * @next: function to call.
 * @arg: @next argument
 *
 * Sometimes it's neater to plan a callback rather than call it directly;
 * for example, if you only need to read data for one path and not another.
 *
 * Example:
 * static struct io_plan *init_conn_with_nothing(struct io_conn *conn,
 *                                               void *unused)
 * {
 *      // Silly example: close on next time around loop.
 *      return io_always(conn, io_close_cb, NULL);
 * }
 */
#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,
                           struct io_plan *(*next)(struct io_conn *, void *),
                           void *arg);

/**
 * io_out_always - output plan to immediately call next callback
 * @conn: the connection that plan is for.
 * @next: function to call.
 * @arg: @next argument
 *
 * This is a variant of io_always() which uses the output plan; it only
 * matters if you are using io_duplex, and thus have two plans running at
 * once.
 */
#define io_out_always(conn, next, arg)                                  \
        io_out_always_((conn), typesafe_cb_preargs(struct io_plan *, void *, \
                                                   (next), (arg),       \
                                                   struct io_conn *),   \
                       (arg))

struct io_plan *io_out_always_(struct io_conn *conn,
                               struct io_plan *(*next)(struct io_conn *,
                                                       void *),
                               void *arg);

/**
 * io_sock_shutdown - start socket close process (flushes TCP sockets).
 * @conn: the connection the plan is for
 *
 * Simply closing a TCP socket can lose data; unfortunately you should
 * shutdown(SHUT_WR) and wait for the other side to see this and close.
 * Of course, you also need to set a timer, in case it doesn't (you may
 * already have some responsiveness timer, of course).
 *
 * On error, is equivalent to io_close().
 *
 * Example:
 * #include <ccan/timer/timer.h>
 *
 * // Timer infra needs wrapper to contain extra data.
 * struct timeout_timer {
 *    struct timer t;
 *    struct io_conn *conn;
 * };
 * static struct timers timers;
 *
 * static struct io_plan *flush_and_close(struct io_conn *conn)
 * {
 *    struct timeout_timer *timeout;
 *    // Freed if conn closes normally.
 *    timeout = tal(conn, struct timeout_timer);
 *    timeout->conn = conn;
 *    timeout->t = conn;
 *    timer_addrel(&timers, &timeout->t, time_from_sec(5));
 *    return io_sock_shutdown(conn);
 * }
 */
struct io_plan *io_sock_shutdown(struct io_conn *conn);

/**
 * io_connect - create an asynchronous connection to a listening socket.
 * @conn: the connection that plan is for.
 * @addr: where to connect.
 * @init: function to call once it's connected
 * @arg: @init argument
 *
 * This initiates a connection, and creates a plan for
 * (asynchronously) completing it.  Once complete, the @init function
 * will be called.
 *
 * Example:
 * #include <sys/types.h>
 * #include <sys/socket.h>
 * #include <netdb.h>
 *
 * // Write, then close socket.
 * static struct io_plan *init_connect(struct io_conn *conn,
 *                                     struct addrinfo *addrinfo)
 * {
 *      return io_connect(conn, addrinfo, io_close_cb, NULL);
 * }
 *
 * ...
 *
 *      int fd;
 *      struct addrinfo *addrinfo;
 *
 *      fd = socket(AF_INET, SOCK_STREAM, 0);
 *      getaddrinfo("localhost", "8111", NULL, &addrinfo);
 *      io_new_conn(NULL, fd, init_connect, addrinfo);
 */
struct addrinfo;
#define io_connect(conn, addr, next, arg)                               \
        io_connect_((conn), (addr),                                     \
                    typesafe_cb_preargs(struct io_plan *, void *,       \
                                        (next), (arg),                  \
                                        struct io_conn *),              \
                    (arg))

struct io_plan *io_connect_(struct io_conn *conn, const struct addrinfo *addr,
                            struct io_plan *(*next)(struct io_conn *, void *),
                            void *arg);

/**
 * io_duplex - set plans for both input and output.
 * @conn: the connection that plan is for.
 * @in: the input plan
 * @out: the output plan
 *
 * Most plans are either for input or output; io_duplex creates a plan
 * which does both.  This is often used in the init function to create
 * two independent streams, though it can be used once on any connection.
 *
 * Note that if either plan closes the connection, it will be closed.
 *
 * Example:
 * struct buf {
 *      char in[100];
 *      char out[100];
 * };
 *
 * 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), io_close_cb, b),
 *                       io_write(conn, b->out, sizeof(b->out), io_close_cb,b));
 * }
 */
struct io_plan *io_duplex(struct io_conn *conn,
                          struct io_plan *in_plan, struct io_plan *out_plan);

