[PATCH 3/4] shared/gatt-server: Improve long write session handling

[Łukasz Rymanowski <lukasz.rymanowski@xxxxxxxxxxx>]

With current implementation application layer has no idea when
long write session ends as it gets write callback with execute
write for each prepare write data.
With this patch, after data are completly received by gatt-server it
starts to call write callback in proper order with opcode
BT_ATT_OP_PREP_WRITE_REQ. After that, each characteristic gets
BT_ATT_OP_EXEC_WRITE_REQ so it knows that complete characteristic value
has been received and data can be marked as valid.
---
 src/shared/gatt-server.c | 78 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 73 insertions(+), 5 deletions(-)

diff --git a/src/shared/gatt-server.c b/src/shared/gatt-server.c
index 329f53f..931d619 100644
--- a/src/shared/gatt-server.c
+++ b/src/shared/gatt-server.c
@@ -104,6 +104,8 @@ struct bt_gatt_server {
 	struct queue *prep_queue;
 	unsigned int max_prep_queue_len;
 
+	struct queue *exec_queue;
+
 	struct async_read_op *pending_read_op;
 	struct async_write_op *pending_write_op;
 
@@ -137,6 +139,7 @@ static void bt_gatt_server_free(struct bt_gatt_server *server)
 		server->pending_write_op->server = NULL;
 
 	queue_destroy(server->prep_queue, prep_write_data_destroy);
+	queue_destroy(server->exec_queue, NULL);
 
 	gatt_db_unref(server->db);
 	bt_att_unref(server->att);
@@ -1155,10 +1158,61 @@ error:
 
 }
 
+static void exec_next_write(struct bt_gatt_server *server);
+
+static void exec_write_complete_cb(struct gatt_db_attribute *attr, int err,
+								void *user_data)
+{
+	struct bt_gatt_server *server = user_data;
+	uint16_t handle = gatt_db_attribute_get_handle(attr);
+
+	if (err) {
+		queue_remove_all(server->exec_queue, NULL, NULL, NULL);
+		bt_att_send_error_rsp(server->att, BT_ATT_OP_EXEC_WRITE_REQ,
+								handle, err);
+	}
+
+	exec_next_write(server);
+}
+
+static void exec_next_write(struct bt_gatt_server *server)
+{
+	uint16_t *handle;
+	struct gatt_db_attribute *attr;
+	bool status;
+	int err;
+
+	handle = queue_pop_head(server->exec_queue);
+	if (!handle) {
+		bt_att_send(server->att, BT_ATT_OP_EXEC_WRITE_RSP, NULL, 0,
+							NULL, NULL, NULL);
+	}
+
+	attr = gatt_db_get_attribute(server->db, PTR_TO_UINT(handle));
+	if (!attr) {
+		err = BT_ATT_ERROR_UNLIKELY;
+		goto error;
+	}
+
+	status = gatt_db_attribute_write(attr, 0, NULL , 0,
+						BT_ATT_OP_EXEC_WRITE_REQ,
+						server->att,
+						exec_write_complete_cb, server);
+	if (status)
+		return;
+
+	err = BT_ATT_ERROR_UNLIKELY;
+
+error:
+	queue_remove_all(server->exec_queue, NULL, NULL, NULL);
+	bt_att_send_error_rsp(server->att, BT_ATT_OP_EXEC_WRITE_REQ,
+						PTR_TO_UINT(handle), err);
+}
+
 static void exec_next_prep_write(struct bt_gatt_server *server,
 						uint16_t ehandle, int err);
 
-static void exec_write_complete_cb(struct gatt_db_attribute *attr, int err,
+static void prep_write_complete_cb(struct gatt_db_attribute *attr, int err,
 								void *user_data)
 {
 	struct bt_gatt_server *server = user_data;
@@ -1167,6 +1221,11 @@ static void exec_write_complete_cb(struct gatt_db_attribute *attr, int err,
 	exec_next_prep_write(server, handle, err);
 }
 
+static bool match_attribute_handle(const void *data, const void *match_data)
+{
+	return PTR_TO_UINT(data) == PTR_TO_UINT(match_data);
+}
+
 static void exec_next_prep_write(struct bt_gatt_server *server,
 						uint16_t ehandle, int err)
 {
@@ -1177,10 +1236,17 @@ static void exec_next_prep_write(struct bt_gatt_server *server,
 	if (err)
 		goto error;
 
+	/*
+	 *  Remember to which handles we need to send execute after reliable
+	 *  or long write session is done
+	 */
+	if (ehandle && !queue_find(server->exec_queue,	match_attribute_handle,
+							UINT_TO_PTR(ehandle)))
+		queue_push_tail(server->exec_queue, UINT_TO_PTR(ehandle));
+
 	next = queue_pop_head(server->prep_queue);
 	if (!next) {
-		bt_att_send(server->att, BT_ATT_OP_EXEC_WRITE_RSP, NULL, 0,
-							NULL, NULL, NULL);
+		exec_next_write(server);
 		return;
 	}
 
@@ -1192,9 +1258,9 @@ static void exec_next_prep_write(struct bt_gatt_server *server,
 
 	status = gatt_db_attribute_write(attr, next->offset,
 						next->value, next->length,
-						BT_ATT_OP_EXEC_WRITE_REQ,
+						BT_ATT_OP_PREP_WRITE_REQ,
 						server->att,
-						exec_write_complete_cb, server);
+						prep_write_complete_cb, server);
 
 	prep_write_data_destroy(next);
 
@@ -1396,6 +1462,8 @@ struct bt_gatt_server *bt_gatt_server_new(struct gatt_db *db,
 	server->max_prep_queue_len = DEFAULT_MAX_PREP_QUEUE_LEN;
 	server->prep_queue = queue_new();
 
+	server->exec_queue = queue_new();
+
 	if (!gatt_server_register_att_handlers(server)) {
 		bt_gatt_server_free(server);
 		return NULL;
-- 
2.5.0

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