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HTML
189 lines
8.4 KiB
HTML
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Db::set_alloc()</title>
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<link rel="stylesheet" href="apiReference.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB C++ API Reference" />
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<link rel="up" href="db.html" title="Chapter 2. The Db Handle" />
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<link rel="prev" href="dbrename.html" title="Db::rename()" />
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<link rel="next" href="dbset_append_recno.html" title="Db::set_append_recno()" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Db::set_alloc()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbrename.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2.
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The Db Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbset_append_recno.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="dbset_alloc"></a>Db::set_alloc()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db_cxx.h>
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int
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Db::set_alloc(db_malloc_fcn_type app_malloc,
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db_realloc_fcn_type app_realloc,
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db_free_fcn_type app_free);</pre>
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<p>
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Set the allocation functions used by the
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> and
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<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> methods to allocate or free
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memory owned by the application.
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</p>
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<p>
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There are a number of interfaces in Berkeley DB where memory is
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allocated by the library and then given to the application. For
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example, the <a class="link" href="dbt.html#dbt_DB_DBT_MALLOC">DB_DBT_MALLOC</a>
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flag, when specified in the <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a>
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object, will cause the <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> methods to allocate and
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reallocate memory which then becomes the responsibility of the calling
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application. (See <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a>
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for more information.) Other examples are the Berkeley DB interfaces
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which return statistical information to the application:
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<a class="xref" href="dbstat.html" title="Db::stat()">Db::stat()</a>,
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<a class="xref" href="lockstat.html" title="DbEnv::lock_stat()">DbEnv::lock_stat()</a>,
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<a class="xref" href="logarchive.html" title="DbEnv::log_archive()">DbEnv::log_archive()</a>,
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<a class="xref" href="logstat.html" title="DbEnv::log_stat()">DbEnv::log_stat()</a>,
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<a class="xref" href="mempstat.html" title="DbEnv::memp_stat()">DbEnv::memp_stat()</a>,
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and <a class="xref" href="txnstat.html" title="DbEnv::txn_stat()">DbEnv::txn_stat()</a>. There is
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one method in Berkeley DB where memory is allocated by the application
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and then given to the library: <a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a>.
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</p>
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<p>
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On systems in which there may be multiple library versions of the
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standard allocation routines (notably Windows NT), transferring memory
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between the library and the application will fail because the Berkeley
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DB library allocates memory from a different heap than the application
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uses to free it. To avoid this problem, the
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<a class="xref" href="envset_alloc.html" title="DbEnv::set_alloc()">DbEnv::set_alloc()</a> and
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<code class="methodname">Db::set_alloc()</code> methods can be used to pass Berkeley DB references to
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the application's allocation routines.
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</p>
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<p>
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It is not an error to specify only one or two of the possible
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allocation function parameters to these interfaces; however, in that
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case the specified interfaces must be compatible with the standard
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library interfaces, as they will be used together. The functions
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specified must match the calling conventions of the ANSI C X3.159-1989
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(ANSI C) library routines of the same name.
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</p>
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<p>
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Because databases opened within Berkeley DB environments use the
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allocation interfaces specified to the environment, it is an error to
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attempt to set those interfaces in a database created within an
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environment.
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</p>
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<p>
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The <code class="methodname">Db::set_alloc()</code> method may not be called after the
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<a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a> method is called.
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</p>
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<p>
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The <code class="methodname">Db::set_alloc()</code> <span>
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<span>
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method either returns a non-zero error value or throws an
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exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3590845"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">Db::set_alloc()</code> <span>
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<span>
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method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
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exception, encapsulating one of the following non-zero errors, or return one
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of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3590995"></a>EINVAL</h4>
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</div>
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</div>
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</div>
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<p>
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If called in a database environment, or called after
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<a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a> was called; or if an
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invalid flag value or parameter was specified.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3590674"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a>
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</p>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3590849"></a>See Also</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
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</p>
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</div>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="dbrename.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="db.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="dbset_append_recno.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Db::rename() </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Db::set_append_recno()</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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