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