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author | William Joye <wjoye@cfa.harvard.edu> | 2017-10-26 16:45:12 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2017-10-26 16:45:12 (GMT) |
commit | 6054f36bb658916bd231b9002efb94444e2871c8 (patch) | |
tree | a815500ec9bf0e100f4075a825213605c382def0 /doc/pod/xpainfonew.pod | |
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Squashed 'xpa/' content from commit d6a54301
git-subtree-dir: xpa
git-subtree-split: d6a543018b46c5a6c47b5ff91e0e131549595ca6
Diffstat (limited to 'doc/pod/xpainfonew.pod')
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diff --git a/doc/pod/xpainfonew.pod b/doc/pod/xpainfonew.pod new file mode 100644 index 0000000..ae54f54 --- /dev/null +++ b/doc/pod/xpainfonew.pod @@ -0,0 +1,92 @@ +=pod + +=head1 NAME + + + +B<XPAInfoNew: define an XPA info public access point> + + + +=head1 SYNOPSIS + + + + + + #include <xpa.h> + + XPA XPAInfoNew(char *class, char *name, + int (*info_callback)(), + void *info_data, char *info_mode); + + + + + +=head1 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. + + + + +=head1 SEE ALSO + + + +See xpa(n) for a list of XPA help pages + + +=cut |