mirror of
https://github.com/yasuhirokimura/db18
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Yasuhiro KIMURA
248 lines
9.1 KiB
HTML
248 lines
9.1 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->write()</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_size.html" title="DB_STREAM->size()" />
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<link rel="next" href="envget_blob_dir.html" title="DB_ENV->get_ext_file_dir()" />
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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->write()</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_size.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="envget_blob_dir.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_write"></a>
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<span>DB_STREAM->write()</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->write(DB_STREAM *dbs, DBT *data, db_off_t offset,
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u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DB_STREAM->write()</code> method writes data
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to an existing external file object in the database. This method
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writes data contained in the <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
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<span class="bold"><strong>data</strong></span> to the external file stream.
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Data is written into the stream starting at the position indicated by
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<span class="bold"><strong>offset</strong></span>. The amount of data
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written is determined by the <code class="literal">size</code> field in the
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DBT.
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</p>
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<p>
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If this method writes data in the middle of the external file, it will
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overwrite existing data, instead of shifting it. If this method
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writes data to the end of the external file, the data is appended to
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the existing external file. You can determine how large an external
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file is using <a class="xref" href="dbstream_size.html" title="DB_STREAM->size()">
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<span>DB_STREAM->size()</span>
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</a>.
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</p>
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<p>
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To open a stream, use <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->write()</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="idm139753795459440"></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="idm139753795430528"></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> containing the
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data to be written to the external file. The amount of data
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to be written is determined by the DBT's
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<code class="literal">size</code> field.
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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="idm139753795419504"></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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identifies the position in the external file where the write
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operation will 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="idm139753795460832"></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
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set to 0 or the following value:
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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><a id="blobstream_DB_STREAM_SYNC_WRITE"></a>
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<code class="literal">DB_STREAM_SYNC_WRITE</code>
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</p>
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<p>
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A sync to disk operation is performed on the
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stream at the end of the write operation. By
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default, the sync is performed only when the
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stream is closed using <a class="xref" href="dbstream_close.html" title="DB_STREAM->close()">
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<span>DB_STREAM->close()</span>
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</a>. Note that
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this flag can also be specified when the stream is
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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>, in which case the sync
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behavior becomes the default behavior for this
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stream instance.
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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>
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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="idm139753795402656"></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->write()</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="idm139753795411840"></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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stream is read-only; or if the input DBT was
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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="idm139753795390704"></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="idm139753795388128"></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_size.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="envget_blob_dir.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->size()</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_ENV->get_ext_file_dir()</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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