230 lines
7.0 KiB
HTML
230 lines
7.0 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>pthread_get_expiration_np()--Get Condition Expiration Time from Relative Time</title>
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Begin Header Records ========================================== -->
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<!-- NETMG2 SCRIPT A converted by B2H R4.1 (346) (CMS) by HOLTJM at -->
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<!-- RCHVMW2 on 29 Jan 1999 at 10:01:37 -->
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<!--File Edited November 2001 -->
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<!--End Header Records -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!-- Java sync-link -->
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>pthread_get_expiration_np()--Get Condition Expiration Time from Relative Time</h2>
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<div class="box" style="width: 70%;">
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<br>
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Syntax:
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<pre> #include <pthread.h>
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#include <time.h>
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int pthread_get_expiration_np(const struct timespec *delta,
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struct timespec *abstime); </pre>
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Service Program Name: QP0WPTHR<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE <br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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Signal Safe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>pthread_get_expiration_np</strong>() function computes an absolute time by adding the specified relative time (<em>delta</em>) to the current system time. The resulting absolute time output in the <em>abstime</em> parameter can be used as the expiration time in a call to <strong>pthread_cond_timedwait</strong>().</p>
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<p>The current system time is retrieved from the system clock.</p>
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<p><strong>Note:</strong> This function is not portable.</p>
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<br>
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<h3>Authorities and Locks</h3>
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<p>None.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong>delta</strong></dt>
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<dd>(Input) Elapsed time to add to the current system time</dd>
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<dt><strong>abstime</strong></dt>
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<dd>(Output) Address of the returned value representing the expiration time</dd>
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</dl>
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<br>
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<h3>Return Value</h3>
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<dl>
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<dt><strong>0</strong></dt>
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<dd><strong>pthread_get_expiration_np</strong>() was successful.</dd>
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<dt><strong>value</strong></dt>
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<dd><strong>pthread_get_expiration_np</strong>() was not successful. <em>value</em> is set to indicate the error condition.</dd>
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</dl>
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<br>
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<h3>Error Conditions</h3>
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<p>If <strong>pthread_get_expiration_np</strong>() was not successful, the error condition returned usually indicates one of the following errors. Under some conditions, the value returned could indicate an error other than those listed here.</p>
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<dl>
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<dt><em>[EINVAL]</em></dt>
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<dd><p>The value specified for the argument is not correct.</p></dd>
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</dl>
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<br>
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<h3>Related Information</h3>
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<ul>
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<li>The <<strong>pthread.h</strong>> header file. See <a href="rzah4hed.htm">Header files for Pthread functions</a>.<br><br></li>
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<li><a href="users_77.htm">pthread_cond_timedwait()</a>--Timed Wait for Condition</li>
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</ul>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<pre>#define _MULTI_THREADED
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#include <stdio.h>
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#include <qp0z1170.h>
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#include <time.h>
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#include <pthread.h>
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#include "check.h"
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/* For safe condition variable usage, must use a boolean predicate and */
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/* a mutex with the condition. */
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int workToDo = 0;
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pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
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pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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int failStatus=99;
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#define NTHREADS 2
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#define WAIT_TIME_SECONDS 3
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void *threadfunc(void *parm)
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{
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int rc;
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struct timespec delta;
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struct timespec abstime;
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int retries = 2;
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pthread_id_np_t tid;
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tid = pthread_getthreadid_np();
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rc = pthread_mutex_lock(&mutex);
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checkResults("pthread_mutex_lock()\n", rc);
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while (retries--) {
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delta.tv_sec = WAIT_TIME_SECONDS;
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delta.tv_nsec = 0;
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rc = pthread_get_expiration_np(&delta, &abstime);
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checkResults("pthread_get_expiration_np()\n", rc);
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while (!workToDo) {
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printf("Thread 0x%.8x %.8x blocked\n", tid);
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rc = pthread_cond_timedwait(&cond, &mutex, &abstime);
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if (rc != ETIMEDOUT) {
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printf("pthread_cond_timedwait() - expect timeout %d\n", rc);
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rc = pthread_mutex_unlock(&mutex);
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checkResults("pthread_mutex_lock()\n", rc);
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return __VOID(failStatus);
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}
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/* Since there is no code in this example to wake up any */
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/* thread on the condition variable, we know we are done */
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/* because we have timed out. */
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break;
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}
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printf("Wait timed out! tid=0x%.8x %.8x\n", tid);
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}
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rc = pthread_mutex_unlock(&mutex);
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checkResults("pthread_mutex_lock()\n", rc);
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return __VOID(0);
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}
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int main(int argc, char **argv)
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{
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int rc=0;
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int i;
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pthread_t threadid[NTHREADS];
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void *status;
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int results=0;
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printf("Enter Testcase - %s\n", argv[0]);
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printf("Create %d threads\n", NTHREADS);
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for(i=0; i<NTHREADS; ++i) {
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rc = pthread_create(&threadid[i], NULL, threadfunc, NULL);
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checkResults("pthread_create()\n", rc);
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}
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printf("Wait for threads and cleanup\n");
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for (i=0; i<NTHREADS; ++i) {
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rc = pthread_join(threadid[i], &status);
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checkResults("pthread_join()\n", rc);
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if (__INT(status) == failStatus) {
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printf("A thread failed!\n");
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results++;
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}
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}
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pthread_cond_destroy(&cond);
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pthread_mutex_destroy(&mutex);
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printf("Main completed\n");
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return results;
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}</pre>
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<p><strong>Output:</strong></p>
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<pre>Enter Testcase - QP0WTEST/TPGETEX0
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Create 2 threads
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Wait for threads and cleanup
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Thread 0x00000000 000002ab blocked
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Thread 0x00000000 000002ac blocked
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Wait timed out! tid=0x00000000 000002ab
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Thread 0x00000000 000002ab blocked
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Wait timed out! tid=0x00000000 000002ac
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Thread 0x00000000 000002ac blocked
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Wait timed out! tid=0x00000000 000002ab
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Wait timed out! tid=0x00000000 000002ac
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Main completed</pre>
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<hr>
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API introduced: V4R3
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> |
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<a href="rzah4mst.htm">Pthread APIs</a> |
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<a href="aplist.htm">APIs by category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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