# &develguide;

The module exports a number of functions that allow selecting and retrieving an element from an xcap server and also registering a callback to be called when a MI command refreshXcapDoc is received and the document in question is retrieved.

## `bind_xcap_client_api(xcap_client_api_t* api)`

This function allows binding the needed functions.

### `xcap_client_api` structure

    ...
    typedef struct xcap_client_api {

    	/* xcap node selection and retrieving functions*/
    	xcap_get_elem_t get_elem;
    	xcap_nodeSel_init_t int_node_sel;
    	xcap_nodeSel_add_step_t add_step;
    	xcap_nodeSel_add_terminal_t add_terminal;
    	xcap_nodeSel_free_t free_node_sel;
    	xcapGetNewDoc_t getNewDoc; /* an initial request for the module
    	fo fetch this document that does not exist in xcap db table
    	and handle its update*/

    	/* function to register a callback to document changes*/
    	register_xcapcb_t register_xcb;
    }xcap_client_api_t;
    ...

## `get_elem`

Field type:

    ...
    typedef char* (*xcap_get_elem_t)(char* xcap_root,
    xcap_doc_sel_t* doc_sel, xcap_node_sel_t* node_sel);
    ...

This function sends a HTTP request and gets the specified information from the xcap server.

The parameters signification:

- xcap_root- the XCAP server address;

- doc_sel- structure with document selection info;

      Parameter type:
      ...
      typedef struct xcap_doc_sel
      {
      	str auid; /* application defined Unique ID*/
      	int type; /* the type of the path segment
      				after the AUID  which must either
      				be GLOBAL_TYPE (for "global") or
      				USERS_TYPE (for "users") */
      	str xid; /* the XCAP User Identifier
      				if type is USERS_TYPE */
      	str filename;
      }xcap_doc_sel_t;
      ...

- node_sel- structure with node selection info;

      Parameter type:
      ...
      typedef struct xcap_node_sel
      {
      	step_t* steps;
      	step_t* last_step;
      	int size;
      	ns_list_t* ns_list;
      	ns_list_t* last_ns;
      	int ns_no;

      }xcap_node_sel_t;

      typedef struct step
      {
      	str val;
      	struct step* next;
      }step_t;

      typedef struct ns_list
      {
      	int name;
      	str value;
      	struct ns_list* next;
      }ns_list_t;
      ...

  The node selector is represented like a list of steps that will be represented in the path string separated by '/' signs. The namespaces for the nodes are stored also in a list, as an association of name and value, where the value is to be included in the respective string val field of the step.

  To construct the node structure the following functions in the xcap_api structure should be used: 'int_node_sel', 'add_step' and if needed, 'add_terminal'.

  If the intention is to retrieve the whole document this argument must be NULL.

## `register_xcb`

Field type:

    ...
    typedef int (*register_xcapcb_t)(int types, xcap_cb f);
    ...

- 'types' parameter can have a combined value of PRES_RULES, RESOURCE_LISTS, RLS_SERVICES, OMA_PRES_RULES and PIDF_MANIPULATION.

-the callback function has type :

    ...
    typedef int (xcap_cb)(int doc_type, str xid, char* doc);
    ...