net: lwm2m: Introduce attribute handling helper functions

Introduce LwM2M engine helper functions that allows to work with LwM2M
attributes outside of lwm2m_engine.c.

This is a groundwork for application/lwm2m-format content writer.

Signed-off-by: Robert Lubos <[email protected]>

Author: rlubos

subsys/net/lib/lwm2m/lwm2m_engine.c

@@ -1367,6 +1367,37 @@ static int path_to_objs(const struct lwm2m_obj_path *path,
 	return 0;
 }
 
+struct lwm2m_attr *lwm2m_engine_get_next_attr(const void *ref,
+					      struct lwm2m_attr *prev)
+{
+	struct lwm2m_attr *iter = (prev == NULL) ? write_attr_pool : prev + 1;
+	struct lwm2m_attr *result = NULL;
+
+	if (!PART_OF_ARRAY(write_attr_pool, iter)) {
+		return NULL;
+	}
+
+	while (iter < &write_attr_pool[ARRAY_SIZE(write_attr_pool)]) {
+		if (ref == iter->ref) {
+			result = iter;
+			break;
+		}
+
+		++iter;
+	}
+
+	return result;
+}
+
+const char *lwm2m_engine_get_attr_name(const struct lwm2m_attr *attr)
+{
+	if (attr->type >= NR_LWM2M_ATTR) {
+		return NULL;
+	}
+
+	return LWM2M_ATTR_STR[attr->type];
+}
+
 int lwm2m_engine_create_obj_inst(char *pathstr)
 {
 	struct lwm2m_obj_path path;
@@ -3486,6 +3517,44 @@ int lwm2m_get_or_create_engine_obj(struct lwm2m_message *msg,
 	return ret;
 }
 
+struct lwm2m_engine_obj *lwm2m_engine_get_obj(
+					const struct lwm2m_obj_path *path)
+{
+	if (path->level < LWM2M_PATH_LEVEL_OBJECT) {
+		return NULL;
+	}
+
+	return get_engine_obj(path->obj_id);
+}
+
+struct lwm2m_engine_obj_inst *lwm2m_engine_get_obj_inst(
+					const struct lwm2m_obj_path *path)
+{
+	if (path->level < LWM2M_PATH_LEVEL_OBJECT_INST) {
+		return NULL;
+	}
+
+	return get_engine_obj_inst(path->obj_id, path->obj_inst_id);
+}
+
+struct lwm2m_engine_res *lwm2m_engine_get_res(
+					const struct lwm2m_obj_path *path)
+{
+	struct lwm2m_engine_res *res = NULL;
+	int ret;
+
+	if (path->level < LWM2M_PATH_LEVEL_RESOURCE) {
+		return NULL;
+	}
+
+	ret = path_to_objs(path, NULL, NULL, &res, NULL);
+	if (ret < 0) {
+		return NULL;
+	}
+
+	return res;
+}
+
 static int do_write_op(struct lwm2m_message *msg,
 		       uint16_t format)
 {

subsys/net/lib/lwm2m/lwm2m_engine.h

@@ -65,6 +65,13 @@ int  lwm2m_get_or_create_engine_obj(struct lwm2m_message *msg,
 				    struct lwm2m_engine_obj_inst **obj_inst,
 				    uint8_t *created);
 
+struct lwm2m_engine_obj *lwm2m_engine_get_obj(
+					const struct lwm2m_obj_path *path);
+struct lwm2m_engine_obj_inst *lwm2m_engine_get_obj_inst(
+					const struct lwm2m_obj_path *path);
+struct lwm2m_engine_res *lwm2m_engine_get_res(
+					const struct lwm2m_obj_path *path);
+
 /* LwM2M context functions */
 int lwm2m_engine_context_close(struct lwm2m_ctx *client_ctx);
 void lwm2m_engine_context_init(struct lwm2m_ctx *client_ctx);
@@ -118,6 +125,12 @@ void lwm2m_firmware_set_update_result(uint8_t result);
 uint8_t lwm2m_firmware_get_update_result(void);
 #endif
 
+/* Attribute handling. */
+
+struct lwm2m_attr *lwm2m_engine_get_next_attr(const void *ref,
+					      struct lwm2m_attr *prev);
+const char *lwm2m_engine_get_attr_name(const struct lwm2m_attr *attr);
+
 /* Network Layer */
 int  lwm2m_socket_add(struct lwm2m_ctx *ctx);
 void lwm2m_socket_del(struct lwm2m_ctx *ctx);

subsys/net/lib/lwm2m/lwm2m_object.h

@@ -140,6 +140,12 @@
 struct lwm2m_engine_obj;
 struct lwm2m_message;
 
+#define LWM2M_PATH_LEVEL_NONE 0
+#define LWM2M_PATH_LEVEL_OBJECT 1
+#define LWM2M_PATH_LEVEL_OBJECT_INST 2
+#define LWM2M_PATH_LEVEL_RESOURCE 3
+#define LWM2M_PATH_LEVEL_RESOURCE_INST 4
+
 /* path representing object instances */
 struct lwm2m_obj_path {
 	uint16_t obj_id;