Define an \s-1xpa\s0 info public access point
#include <xpa.h>
XPA XPAInfoNew(char *class, char *name,
int (*info_callback)(),
void *info_data, char *info_mode);
[\s-1NB:\s0 this is an experimental interface, new to \s-1XPA\s0 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 \s-1XPA\s0 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 \s-1IMAGEFILE\s0 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: \*(L"key1=value1,key2=value2,...\*(R" 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 \s-1XPA\s0 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 xpa(7) for a list of \s-1XPA\s0 help pages