/**
 * 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.
 * @waitaddr: the address to wait on.
 * @next: function to call after waiting.
 * @arg: @next argument
 *
 * This leaves the input or output idle: io_wake(@waitaddr) will be
 * called later to restart the connection.
 *
 * Example:
 * // Silly example to wait then close.
 * static struct io_plan *wait(struct io_conn *conn, void *b)
 * {
 *      return io_wait(conn, b, io_close_cb, NULL);
 * }
 */
#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,
                         struct io_plan *(*next)(struct io_conn *, void *),
                         void *arg);


/**
 * io_out_wait - leave the output plan idle until something wakes us.
 * @conn: the connection that plan is for.
 * @waitaddr: the address to wait on.
 * @next: function to call after waiting.
 * @arg: @next argument
 *
 * io_wait() makes the input plan idle: if you're not using io_duplex it
 * doesn't matter which plan is waiting.  Otherwise, you may need to use
 * io_out_wait() instead, to specify explicitly that the output plan is
 * waiting.
 */
#define io_out_wait(conn, waitaddr, next, arg)                          \
        io_out_wait_((conn), (waitaddr),                                \
                     typesafe_cb_preargs(struct io_plan *, void *,      \
                                         (next), (arg),                 \
                                         struct io_conn *),             \
                     (arg))

struct io_plan *io_out_wait_(struct io_conn *conn,
                             const void *wait,
                             struct io_plan *(*next)(struct io_conn *, void *),
                             void *arg);

/**
 * io_wake - wake up any connections waiting on @wait
 * @waitaddr: the address to trigger.
 *
 * All io_conns who have returned io_wait() on @waitaddr will move on
 * to their next callback.
 *
 * Example:
 * static struct io_plan *wake_it(struct io_conn *conn, void *b)
 * {
 *      io_wake(b);
 *      return io_close(conn);
 * }
 */
void io_wake(const void *wait);

/**
 * io_break - return from io_loop()
 * @ret: non-NULL value to return from io_loop().
 *
 * This breaks out of the io_loop.  As soon as the current function
 * returns, any io_close()'d connections will have their 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)
 *      {
 *              io_break(msg);
 *              return io_close(conn);
 *      }
 */
void io_break(const void *ret);

/**
 * io_never - assert if callback is called.
 * @conn: the connection that plan is for.
 * @unused: an unused parameter to make this suitable for use as a callback.
 *
 * Sometimes you want to make it clear that a callback should never happen
 * (eg. for io_break).  This will assert() if called.
 *
 * Example:
 * static struct io_plan *break_out(struct io_conn *conn, void *unused)
 * {
 *      io_break(conn);
 *      // We won't ever return from io_break
 *      return io_never(conn, NULL);
 * }
 */
struct io_plan *io_never(struct io_conn *conn, void *unused);

/* FIXME: io_recvfrom/io_sendto */

/**
 * io_close - close a connection.
 * @conn: the connection to close.
 *
 * The connection is immediately freed: it doesn't have to be the
 * current connection and it doesn't need to be idle.  No more IO or
 * callbacks will occur, but if a function was added by io_set_finish()
 * it will be called with the current errno preserved.
 *
 * This is equivalent to tal_free(io_conn), except it returns an io_plan
 * for use in an io callback.
 *
 * Example:
 * static struct io_plan *close_on_timeout(struct io_conn *conn, const char *msg)
 * {
 *      printf("closing: %s\n", msg);
 *      return io_close(conn);
 * }
 */
struct io_plan *io_close(struct io_conn *conn);

/**
 * io_close_cb - helper callback to close a connection.
 * @conn: the connection.
 *
 * This is closes a connection; 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);

/**
 * io_close_taken_fd - close a connection, but remove the filedescriptor first.
 * @conn: the connection to take the file descriptor from and close.
 *
 * io_close closes the file descriptor underlying the io_conn; this version does
 * not.  Presumably you have used io_conn_fd() on it beforehand and will take
 * care of the fd yourself.
 *
 * Note that this also turns off O_NONBLOCK on the fd.
 *
 * Example:
 * static struct io_plan *steal_fd(struct io_conn *conn, int *fd)
 * {
 *      *fd = io_conn_fd(conn);
 *      printf("stealing fd %i and closing\n", *fd);
 *      return io_close_taken_fd(conn);
 * }
 */
struct io_plan *io_close_taken_fd(struct io_conn *conn);

