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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<title>BFILE C/C++ Objects and Functions</title>
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<link rel="up" href="bfile-extension.html" title="Appendix A. Using the BFILE Extension" />
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<div xmlns="" class="navheader">
<div class="libver">
<p>Library Version 11.2.5.3</p>
</div>
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">BFILE C/C++ Objects and Functions</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="bfile-sql.html">Prev</a> </td>
<th width="60%" align="center">Appendix A. Using the BFILE Extension</th>
<td width="20%" align="right"> </td>
</tr>
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="bfile-c"></a>BFILE C/C++ Objects and Functions</h2>
</div>
</div>
</div>
<div class="toc">
<dl>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_column_bfile">sqlite3_column_bfile</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_bfile_open">sqlite3_bfile_open</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_bfile_close">sqlite3_bfile_close</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_bfile_is_open">sqlite3_bfile_is_open</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_bfile_read">sqlite3_bfile_read</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_bfile_file_exists">sqlite3_bfile_file_exists</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_bfile_size">sqlite3_bfile_size</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="bfile-c.html#sqlite3_bfile_final">sqlite3_bfile_final</a>
</span>
</dt>
</dl>
</div>
<p>
The BFILE extension can optionally make available to you some
additional C language data types and functions for use with the
SQLite C/C++ interface. These are available to you only if
you take the proper steps when you compile Berkeley DB. See the
<em class="citetitle">Berkeley DB Installation and Build Guide</em> for more information.
</p>
<p>
Once enabled, the BFILE C extension makes the following new
structure available to you:
</p>
<pre class="programlisting">typedef struct sqlite3_bfile sqlite3_bfile;</pre>
<p>
This structure serves as the BFILE handle when you are using
the BFILE extension along with the SQLite C/C++ interface.
</p>
<p>
In addition to the new structure, you can also use the
following new C functions:
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_column_bfile"></a>sqlite3_column_bfile</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_column_bfile(sqlite3_stmt *pStmt, int iCol,
sqlite3_bfile **ppBfile); </pre>
<p>
Returns a result set from a query against a column of type
BFILE.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned and
the new BFILE handle is written to
<span class="bold"><strong>ppBfile</strong></span>. Otherwise,
<code class="literal">SQLITE_ERROR</code> is returned.
</p>
<p>
Parameters are:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<span class="bold"><strong>pStmt</strong></span>
</p>
<p>
Pointer to the prepared statement that the function
is evaluating. The statement is created
using <code class="literal">sqlite3_prepare_v2()</code>
or one of its variants.
</p>
<p>
If this statement does not point to a valid row,
the result is undefined.
</p>
</li>
<li>
<p>
<span class="bold"><strong>iCol</strong></span>
</p>
<p>
Index of the column for which information should be
returned. The left-most column of the result set
is index <code class="literal">0</code>. Use
<code class="literal">sqlite3_column_count()</code> to discover
the number of columns in the result set.
</p>
<p>
If the column index is out of range, the result is
undefined.
</p>
</li>
<li>
<p>
<span class="bold"><strong>ppBfile</strong></span>
</p>
<p>
The BFILE handle that you are using for the query.
This pointer is valid only until
<code class="literal">sqlite3_step()</code>,
<code class="literal">sqlite3_reset()</code> or
<code class="literal">sqlite3_finalize()</code> have been
called.
</p>
<p>
The memory space used to hold this handle is freed by
<a class="xref" href="bfile-c.html#sqlite3_bfile_final" title="sqlite3_bfile_final">sqlite3_bfile_final</a>
Do not pass these pointers to <code class="literal">sqlite3_free()</code>.
</p>
</li>
</ul>
</div>
<p>
This function can be called successfully only if all of the
following conditions are true. If any of the following are
not true, the result is undefined:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
The most recent call to
<code class="literal">sqlite3_step()</code> has returned
<code class="literal">SQLITE_ROW</code>.
</p>
</li>
<li>
<p>
Neither <code class="literal">sqlite3_reset()</code> nor
<code class="literal">sqlite3_finalize()</code> have been
called since the last time
<code class="literal">sqlite3_step()</code> was called.
</p>
</li>
<li>
<p>
<code class="literal">sqlite3_step()</code>,
<code class="literal">sqlite3_reset()</code> or
<code class="literal">sqlite3_finalize()</code> have not been
called from a different thread while this routine
is pending.
</p>
</li>
</ul>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_bfile_open"></a>sqlite3_bfile_open</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_bfile_open(sqlite3_bfile *pBfile); </pre>
<p>
Opens a file for incremental read.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned.
Otherwise, <code class="literal">SQLITE_ERROR</code> is returned.
</p>
<p>
To avoid a resource leak, every opened BFILE handle should
eventually be closed with the
<a class="xref" href="bfile-c.html#sqlite3_bfile_close" title="sqlite3_bfile_close">sqlite3_bfile_close</a>
function. Note that <span class="bold"><strong>pBfile</strong></span>
is always initialized such that it is always safe to invoke
<code class="literal">sqlite_bfile_close()</code> against it,
regardless of the success or failure of this function.
