wire/wire_sync: helper routines for direct read/write of messages.

Some of the simple daemons want to use this, as do the status messages.

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

wire/Makefile

@@ -4,15 +4,17 @@
 wire-wrongdir:
 	$(MAKE) -C .. wire-all
 
-WIRE_HEADERS := wire/wire.h
+WIRE_HEADERS := wire/wire.h wire/wire_sync.h
 WIRE_GEN_HEADERS := wire/gen_peer_wire.h wire/gen_onion_wire.h
 WIRE_GEN_SRC := wire/gen_peer_wire.c
 WIRE_GEN_ONION_SRC := wire/gen_onion_wire.c
-WIRE_SRC := wire/fromwire.c	\
+WIRE_SRC := wire/wire_sync.c			\
+		wire/fromwire.c			\
 		wire/towire.c
 
 WIRE_OBJS := $(WIRE_SRC:.c=.o) $(WIRE_GEN_SRC:.c=.o)
 WIRE_ONION_OBJS := $(WIRE_GEN_ONION_SRC:.c=.o)
+$(WIRE_OBJS): $(CCAN_HEADERS)
 
 # They may not have the bolts.
 BOLT_EXTRACT=$(BOLTDIR)/tools/extract-formats.py

wire/wire_sync.c

@@ -0,0 +1,26 @@
+#include "wire/wire_sync.h"
+#include <assert.h>
+#include <ccan/endian/endian.h>
+#include <ccan/read_write_all/read_write_all.h>
+
+bool wire_sync_write(int fd, const void *msg)
+{
+	be16 be_len = cpu_to_be16(tal_count(msg));
+
+	assert(be16_to_cpu(be_len) == tal_count(msg));
+	return write_all(fd, &be_len, sizeof(be_len))
+		&& write_all(fd, msg, tal_count(msg));
+}
+
+u8 *wire_sync_read(const tal_t *ctx, int fd)
+{
+	be16 be_len;
+	u8 *msg;
+
+	if (!read_all(fd, &be_len, sizeof(be_len)))
+		return NULL;
+	msg = tal_arr(ctx, u8, be16_to_cpu(be_len));
+	if (!read_all(fd, msg, be16_to_cpu(be_len)))
+		return tal_free(msg);
+	return msg;
+}

wire/wire_sync.h

@@ -0,0 +1,10 @@
+#ifndef LIGHTNING_WIRE_WIRE_SYNC_H
+#define LIGHTNING_WIRE_WIRE_SYNC_H
+#include "config.h"
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+
+bool wire_sync_write(int fd, const void *msg);
+u8 *wire_sync_read(const tal_t *ctx, int fd);
+
+#endif /* LIGHTNING_WIRE_WIRE_SYNC_H */