Commit 4f6d604c authored by Rusty Russell's avatar Rusty Russell

io: add io_flush_sync().

This is needed for emergency handling in lightningd: we want to output
a (fatal) error packet on the socket, but we don't want to do so in the middle
of another packet.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent bcca5169
......@@ -483,3 +483,37 @@ struct io_plan *io_set_plan(struct io_conn *conn, enum io_direction dir,
return plan;
}
bool io_flush_sync(struct io_conn *conn)
{
struct io_plan *plan = &conn->plan[IO_OUT];
bool ok;
/* Not writing? Nothing to do. */
if (plan->status != IO_POLLING)
return true;
/* Synchronous please. */
set_blocking(io_conn_fd(conn), true);
again:
switch (plan->io(conn->fd.fd, &plan->arg)) {
case -1:
ok = false;
break;
/* Incomplete, try again. */
case 0:
goto again;
case 1:
ok = true;
/* In case they come back. */
set_always(conn, IO_OUT, plan->next, plan->next_arg);
break;
default:
/* IO should only return -1, 0 or 1 */
abort();
}
set_blocking(io_conn_fd(conn), false);
return ok;
}
......@@ -673,6 +673,24 @@ void *io_loop(struct timers *timers, struct timer **expired);
*/
int io_conn_fd(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_time_override - override the normal call for time.
* @nowfn: the function to call.
......
#include <ccan/io/io.h>
/* Include the C files directly. */
#include <ccan/io/poll.c>
#include <ccan/io/io.c>
#include <ccan/tap/tap.h>
#include <sys/wait.h>
#include <stdio.h>
static size_t bytes_written;
/* Should be called multiple times, since only writes 1 byte. */
static int do_controlled_write(int fd, struct io_plan_arg *arg)
{
ssize_t ret;
ret = write(fd, arg->u1.cp, 1);
if (ret < 0)
return -1;
bytes_written += ret;
arg->u1.cp += ret;
arg->u2.s -= ret;
return arg->u2.s == 0;
}
static int do_error(int fd, struct io_plan_arg *arg)
{
errno = 1001;
return -1;
}
static struct io_plan *conn_wait(struct io_conn *conn, void *unused)
{
return io_wait(conn, conn, io_never, NULL);
}
static struct io_plan *init_conn_writer(struct io_conn *conn, const char *str)
{
struct io_plan_arg *arg = io_plan_arg(conn, IO_OUT);
arg->u1.const_vp = str;
arg->u2.s = strlen(str);
return io_set_plan(conn, IO_OUT, do_controlled_write, conn_wait, NULL);
}
static struct io_plan *init_conn_reader(struct io_conn *conn, void *dst)
{
/* Never actually succeeds. */
return io_read(conn, dst, 1000, io_never, NULL);
}
static struct io_plan *init_conn_error(struct io_conn *conn, void *unused)
{
io_plan_arg(conn, IO_OUT);
return io_set_plan(conn, IO_OUT, do_error, io_never, NULL);
}
int main(void)
{
int fd = open("/dev/null", O_RDWR);
const tal_t *ctx = tal(NULL, char);
struct io_conn *conn;
/* This is how many tests you plan to run */
plan_tests(9);
conn = io_new_conn(ctx, fd, init_conn_writer, "hello");
ok1(bytes_written == 0);
ok1(io_flush_sync(conn));
ok1(bytes_written == strlen("hello"));
/* This won't do anything */
ok1(io_flush_sync(conn));
ok1(bytes_written == strlen("hello"));
/* It's reading, this won't do anything. */
conn = io_new_conn(ctx, fd, init_conn_reader, ctx);
ok1(io_flush_sync(conn));
ok1(bytes_written == strlen("hello"));
/* Now test error state. */
conn = io_new_conn(ctx, fd, init_conn_error, ctx);
ok1(!io_flush_sync(conn));
ok1(errno == 1001);
tal_free(ctx);
/* This exits depending on whether all tests passed */
return exit_status();
}
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