serialise: Add helpers for serialising unsigned integers

Add helpers to serialise/deserialise unsigned integers, handling endian
conversion so that the stream format is consistent regardless of host
endiannness.  Currently we only use this on one place: sending the number
of flows during migration.  We're going to have more use for this as we
add dynamic configuration updates, so these will become more useful.

For now we only need a 32-bit version, however define the functions with
a macro so we can easily add other integer widths when we need them.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

3 files changed, 46 insertions, 6 deletions

diff --git a/flow.c b/flow.c
index 25a6f1a..c84857b 100644
--- a/flow.c
+++ b/flow.c
@@ -1135,10 +1135,9 @@ int flow_migrate_source(struct ctx *c, const struct migrate_stage *stage,
 			count++;
 	}
 
-	count = htonl(count);
-	if (write_all_buf(fd, &count, sizeof(count))) {
+	if (write_u32(fd, count)) {
 		rc = errno;
-		err_perror("Can't send flow count (%u)", ntohl(count));
+		err_perror("Can't send flow count (%u)", count);
 		return flow_migrate_source_rollback(c, FLOW_MAX, rc);
 	}
 
@@ -1151,7 +1150,7 @@ int flow_migrate_source(struct ctx *c, const struct migrate_stage *stage,
 	debug("Stop listen()s");
 	fwd_listen_close(&c->fwd_in);
 
-	debug("Sending %u flows", ntohl(count));
+	debug("Sending %u flows", count);
 
 	if (!count)
 		return 0;
@@ -1221,10 +1220,9 @@ int flow_migrate_target(struct ctx *c, const struct migrate_stage *stage,
 
 	(void)stage;
 
-	if (read_all_buf(fd, &count, sizeof(count)))
+	if (read_u32(fd, &count))
 		return errno;
 
-	count = ntohl(count);
 	debug("Receiving %u flows", count);
 
 	if (!count)
diff --git a/serialise.c b/serialise.c
index f162eeb..944e741 100644
--- a/serialise.c
+++ b/serialise.c
@@ -13,7 +13,9 @@
  */
 
 #include <assert.h>
+#include <endian.h>
 #include <errno.h>
+#include <stdint.h>
 #include <unistd.h>
 
 #include "serialise.h"
@@ -86,3 +88,36 @@ int write_all_buf(int fd, const void *buf, size_t len)
 	}
 	return 0;
 }
+
+/**
+ * read_uXXX() - Receive a uXXX value from an fd
+ * @fd:		File descriptor to read from
+ * @valp:	Pointer to variable to update with read value
+ *
+ * Return: 0 on success, -1 on error
+ */
+/**
+ * write_uXXX() - Send a uXXX value to an fd
+ * @fd:		File descriptor to write to
+ * @val:	Value to send
+ *
+ * Return: 0 on success, -1 on error
+ */
+#define SERIALISE_UINT(bits)						\
+	int read_u##bits(int fd, uint##bits##_t *val)			\
+	{								\
+		uint##bits##_t beval;					\
+		if (read_all_buf(fd, &beval, sizeof(beval)) < 0)	\
+			return -1;					\
+		*val = be##bits##toh(beval);				\
+		return 0;						\
+	}								\
+	int write_u##bits(int fd, uint##bits##_t val)			\
+	{								\
+		uint##bits##_t beval = htobe##bits(val);		\
+		return write_all_buf(fd, &beval, sizeof(beval));	\
+	}
+
+SERIALISE_UINT(32)
+
+#undef SERIALISE_UINT
diff --git a/serialise.h b/serialise.h
index 251c772..a88f3de 100644
--- a/serialise.h
+++ b/serialise.h
@@ -7,8 +7,15 @@
 #define SERIALISE_H
 
 #include <stddef.h>
+#include <stdint.h>
 
 int read_all_buf(int fd, void *buf, size_t len);
 int write_all_buf(int fd, const void *buf, size_t len);
 
+#define SERIALISE_UINT_DECL(bits)					\
+	int read_u##bits(int fd, uint##bits##_t *val);			\
+	int write_u##bits(int fd, uint##bits##_t val);
+
+SERIALISE_UINT_DECL(32)
+
 #endif /* SERIALISE_H */