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_bfile_close"></a>sqlite3_bfile_close</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_bfile_close(sqlite3_bfile *pBfile); </pre>
<p>
Closes an open BFILE handle. The BFILE is closed
unconditionally. Even if this function returns an error,
the BFILE is still closed.
</p>
<p>
Calling this routine with a null pointer (such as would be
returned by failed call to sqlite3_column_bfile()) is a
harmless non-operation.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned.
Otherwise, <code class="literal">SQLITE_ERROR</code> is returned.
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_bfile_is_open"></a>sqlite3_bfile_is_open</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_bfile_is_open(sqlite3_bfile *pBfile, int *open); </pre>
<p>
Checks whether a BFILE handle is open. The
<code class="literal">open</code> parameter is set to 1 if the file
is open, otherwise it is 0.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned.
Otherwise, <code class="literal">SQLITE_ERROR</code> is returned.
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_bfile_read"></a>sqlite3_bfile_read</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_bfile_read(sqlite3_bfile *pBfile, void *oBuff, int nSize,
int iOffset, int *nRead); </pre>
<p>
This function is used to read data from an opened BFILE
handle into a caller-supplied buffer.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned, the
data that has been read is written to the output buffer,
<span class="bold"><strong>oBuff</strong></span>,
and the amount of data written to the buffer is recorded in
<span class="bold"><strong>nRead</strong></span>.
Otherwise, <code class="literal">SQLITE_ERROR</code> is returned.
</p>
<p>
Parameters are:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<span class="bold"><strong>pBfile</strong></span>
</p>
<p>
The BFILE handle from which the data is read.
</p>
<p>
This function only works on a BFILE handle which
has been created by a prior successful call to
<a class="xref" href="bfile-c.html#sqlite3_bfile_open" title="sqlite3_bfile_open">sqlite3_bfile_open</a>
and which has not been closed by
<a class="xref" href="bfile-c.html#sqlite3_bfile_close" title="sqlite3_bfile_close">sqlite3_bfile_close</a>.
Passing any other pointer in to this function
results in undefined and probably undesirable
behavior.
</p>
</li>
<li>
<p>
<span class="bold"><strong>oBuff</strong></span>
</p>
<p>
The buffer used to contain the data that is read
from <span class="bold"><strong>pBfile</strong></span>. It
must be at least <span class="bold"><strong>nSize</strong></span>
bytes in size.
</p>
</li>
<li>
<p>
<span class="bold"><strong>nSize</strong></span>
</p>
<p>
The amount of data, in bytes, to read from the
BFILE.
</p>
</li>
<li>
<p>
<span class="bold"><strong>iOffset</strong></span>
</p>
<p>
The offset from the beginning of the file where the
read operation is to begin.
</p>
</li>
<li>
<p>
<span class="bold"><strong>nRead</strong></span>
</p>
<p>
Contains the amount of data, in bytes, actually
written to buffer <span class="bold"><strong>oBuff</strong></span>
once the read operation is completed.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
The size of the BFILE can be determined using the
<a class="xref" href="bfile-c.html#sqlite3_bfile_size" title="sqlite3_bfile_size">sqlite3_bfile_size</a>
function.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_bfile_file_exists"></a>sqlite3_bfile_file_exists</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_bfile_file_exists(sqlite3_bfile *pBfile, int *exist); </pre>
<p>
Checks whether a BFILE exists. The
<code class="literal">exists</code> parameter is set to 1 if the file
is exists, otherwise it is 0.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned.
Otherwise, <code class="literal">SQLITE_ERROR</code> is returned.
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_bfile_size"></a>sqlite3_bfile_size</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_bfile_size(sqlite3_bfile *pBfile, off_t *size); </pre>
<p>
Returns the size of the BFILE, in bytes.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned, and
<span class="bold"><strong>size</strong></span> is set to the size of
the BFILE, in bytes.
Otherwise, <code class="literal">SQLITE_ERROR</code> is returned.
</p>
<p>
This function only works on a BFILE handle which
has been created by a prior successful call to
<a class="xref" href="bfile-c.html#sqlite3_column_bfile" title="sqlite3_column_bfile">sqlite3_column_bfile</a>
and which has not been finalized by
<a class="xref" href="bfile-c.html#sqlite3_bfile_final" title="sqlite3_bfile_final">sqlite3_bfile_final</a>.
Passing any other pointer in to this function
results in undefined and probably undesirable
behavior.
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="sqlite3_bfile_final"></a>sqlite3_bfile_final</h3>
</div>
</div>
</div>
<pre class="programlisting">int
sqlite3_bfile_final(sqlite3_bfile *pBfile); </pre>
<p>
Frees a BFILE handle.
</p>
<p>
On success, <code class="literal">SQLITE_OK</code> is returned.
Otherwise, <code class="literal">SQLITE_ERROR</code> is returned.
</p>
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