[Tarantool-patches] [PATCH v7 3/8] qsync: provide a binary form of syncro entries

[Cyrill Gorcunov <gorcunov@gmail.com>]

These msgpack entries will be needed to write them
down to a journal without involving txn engine. Same
time we would like to be able to allocate them on stack,
for this sake the binary form is predefined.

Part-of #5129

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 src/box/txn_limbo.c |  9 +++++++--
 src/box/xrow.c      | 41 ++++++++++++++++++-----------------------
 src/box/xrow.h      | 20 +++++++++++++++-----
 3 files changed, 40 insertions(+), 30 deletions(-)

diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
index 944161c30..ed8c10419 100644
--- a/src/box/txn_limbo.c
+++ b/src/box/txn_limbo.c
@@ -282,6 +282,11 @@ txn_limbo_write_synchro(struct txn_limbo *limbo, uint32_t type, int64_t lsn)
 	req.replica_id = limbo->instance_id;
 	req.lsn = lsn;
 
+	/*
+	 * This is a synchronous commit so we can
+	 * use body and row allocated on a stack.
+	 */
+	struct synchro_body_bin body;
 	struct xrow_header row;
 	struct request request = {
 		.header = &row,
@@ -291,8 +296,8 @@ txn_limbo_write_synchro(struct txn_limbo *limbo, uint32_t type, int64_t lsn)
 	if (txn == NULL)
 		goto rollback;
 
-	if (xrow_encode_synchro(&row, &txn->region, &req) != 0)
-		goto rollback;
+	xrow_encode_synchro(&row, &body, &req);
+
 	/*
 	 * This is not really a transaction. It just uses txn API
 	 * to put the data into WAL. And obviously it should not
diff --git a/src/box/xrow.c b/src/box/xrow.c
index 4b5d4356f..03a4abdda 100644
--- a/src/box/xrow.c
+++ b/src/box/xrow.c
@@ -893,35 +893,30 @@ xrow_encode_dml(const struct request *request, struct region *region,
 	return iovcnt;
 }
 
-int
-xrow_encode_synchro(struct xrow_header *row, struct region *region,
+void
+xrow_encode_synchro(struct xrow_header *row,
+		    struct synchro_body_bin *body,
 		    const struct synchro_request *req)
 {
-	size_t len = mp_sizeof_map(2) + mp_sizeof_uint(IPROTO_REPLICA_ID) +
-		     mp_sizeof_uint(req->replica_id) +
-		     mp_sizeof_uint(IPROTO_LSN) + mp_sizeof_uint(req->lsn);
-	char *buf = (char *)region_alloc(region, len);
-	if (buf == NULL) {
-		diag_set(OutOfMemory, len, "region_alloc", "buf");
-		return -1;
-	}
-	char *pos = buf;
-
-	pos = mp_encode_map(pos, 2);
-	pos = mp_encode_uint(pos, IPROTO_REPLICA_ID);
-	pos = mp_encode_uint(pos, req->replica_id);
-	pos = mp_encode_uint(pos, IPROTO_LSN);
-	pos = mp_encode_uint(pos, req->lsn);
+	/*
+	 * A map with two elements. We don't compress
+	 * numbers to have this structure constant in size,
+	 * which allows us to preallocate it on stack.
+	 */
+	body->m_body = 0x80 | 2;
+	body->k_replica_id = IPROTO_REPLICA_ID;
+	body->m_replica_id = 0xce;
+	body->v_replica_id = mp_bswap_u32(req->replica_id);
+	body->k_lsn = IPROTO_LSN;
+	body->m_lsn = 0xcf;
+	body->v_lsn = mp_bswap_u64(req->lsn);
 
 	memset(row, 0, sizeof(*row));
 
-	row->body[0].iov_base = buf;
-	row->body[0].iov_len = len;
-	row->bodycnt = 1;
-
 	row->type = req->type;
-
-	return 0;
+	row->body[0].iov_base = (void *)body;
+	row->body[0].iov_len = sizeof(*body);
+	row->bodycnt = 1;
 }
 
 int
diff --git a/src/box/xrow.h b/src/box/xrow.h
index 02dca74e5..20e82034d 100644
--- a/src/box/xrow.h
+++ b/src/box/xrow.h
@@ -240,16 +240,26 @@ struct synchro_request {
 	int64_t lsn;
 };
 
+/** Synchro request xrow's body in MsgPack format. */
+struct PACKED synchro_body_bin {
+	uint8_t m_body;
+	uint8_t k_replica_id;
+	uint8_t m_replica_id;
+	uint32_t v_replica_id;
+	uint8_t k_lsn;
+	uint8_t m_lsn;
+	uint64_t v_lsn;
+};
+
 /**
  * Encode synchronous replication request.
  * @param row xrow header.
- * @param region Region to use to encode the confirmation body.
+ * @param body Desination to use to encode the confirmation body.
  * @param req Request parameters.
- * @retval -1 on error.
- * @retval 0 success.
  */
-int
-xrow_encode_synchro(struct xrow_header *row, struct region *region,
+void
+xrow_encode_synchro(struct xrow_header *row,
+		    struct synchro_body_bin *body,
 		    const struct synchro_request *req);
 
 /**
-- 
2.26.2