1.1. Overview

The modules is an XCAP client for OpenSER that can be used by other modules. It fetches XCAP elements, either documents or part of them, by sending HTTP GET requests. It also offers support for conditional queries. It uses libcurl library as a client-side HTTP transfer library.

The module offers an xcap client interface with general functions that allow requesting for an specific element from an xcap server. In addition to that it also offers the service of storing and update in database the documents it receives. In this case only an initial request to the module is required - xcapGetNewDoc-which is like a request to the module to handle from that point on the referenced document so as to promise that the newest version will always be present in database.

The update method is also configurable, either through periodical queries, applicable to any kind of xcap server or with an MI command that should be sent by the server upon an update.

The module is currently used by the presence_xml module, if the 'integrated_xcap_server' parameter is not set.

1.2. Dependencies

1.3. Exported Parameters

...
modparam("xcap_client", "db_url", 
	"mysql://openser:openserrw@192.168.2.132/openser")
...

...
modparam("xcap_client", "xcap_table", "xcaps")
...

...
modparam("xcap_client", "periodical_query", 0)
...

...
modparam("xcap_client", "query_period", 50)
...

...
:refreshXcapDoc:fifo_reply
/xcap-root/resource-lists/users/eyebeam/buddies-resource-list.xml
8000
_empty_line_
...
		

2.1. bind_xcap_api(xcap_api_t* api)

This function allows binding the needed functions.

...
typedef struct xcap_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_api_t;
...
			

2.2. 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.

2.3. 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_LIST, RLS_SERVICES and PIDF_MANIPULATION.

-the callback function has type :

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