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261 lines
9.4 KiB
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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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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DbMultipleKeyDataBuilder</title>
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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="dbt.html" title="Chapter 4. The Dbt Handle" />
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<link rel="prev" href="dbmultipledatabuilder.html" title="DbMultipleDataBuilder" />
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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">DbMultipleKeyDataBuilder</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbmultipledatabuilder.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 4.
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The Dbt Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbmultiplerecnodatabuilder.html">Next</a></td>
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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="dbmultiplekeydatabuilder"></a>DbMultipleKeyDataBuilder</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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class DbMultipleKeyDataBuilder
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{
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public:
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DbMultipleKeyDataBuilder(Dbt &dbt);
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bool append(void *kbuf, size_t klen, void *dbuf, size_t dlen);
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bool reserve(void *&kdest, size_t klen, void *&ddest, size_t dlen);
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}; </pre>
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<p>
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This class builds a bulk buffer for use when the
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<a class="link" href="dbput.html#put_DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a>
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flag is specified to either the
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<a class="xref" href="dbput.html" title="Db::put()">Db::put()</a> or
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<a class="xref" href="dbdel.html" title="Db::del()">Db::del()</a> methods with the btree
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or hash access methods. The buffer in the
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> passed to the constructor is
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filled by calls to
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<a class="xref" href="dbmultiplekeydatabuilder.html#dbmultiplekeydatabuilder.append" title="DbMultipleKeyDataBuilder.append()">DbMultipleKeyDataBuilder.append()</a>
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or
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<a class="xref" href="dbmultiplekeydatabuilder.html#dbmultiplekeydatabuilder.reserve" title="DbMultipleKeyDataBuilder.reserve()">DbMultipleKeyDataBuilder.reserve()</a>.
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</p>
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<p>
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The constructor takes a <a class="xref" href="dbt.html" title="Chapter 4. The Dbt Handle">
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The Dbt Handle
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</a>
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that must be configured to contain a buffer managed by the application,
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with the <code class="literal">ulen</code> field set to the size of the buffer.
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</p>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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All instances of the bulk retrieval classes may be used only once,
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and to build the bulk buffer in the forward direction only.
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</p>
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</div>
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<p>
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Parameters are:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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<code class="literal">dbt</code>
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</p>
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<p>
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The <span class="bold"><strong>dbt</strong></span> parameter is a <a class="xref" href="dbt.html" title="Chapter 4. The Dbt Handle">
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The Dbt Handle
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</a> that must already be configured to contain a buffer managed by the application, with the <code class="literal">ulen</code> field set to the size of the buffer, which must be a multiple of 4.
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</p>
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</li>
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</ul>
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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="dbmultiplekeydatabuilder.append"></a>DbMultipleKeyDataBuilder.append()</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">DbMultipleKeyDataBuilder.append()</code>
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method copies a key/data pair to the end of the buffer.
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</p>
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<p>
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The <code class="methodname">DbMultipleKeyDataBuilder.append()</code>
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method returns <code class="literal">false</code> if the key/data
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pair does not fit in the buffer and <code class="literal">true</code>
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otherwise.
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</p>
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<p>
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Parameters are:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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<code class="literal">kbuf</code>
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</p>
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<p>
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A pointer to the key to be copied into the bulk buffer.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">klen</code>
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</p>
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<p>
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The number of bytes of the key to be copied.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">dbuf</code>
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</p>
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<p>
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A pointer to the data item to be copied into the bulk
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buffer.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">dlen</code>
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</p>
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<p>
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The number of bytes of the data item to be copied.
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</p>
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</li>
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</ul>
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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="dbmultiplekeydatabuilder.reserve"></a>DbMultipleKeyDataBuilder.reserve()</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">DbMultipleKeyDataBuilder.reserve()</code>
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method reserves space for the next key/data pair in the bulk
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buffer. Unlike the <code class="methodname">append()</code>, no data is
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actually copied into the bulk buffer by
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<code class="methodname">reserve()</code>: copying the data is the
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responsibility of the application.
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</p>
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<p>
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The <code class="methodname">DbMultipleKeyDataBuilder.reserve()</code>
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method returns <code class="literal">false</code> if the data does
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not fit in the buffer and <code class="literal">true</code> otherwise.
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</p>
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<p>
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Parameters are:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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<code class="literal">kdest</code>
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</p>
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<p>
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Set to a pointer to the position in the bulk buffer reserved for the key, if enough space is available.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">klen</code>
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</p>
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<p>
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The number of bytes to reserve for the key.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">ddest</code>
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</p>
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<p>
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Set to a pointer to the position in the bulk buffer reserved for the data item, if enough space is available.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">dlen</code>
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</p>
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<p>
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The number of bytes to reserve for the data item.
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</p>
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</li>
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</ul>
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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="id3611036"></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="dbmultiplebuilder.html" title="DbMultipleBuilder">DbMultipleBuilder</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="id3611149"></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="dbt.html#dbtlist" title="DBT and Bulk Operations">DBT and Bulk Operations</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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<td width="40%" align="left"><a accesskey="p" href="dbmultipledatabuilder.html">Prev</a> </td>
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<a accesskey="u" href="dbt.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="dbmultiplerecnodatabuilder.html">Next</a></td>
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<a accesskey="h" href="index.html">Home</a>
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