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.\" ========================================================================
.\"
.IX Title "xpainfonew 3"
.TH xpainfonew 3 "July 23, 2013" "version 2.1.15" "SAORD Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
\&\fBXPAInfoNew: define an \s-1XPA\s0 info public access point\fR
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  #include <xpa.h>
\&
\&  XPA XPAInfoNew(char *class, char *name,
\&                 int (*info_callback)(),
\&                 void *info_data, char *info_mode);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
[\s-1NB:\s0 this is an experimental interface, new to \s-1XPA\s0 2.0, whose value
and best use is evolving.]
.PP
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:
.PP
.Vb 1
\&  xpainfo IMAGEFILE /data/new.fits
.Ve
.PP
In this example, each process that has used the \fIXPAInfoNew()\fR call to
register interest in messages associated with the identifier \s-1IMAGEFILE\s0
will have its \fIinfo_callback()\fR executed with the following calling
sequence:
.PP
.Vb 4
\&  int info_cb(void *info_data, void *call_data, char *paramlist)
\&  {
\&    XPA xpa = (XPA)call_data;
\&  }
.Ve
.PP
The arguments passed to this routine are equivalent to those sent in
the \fIsend_callback()\fR 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.
.PP
The mode string is of the form: \*(L"key1=value1,key2=value2,...\*(R"
The following keywords are recognized:
.PP
.Vb 3
\&  key           value           default         explanation
\&  \-\-\-\-\-\-        \-\-\-\-\-\-\-\-        \-\-\-\-\-\-\-\-        \-\-\-\-\-\-\-\-\-\-\-
\&  acl           true/false      true            enable access control
.Ve
.PP
Because no buf is passed to this callback, the usual buf-related keywords
are not applicable here.
.PP
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 \fIXPAInfo()\fR routine that cause the info_callback to execute do not
wait for the callback to complete before returning.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
See xpa(n) for a list of \s-1XPA\s0 help pages