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<h2 class="title" style="clear: both"><a id="dbstream_read"></a>
<span>DbStream::read()</span>
</h2>
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<pre class="programlisting">#include <db_cxx.h>
int
DbStream::read(Dbt *data, db_off_t offset, u_int32_t size,
u_int32_t flags); </pre>
<p>
The <code class="methodname">DbStream::read()</code> method reads
<span class="bold"><strong>size</strong></span> bytes from the external file,
starting at <span class="bold"><strong>offset</strong></span>, into the
DBT <span class="bold"><strong>data</strong></span>.
</p>
<p>
The stream is created using <a class="xref" href="dbstream.html" title="Dbc::db_stream()">
<span>Dbc::db_stream()</span>
</a>.
</p>
<p>
Unless otherwise specified, the
<code class="methodname">DbStream::read()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idm139755608687536"></a>Parameters</h3>
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<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755608688784"></a>data</h4>
</div>
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</div>
<p>
The <span class="bold"><strong>data</strong></span> parameter is
the <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> into which you
want to place the data read using this method.
</p>
<p>
Note that the data DBT must be set with one of the
following flags, or this method will return an error:
<a class="link" href="dbt.html#dbt_DB_DBT_MALLOC">DB_DBT_MALLOC</a>,
<a class="link" href="dbt.html#dbt_DB_DBT_REALLOC">DB_DBT_REALLOC</a>,
<a class="link" href="dbt.html#dbt_DB_DBT_USERMEM">DB_DBT_USERMEM</a>, or
<a class="link" href="dbt.html#dbt_DB_DBT_APPMALLOC">DB_DBT_APPMALLOC</a>.
</p>
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<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755608693968"></a>offset</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>offset</strong></span> parameter
indicates the starting position, in bytes, from the
beginning of the external file where you want the read to
begin.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755608754368"></a>size</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>size</strong></span> parameter
indicates the number of bytes to read.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755608715232"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to 0.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idm139755608731888"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DbStream::read()</code> <span>
<span>
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
</span>
</span>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755608666896"></a>DB_BUFFER_SMALL</h4>
</div>
</div>
</div>
<p>
The Dbt provided to this method was not configured
appropriately, and so there is not enough space allocated
for the bytes you are trying to read.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm139755608682144"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
An invalid flag value or parameter was specified; or if the
Dbt was configured with
<a class="link" href="dbt.html#dbt_DB_DBT_PARTIAL">DB_DBT_PARTIAL</a>.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idm139755608665264"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="blob.html" title="Chapter 14. External Files">DbStream</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
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<div>
<h3 class="title"><a id="idm139755608684208"></a>See Also</h3>
</div>
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<p>
<a class="xref" href="blob.html#bloblist" title="External Files and Related Methods">External Files and Related Methods</a>
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<span>DbStream::close()</span>
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