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/Makefile

@@ -46,6 +46,7 @@ LIGHTNINGD_LIB_SRC :=				\
 	lightningd/funding_tx.c			\
 	lightningd/htlc_tx.c			\
 	lightningd/key_derive.c			\
+	lightningd/msg_queue.c			\
 	lightningd/peer_failed.c		\
 	lightningd/utxo.c
 

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;
+}

lightningd/msg_queue.h

@@ -0,0 +1,21 @@
+/* Helper for simple message queues. */
+#ifndef LIGHTNING_LIGHTNINGD_MSG_QUEUE_H
+#define LIGHTNING_LIGHTNINGD_MSG_QUEUE_H
+#include "config.h"
+#include <ccan/io/io.h>
+#include <ccan/short_types/short_types.h>
+
+struct msg_queue {
+	const u8 **q;
+};
+
+void msg_queue_init(struct msg_queue *q, const tal_t *ctx);
+
+void msg_enqueue(struct msg_queue *q, const u8 *add);
+
+const u8 *msg_dequeue(struct msg_queue *q);
+
+#define msg_queue_wait(conn, q, next, arg) \
+	io_out_wait((conn), (q), (next), (arg))
+
+#endif /* LIGHTNING_LIGHTNINGD_MSG_QUEUE_H */