/**
 * io_loop - process fds until all closed on io_break.
 * @timers - timers which are waiting to go off (or NULL for none)
 * @expired - an expired timer (can be NULL if @timers is)
 *
 * This is the core loop; it exits with the io_break() arg, or NULL if
 * all connections and listeners are closed, or with @expired set to an
 * expired timer (if @timers isn't NULL).
 *
 * Example:
 *      io_loop(NULL, NULL);
 */
void *io_loop(struct timers *timers, struct timer **expired);

/**
 * io_conn_fd - get the fd from a connection.
 * @conn: the connection.
 *
 * Sometimes useful, eg for getsockname().  Note that the fd is O_NONBLOCK.
 *
 * See Also:
 *      io_close_taken_fd
 */
int io_conn_fd(const struct io_conn *conn);

/**
 * io_plan_in_started - is this conn doing input I/O now?
 * @conn: the conn.
 *
 * This returns true if input I/O has been performed on the conn but
 * @next hasn't been called yet.  For example, io_read() may have done
 * a partial read.
 *
 * This can be useful if we want to terminate a connection only after
 * reading a whole packet: if this returns true, we would wait until
 * @next is called.
 */
bool io_plan_in_started(const struct io_conn *conn);

/**
 * io_plan_out_started - is this conn doing output I/O now?
 * @conn: the conn.
 *
 * This returns true if output I/O has been performed on the conn but
 * @next hasn't been called yet.  For example, io_write() may have done
 * a partial write.
 *
 * This can be useful if we want to terminate a connection only after
 * writing a whole packet: if this returns true, we would wait until
 * @next is called.
 */
bool io_plan_out_started(const struct io_conn *conn);

/**
 * io_flush_sync - (synchronously) complete any outstanding output.
 * @conn: the connection.
 *
 * This is generally used as an emergency escape, for example when we
 * want to write an error message on a socket before terminating, but it may
 * be in the middle of existing I/O.  We don't want to service any other
 * IO, either.
 *
 * This returns true if all pending output is complete, false on error.
 * The next callback is not called on the conn, but will be as soon as
 * io_loop() is called.
 *
 * See Also:
 *      io_close_taken_fd
 */
bool io_flush_sync(struct io_conn *conn);

/**
 * io_conn_exclusive - set/unset an io_conn to exclusively serviced
 * @conn: the connection
 * @exclusive: whether to be exclusive or not
 *
 * If any io_conn is set exclusive, then no non-exclusive io_conn (or
 * io_listener) will be serviced by io_loop().  If it's a io_duplex io_conn(),
 * then io_conn_exclusive() makes the read-side exclusive; io_conn_out_exclusive()
 * makes the write-side exclusive.
 *
 * This allows you to temporarily service only one (or several) fds.
 * For example, you might want to flush out one io_conn and not
 * receive any new connections or read any other input.
 *
 * Returns true if any exclusive io_conn remain, otherwise false.
 * (This is useful for checking your own logic: dangling exclusive io_conn
 * are dangerous!).
 */
bool io_conn_exclusive(struct io_conn *conn, bool exclusive);

/**
 * io_conn_out_exclusive - set/unset exclusive on the write-side of a duplex
 * @conn: the connection, post io_duplex
 * @exclusive: whether to be exclusive or not
 *
 * See io_conn_exclusive() above.
 */
bool io_conn_out_exclusive(struct io_conn *conn, bool exclusive);

/**
 * io_fd_block - helper to set an fd blocking/nonblocking.
 * @fd: the file descriptor
 * @block: true to set blocking, false to set non-blocking.
 *
 * Generally only fails is @fd isn't a valid file descriptor, otherwise
 * returns true.
 */
bool io_fd_block(int fd, bool block);

/**
 * io_time_override - override the normal call for time.
 * @nowfn: the function to call.
 *
 * io usually uses time_mono() internally, but this forces it
 * to use your function (eg. for debugging).  Returns the old
 * one.
 */
struct timemono (*io_time_override(struct timemono (*now)(void)))(void);

/**
 * io_poll_override - override the normal call for poll.
 * @pollfn: the function to call.
 *
 * io usually uses poll() internally, but this forces it to use your
 * function (eg. for debugging, suppressing fds, or polling on others unknown
 * to ccan/io).  Returns the old one.
 */
int (*io_poll_override(int (*poll)(struct pollfd *fds, nfds_t nfds, int timeout)))(struct pollfd *, nfds_t, int);

#endif /* CCAN_IO_H */