[PATCH v2 03/15] serialise: Add helpers for serialising unsigned integers

[David Gibson <david@gibson.dropbear.id.au>]

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>
---
 flow.c      | 10 ++++------
 serialise.c | 35 +++++++++++++++++++++++++++++++++++
 serialise.h |  7 +++++++
 3 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/flow.c b/flow.c
index 7d3c5ae6..81333dbc 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 (sewrite_var(fd, &count)) {
+	if (sewrite_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 (seread_var(fd, &count))
+	if (seread_u32(fd, &count))
 		return errno;
 
-	count = ntohl(count);
 	debug("Receiving %u flows", count);
 
 	if (!count)
diff --git a/serialise.c b/serialise.c
index 68054722..098ae35c 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 sewrite_buf(int fd, const void *buf, size_t len)
 	}
 	return 0;
 }
+
+/**
+ * seread_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
+ */
+/**
+ * sewrite_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 seread_u##bits(int fd, uint##bits##_t *val)			\
+	{								\
+		uint##bits##_t beval;					\
+		if (seread_var(fd, &beval) < 0)				\
+			return -1;					\
+		*val = be##bits##toh(beval);				\
+		return 0;						\
+	}								\
+	int sewrite_u##bits(int fd, uint##bits##_t val)			\
+	{								\
+		uint##bits##_t beval = htobe##bits(val);		\
+		return sewrite_var(fd, &beval);				\
+	}
+
+SERIALISE_UINT(32)
+
+#undef SERIALISE_UNIT
diff --git a/serialise.h b/serialise.h
index ec95287f..f2e0aa8d 100644
--- a/serialise.h
+++ b/serialise.h
@@ -7,6 +7,7 @@
 #define SERIALISE_H
 
 #include <stddef.h>
+#include <stdint.h>
 
 int seread_buf(int fd, void *buf, size_t len);
 int sewrite_buf(int fd, const void *buf, size_t len);
@@ -14,4 +15,10 @@ int sewrite_buf(int fd, const void *buf, size_t len);
 #define seread_var(fd_, var_)	(seread_buf((fd_), (var_), sizeof(*(var_))))
 #define sewrite_var(fd_, var_)	(sewrite_buf((fd_), (var_), sizeof(*(var_))))
 
+#define SERIALISE_UINT_DECL(bits)					\
+	int seread_u##bits(int fd, uint##bits##_t *val);		\
+	int sewrite_u##bits(int fd, uint##bits##_t val);
+
+SERIALISE_UINT_DECL(32)
+
 #endif /* _SERIALISE_H */
-- 
2.53.0