lightningd/msg_queue: helper for queues of messages/

Since they're short, we use a simple array.  This can be replaced later.

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

lightningd/msg_queue.c

@@ -0,0 +1,30 @@
+#include <lightningd/msg_queue.h>
+
+void msg_queue_init(struct msg_queue *q, const tal_t *ctx)
+{
+	q->q = tal_arr(ctx, const u8 *, 0);
+}
+
+void msg_enqueue(struct msg_queue *q, const u8 *add)
+{
+	size_t n = tal_count(q->q);
+	tal_resize(&q->q, n+1);
+	q->q[n] = add;
+
+	/* In case someone is waiting */
+	io_wake(q);
+}
+
+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;
+}