common/per_per_state: generalize lightningd/peer_comm Part 1

Encapsulating the peer state was a win for lightningd; not surprisingly,
it's even more of a win for the other daemons, especially as we want
to add a little gossip information.

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

common/per_peer_state.c

@@ -0,0 +1,67 @@
+#include <assert.h>
+#include <ccan/fdpass/fdpass.h>
+#include <common/per_peer_state.h>
+#include <unistd.h>
+
+static void destroy_per_peer_state(struct per_peer_state *pps)
+{
+	if (pps->peer_fd != -1)
+		close(pps->peer_fd);
+	if (pps->gossip_fd != -1)
+		close(pps->gossip_fd);
+	if (pps->gossip_store_fd != -1)
+		close(pps->gossip_store_fd);
+}
+
+struct per_peer_state *new_per_peer_state(const tal_t *ctx,
+					  const struct crypto_state *cs)
+{
+	struct per_peer_state *pps = tal(ctx, struct per_peer_state);
+
+	pps->cs = *cs;
+	pps->peer_fd = pps->gossip_fd = pps->gossip_store_fd = -1;
+	tal_add_destructor(pps, destroy_per_peer_state);
+	return pps;
+}
+
+void per_peer_state_set_fds(struct per_peer_state *pps,
+			    int peer_fd, int gossip_fd, int gossip_store_fd)
+{
+	assert(pps->peer_fd == -1);
+	assert(pps->gossip_fd == -1);
+	assert(pps->gossip_store_fd == -1);
+	pps->peer_fd = peer_fd;
+	pps->gossip_fd = gossip_fd;
+	pps->gossip_store_fd = gossip_store_fd;
+}
+
+void per_peer_state_set_fds_arr(struct per_peer_state *pps, const int *fds)
+{
+	/* We expect 3 fds. */
+	assert(tal_count(fds) == 3);
+	per_peer_state_set_fds(pps, fds[0], fds[1], fds[2]);
+}
+
+void towire_per_peer_state(u8 **pptr, const struct per_peer_state *pps)
+{
+	towire_crypto_state(pptr, &pps->cs);
+}
+
+void per_peer_state_fdpass_send(int fd, const struct per_peer_state *pps)
+{
+	assert(pps->peer_fd != -1);
+	assert(pps->gossip_fd != -1);
+	assert(pps->gossip_store_fd != -1);
+	fdpass_send(fd, pps->peer_fd);
+	fdpass_send(fd, pps->gossip_fd);
+	fdpass_send(fd, pps->gossip_store_fd);
+}
+
+struct per_peer_state *fromwire_per_peer_state(const tal_t *ctx,
+					       const u8 **cursor, size_t *max)
+{
+	struct crypto_state cs;
+
+	fromwire_crypto_state(cursor, max, &cs);
+	return new_per_peer_state(ctx, &cs);
+}