1. add comments for app lib

2. fix bug of sensor_config_with_attr

core/iwasm/lib/app-libs/base/request.h

@@ -24,22 +24,108 @@
 extern "C" {
 #endif
 
-bool is_event_type(request_t * req);
+/**
+ * @typedef request_handler_f
+ *
+ * @brief Define the signature of callback function for API
+ * api_register_resource_handler() to handle request or for API
+ * api_subscribe_event() to handle event.
+ *
+ * @param request pointer of the request to be handled
+ *
+ * @see api_register_resource_handler
+ * @see api_subscribe_event
+ */
+typedef void (*request_handler_f)(request_t *request);
 
-typedef void (*request_handler_f)(request_t *);
-typedef void (*response_handler_f)(response_t *, void *);
+/**
+ * @typedef response_handler_f
+ *
+ * @brief Define the signature of callback function for API
+ * api_send_request() to handle response of a request.
+ *
+ * @param response pointer of the response to be handled
+ * @param user_data user data associated with the request which is set when
+ * calling api_send_request().
+ *
+ * @see api_send_request
+ */
+typedef void (*response_handler_f)(response_t *response, void *user_data);
 
-// Request APIs
-bool api_register_resource_handler(const char *url, request_handler_f);
+
+/*
+ *****************
+ * Request APIs
+ *****************
+ */
+
+/**
+ * @brief Register resource.
+ *
+ * @param url url of the resource
+ * @param handler callback function to handle the request to the resource
+ *
+ * @return true if success, false otherwise
+ */
+bool api_register_resource_handler(const char *url, request_handler_f handler);
+
+/**
+ * @brief Send request asynchronously.
+ *
+ * @param request pointer of the request to be sent
+ * @param response_handler callback function to handle the response
+ * @param user_data user data
+ */
 void api_send_request(request_t * request, response_handler_f response_handler,
         void * user_data);
 
+/**
+ * @brief Send response.
+ *
+ * @param response pointer of the response to be sent
+ *
+ * @par
+ * @code
+ * void res1_handler(request_t *request)
+ * {
+ *     response_t response[1];
+ *     make_response_for_request(request, response);
+ *     set_response(response, DELETED_2_02, 0, NULL, 0);
+ *     api_response_send(response);
+ * }
+ * @endcode
+ */
 void api_response_send(response_t *response);
 
-// event API
+
+/*
+ *****************
+ * Event APIs
+ *****************
+ */
+
+/**
+ * @brief Publish an event.
+ *
+ * @param url url of the event
+ * @param fmt format of the event payload
+ * @param payload payload of the event
+ * @param payload_len length in bytes of the event payload
+ *
+ * @return true if success, false otherwise
+ */
 bool api_publish_event(const char *url, int fmt, void *payload,
         int payload_len);
 
+
+/**
+ * @brief Subscribe an event.
+ *
+ * @param url url of the event
+ * @param handler callback function to handle the event.
+ *
+ * @return true if success, false otherwise
+ */
 bool api_subscribe_event(const char * url, request_handler_f handler);
 
 #ifdef __cplusplus