mirror of
https://github.com/yasuhirokimura/db18
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Yasuhiro KIMURA
241 lines
8.5 KiB
HTML
241 lines
8.5 KiB
HTML
<?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_STREAM->read()</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="blob.html" title="Chapter 13. External Files" />
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<link rel="prev" href="dbstream_close.html" title="DB_STREAM->close()" />
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<link rel="next" href="dbstream_size.html" title="DB_STREAM->size()" />
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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 18.1.40</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">
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<span xmlns="http://www.w3.org/1999/xhtml">DB_STREAM->read()</span>
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</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbstream_close.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 13.
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External Files
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbstream_size.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="dbstream_read"></a>
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<span>DB_STREAM->read()</span>
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</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.h>
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int
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DB_STREAM->read(DB_STREAM *dbs, DBT *data, db_off_t offset,
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u_int32_t size, u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DB_STREAM->read()</code> method reads
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<span class="bold"><strong>size</strong></span> bytes from the external file,
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starting at <span class="bold"><strong>offset</strong></span>, into the
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DBT <span class="bold"><strong>data</strong></span>.
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</p>
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<p>
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The stream is created using <a class="xref" href="dbstream.html" title="DBC->db_stream()">
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<span>DBC->db_stream()</span>
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</a>.
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</p>
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<p>
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Unless otherwise specified, the
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<code class="methodname">DB_STREAM->read()</code> <span>
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<span>
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method returns a non-zero error value on failure and 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="idm139753795524720"></a>Parameters</h3>
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</div>
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</div>
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</div>
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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="idm139753795512288"></a>data</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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The <span class="bold"><strong>data</strong></span> parameter is
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the <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> into which you
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want to place the data read using this method.
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</p>
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<p>
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Note that the data DBT must be set with one of the
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following flags, or this method will return an error:
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<a class="link" href="dbt.html#dbt_DB_DBT_MALLOC">DB_DBT_MALLOC</a>,
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<a class="link" href="dbt.html#dbt_DB_DBT_REALLOC">DB_DBT_REALLOC</a>,
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<a class="link" href="dbt.html#dbt_DB_DBT_USERMEM">DB_DBT_USERMEM</a>, or
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<a class="link" href="dbt.html#dbt_DB_DBT_APPMALLOC">DB_DBT_APPMALLOC</a>.
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</p>
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</div>
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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="idm139753795462432"></a>offset</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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The <span class="bold"><strong>offset</strong></span> parameter
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indicates the starting position, in bytes, from the
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beginning of the external file where you want the read to
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begin.
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</p>
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</div>
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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="idm139753795472832"></a>size</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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The <span class="bold"><strong>size</strong></span> parameter
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indicates the number of bytes to read.
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</p>
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</div>
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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="idm139753795460448"></a>flags</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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The <span class="bold"><strong>flags</strong></span> parameter must be set to 0.
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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="idm139753795556416"></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_STREAM->read()</code> <span>
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<span>
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method may fail and return one 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="idm139753795460640"></a>DB_BUFFER_SMALL</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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The DBT provided to this method was not configured
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appropriately, and so there is not enough space allocated
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for the bytes you are trying to read.
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</p>
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</div>
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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="idm139753795452816"></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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An invalid flag value or parameter was specified; or if the
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DBT was configured with
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<a class="link" href="dbt.html#dbt_DB_DBT_PARTIAL">DB_DBT_PARTIAL</a>.
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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="idm139753795461856"></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="blob.html" title="Chapter 13. External Files">DB_STREAM</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="idm139753795458576"></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="blob.html#bloblist" title="External Files and Related Methods">External Files 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="dbstream_close.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="blob.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="dbstream_size.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">
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<span>DB_STREAM->close()</span>
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</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">
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<span>DB_STREAM->size()</span>
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</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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