core-lightning/common/msg_queue.c
Rusty Russell 26dda57cc0 utils: make tal_arr_expand safer.
Christian and I both unwittingly used it in form:

	*tal_arr_expand(&x) = tal(x, ...)

Since '=' isn't a sequence point, the compiler can (and does!) cache
the value of x, handing it to tal *after* tal_arr_expand() moves it
due to tal_resize().

The new version is somewhat less convenient to use, but doesn't have
this problem, since the assignment is always evaluated after the
resize.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2019-01-15 12:01:38 +01:00

68 lines
1.2 KiB
C

#include <assert.h>
#include <common/msg_queue.h>
#include <common/utils.h>
#include <wire/wire.h>
struct msg_queue {
const u8 **q;
};
struct msg_queue *msg_queue_new(const tal_t *ctx)
{
struct msg_queue *q = tal(ctx, struct msg_queue);
q->q = tal_arr(q, const u8 *, 0);
return q;
}
static void do_enqueue(struct msg_queue *q, const u8 *add TAKES)
{
tal_arr_expand(&q->q, tal_dup_arr(q, u8, add, tal_count(add), 0));
/* In case someone is waiting */
io_wake(q);
}
void msg_enqueue(struct msg_queue *q, const u8 *add)
{
assert(fromwire_peektype(add) != MSG_PASS_FD);
do_enqueue(q, add);
}
void msg_enqueue_fd(struct msg_queue *q, int fd)
{
u8 *fdmsg = tal_arr(q, u8, 0);
towire_u16(&fdmsg, MSG_PASS_FD);
towire_u32(&fdmsg, fd);
do_enqueue(q, take(fdmsg));
}
const u8 *msg_dequeue(struct msg_queue *q)
{
size_t n = tal_count(q->q);
const u8 *msg;
if (!n)
return NULL;
msg = q->q[0];
memmove(q->q, q->q + 1, sizeof(*q->q) * (n-1));
tal_resize(&q->q, n-1);
return msg;
}
int msg_extract_fd(const u8 *msg)
{
const u8 *p = msg + sizeof(u16);
size_t len = tal_count(msg) - sizeof(u16);
if (fromwire_peektype(msg) != MSG_PASS_FD)
return -1;
return fromwire_u32(&p, &len);
}
void msg_wake(const struct msg_queue *q)
{
io_wake(q);
}