'\" t
.TH "BUXTON_REGISTER_NOTIFICATION" "3" "buxton 1" "buxton_register_notification"
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.SH "NAME"
buxton_register_notification, buxton_unregister_notification \-
Manage key-name notifications

.SH "SYNOPSIS"
.nf
\fB
#include <buxton.h>
\fR
.sp
\fB
int buxton_register_notification(BuxtonClient \fIclient\fB,
.br
                                 BuxtonKey \fIkey\fB,
.br
                                 BuxtonCallback \fIcallback\fB,
.br
                                 void *\fIdata\fB,
.br
                                 bool \fIsync\fB)
.sp
.br
int buxton_unregister_notification(BuxtonClient \fIclient\fB,
.br
                                   BuxtonKey \fIkey\fB,
.br
                                   BuxtonCallback \fIcallback\fB,
.br
                                   void *\fIdata\fB,
.br
                                   bool \fIsync\fB)
\fR
.fi

.SH "DESCRIPTION"
.PP
These functions are used to manage key\-name notifications on
\fIkey\fR for \fIclient\fR.

To register for notifications on a specific key\-name, the client
should call \fBbuxton_register_notification\fR(3)\&. Similarly, to
unregister for notifications, \fBbuxton_unregister_notification\fR(3)
can be used\&.

Both functions accept optional callback functions to register with
the daemon, referenced by the \fIcallback\fR argument; the callback
function is called upon completion of the operation\&. The \fIdata\fR
argument is a pointer to arbitrary userdata that is passed along to
the callback function\&.  Additonally, the \fIsync\fR argument
controls whether the operation should be synchronous or not; if
\fIsync\fR is false, the operation is asynchronous\&.

.SH "CODE EXAMPLE"
.nf
.sp
#define _GNU_SOURCE
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>

#include "buxton.h"

void notify_cb(BuxtonResponse response, void *data)
{
	bool *status = (bool *)data;
	BuxtonKey key;
	int32_t *value;
	char *name;

	if (buxton_response_status(response) != 0) {
		*status = false;
		return;
	}

	key = buxton_response_key(response);
	name = buxton_key_get_name(key);

	value = (int32_t*)buxton_response_value(response);
	if (value) {
		printf("key %s updated with new value %d\\n", name, *value);
	} else {
		printf("key %s was removed\\n", name);
	}

	buxton_key_free(key);
	free(value);
	free(name);
}

int main(void)
{
	BuxtonClient client;
	BuxtonKey key;
	bool status = true;
	struct pollfd pfd[1];
	int r;
	int fd;
	int repoll_count = 10;

	if ((fd = buxton_open(&client)) < 0) {
		printf("couldn't connect\\n");
		return -1;
	}

	key = buxton_key_create("hello", "test", NULL, INT32);
	if (!key) {
		return -1;
	}

	if (buxton_register_notification(client, key, notify_cb, &status, false)) {
		printf("set call failed to run\\n");
		return -1;
	}
repoll:
	pfd[0].fd = fd;
	pfd[0].events = POLLIN;
	pfd[0].revents = 0;
	r = poll(pfd, 1, 5000);

	if (r < 0) {
		printf("poll error\\n");
		return -1;
	} else if (r == 0) {
		if (repoll_count-- > 0) {
			goto out;
		}
		goto repoll;
	}

	if (!buxton_client_handle_response(client)) {
		printf("bad response from daemon\\n");
		return -1;
	}

	if (!status) {
		printf("Failed to register for notification\\n");
		return -1;
	}

	goto repoll;

out:
	if (buxton_unregister_notification(client, key, NULL, NULL, true)) {
		printf("Unregistration of notification failed\\n");
		return -1;
	}

	buxton_key_free(key);
	buxton_close(client);

	return 0;
}
.fi

.SH "RETURN VALUE"
.PP
Returns 0 on success, and a non\-zero value on failure\&.

.SH "COPYRIGHT"
.PP
Copyright 2014 Intel Corporation\&. License: Creative Commons
Attribution\-ShareAlike 3.0 Unported\s-2\u[1]\d\s+2, with exception
for code examples found in the \fBCODE EXAMPLE\fR section, which are
licensed under the MIT license provided in the \fIdocs/LICENSE.MIT\fR
file from this buxton distribution\&.

.SH "SEE ALSO"
.PP
\fBbuxton\fR(7),
\fBbuxtond\fR(8),
\fBbuxton\-api\fR(7)

.SH "NOTES"
.IP " 1." 4
Creative Commons Attribution\-ShareAlike 3.0 Unported
.RS 4
\%http://creativecommons.org/licenses/by-sa/3.0/
.RE