NAME

       XPAInfoNew -  define an XPA info public access point

SYNOPSIS

         #include <xpa.h>

         XPA XPAInfoNew(char *class, char *name,
                        int (*info_callback)(),
                        void *info_data, char *info_mode);

DESCRIPTION

       [NB: this is an experimental interface, new to XPA 2.0, whose value and best use is
       evolving.]

       A program can register interest in receiving a short message about a particular topic from
       any other process that cares to send such a message.  Neither has to be an XPA server.
       For example, if a user starts to work with a new image file called new.fits, she might
       wish to alert interested programs about this new file by sending a short message using
       xpainfo:

         xpainfo IMAGEFILE /data/new.fits

       In this example, each process that has used the XPAInfoNew() call to register interest in
       messages associated with the identifier IMAGEFILE will have its info_callback() executed
       with the following calling sequence:

         int info_cb(void *info_data, void *call_data, char *paramlist)
         {
           XPA xpa = (XPA)call_data;
         }

       The arguments passed to this routine are equivalent to those sent in the send_callback()
       routine.  The main difference is that there is no buf sent to the info callback: this
       mechanism is meant for short announcement of messages of interest to many clients.

       The mode string is of the form: "key1=value1,key2=value2,..."  The following keywords are
       recognized:

         key           value           default         explanation
         ------        --------        --------        -----------
         acl           true/false      true            enable access control

       Because no buf is passed to this callback, the usual buf-related keywords are not
       applicable here.

       The information sent in the parameter list is arbitrary.  However, we envision sending
       information such as file names or XPA access points from which to collect more data.  Note
       that the xpainfo program and the XPAInfo() routine that cause the info_callback to execute
       do not wait for the callback to complete before returning.

SEE ALSO

       See xpa(7) for a list of XPA help pages