gossip: Added gossip store primitives

Signed-off-by: Christian Decker <decker.christian@gmail.com>

gossipd/Makefile

@@ -13,6 +13,7 @@ LIGHTNINGD_GOSSIP_CONTROL_OBJS := $(LIGHTNINGD_GOSSIP_CONTROL_SRC:.c=.o)
 
 # gossipd needs these:
 LIGHTNINGD_GOSSIP_HEADERS := gossipd/gen_gossip_wire.h \
+	gossipd/gossip_store.h				\
 	gossipd/handshake.h				\
 	gossipd/routing.h				\
 	gossipd/broadcast.h

gossipd/gossip.c

@@ -10,7 +10,6 @@
 #include <ccan/list/list.h>
 #include <ccan/mem/mem.h>
 #include <ccan/noerr/noerr.h>
-#include <ccan/read_write_all/read_write_all.h>
 #include <ccan/structeq/structeq.h>
 #include <ccan/take/take.h>
 #include <ccan/tal/str/str.h>

gossipd/gossip_store.c

@@ -0,0 +1,48 @@
+#include "gossip_store.h"
+
+#include <ccan/endian/endian.h>
+#include <ccan/read_write_all/read_write_all.h>
+#include <common/status.h>
+#include <fcntl.h>
+
+#define GOSSIP_STORE_FILENAME "gossip_store"
+
+struct gossip_store {
+	int read_fd, write_fd;
+};
+
+struct gossip_store *gossip_store_new(const tal_t *ctx)
+{
+	struct gossip_store *gs = tal(ctx, struct gossip_store);
+	gs->write_fd = open(GOSSIP_STORE_FILENAME, O_RDWR|O_APPEND|O_CREAT, 0600);
+	gs->read_fd = open(GOSSIP_STORE_FILENAME, O_RDONLY);
+	return gs;
+}
+
+void gossip_store_append(struct gossip_store *gs, const u8 *msg)
+{
+	u16 msglen = tal_len(msg);
+	beint16_t belen = cpu_to_be16(msglen);
+
+	write_all(gs->write_fd, &belen, sizeof(belen));
+	write_all(gs->write_fd, msg, msglen);
+}
+
+const u8 *gossip_store_read_next(const tal_t *ctx, struct gossip_store *gs)
+{
+	beint16_t belen;
+	u16 msglen;
+	u8 *msg;
+	if (!read_all(gs->read_fd, &belen, sizeof(belen)))
+		return NULL;
+
+	msglen = be16_to_cpu(belen);
+	msg = tal_arr(ctx, u8, msglen);
+
+	if (!read_all(gs->read_fd, msg, msglen))
+		status_failed(
+		    STATUS_FAIL_INTERNAL_ERROR,
+		    "Short read from gossip-store, expected lenght %d", msglen);
+
+	return msg;
+}

gossipd/gossip_store.h

@@ -0,0 +1,35 @@
+#ifndef GOSSIPD_GOSSIP_STORE_H
+#define GOSSIPD_GOSSIP_STORE_H
+
+#include "config.h"
+
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+
+/**
+ * gossip_store -- On-disk storage related information
+ */
+struct gossip_store;
+
+struct gossip_store *gossip_store_new(const tal_t *ctx);
+
+/**
+ * Write an incoming message to the `gossip_store`
+ *
+ * @param gs  The gossip_store to write to
+ * @param msg The message to write
+ * @return The newly created and initialized `gossip_store`
+ */
+void gossip_store_append(struct gossip_store *gs, const u8 *msg);
+
+/**
+ * Retrieve the next gossip message if any
+ *
+ * @param ctx The context to allocate the message from
+ * @param gs  The `gossip_store` to read from
+ * @return The gossip message allocated from `ctx`, `NULL` if no more messages are
+ *         available.
+ */
+const u8 *gossip_store_read_next(const tal_t *ctx, struct gossip_store *gs);
+
+#endif /* GOSSIPD_GOSSIP_STORE_H */