[PATCH v5 01/16] libs/guest: Reduce number of parts in write_split_record

[Frediano Ziglio <freddy77@gmail.com>]

From: Frediano Ziglio <frediano.ziglio@citrix.com>

Small optimization.
There's no much sense to split the header in 2 pieces, it will
just take more time and space to reassemble them in the final
buffer.
This also avoids truncating combined_length to 32 bit in case of
64 bit machines potentially avoiding following record_length check
(it could still be truncated writing it in xc_sr_rhdr structure
but the following check will catch it).
The function become more coherent with following read_record
function.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
--
Changes since v2:
- change prefix in subject.

Changes since v3:
- clarify commit message.

Changes since v4:
- added Reviewed-by;
- improved commit message.
---
 tools/libs/guest/xg_sr_common.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/libs/guest/xg_sr_common.c b/tools/libs/guest/xg_sr_common.c
index c7b3c6f3bc..9b2782b5cf 100644
--- a/tools/libs/guest/xg_sr_common.c
+++ b/tools/libs/guest/xg_sr_common.c
@@ -59,11 +59,11 @@ int write_split_record(struct xc_sr_context *ctx, struct xc_sr_record *rec,
     static const char zeroes[REC_ALIGN] = {};
 
     xc_interface *xch = ctx->xch;
-    typeof(rec->length) combined_length = rec->length + sz;
+    size_t combined_length = rec->length + sz;
     size_t record_length = ROUNDUP(combined_length, REC_ALIGN);
+    struct xc_sr_rhdr rhdr = { rec->type, combined_length };
     struct iovec parts[] = {
-        { &rec->type,       sizeof(rec->type) },
-        { &combined_length, sizeof(combined_length) },
+        { &rhdr,            sizeof(rhdr) },
         { rec->data,        rec->length },
         { buf,              sz },
         { (void *)zeroes,   record_length - combined_length },
-- 
2.43.0