74 lines
2.5 KiB
HTML
74 lines
2.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
|
|
<html lang="en">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<link rel="up" title="Petit FatFs" href="../00index_p.html">
|
|
<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default">
|
|
<link rel="stylesheet" href="../css_p.css" type="text/css" media="screen" title="ELM Default">
|
|
<title>Petit FatFs - pf_read</title>
|
|
</head>
|
|
|
|
<body>
|
|
|
|
<div class="para">
|
|
<h2>pf_read</h2>
|
|
<p>The pf_read function reads data from the file.</p>
|
|
<pre>
|
|
FRESULT pf_read (
|
|
void* <span class="arg">buff</span>, <span class="c">/* [OUT] Pointer to the read buffer */</span>
|
|
UINT <span class="arg">btr</span>, <span class="c">/* [IN] Number of bytes to read */</span>
|
|
UINT* <span class="arg">br</span> <span class="c">/* [OUT] Number of bytes read */</span>
|
|
);
|
|
</pre>
|
|
</div>
|
|
|
|
<div class="para">
|
|
<h4>Parameters</h4>
|
|
<dl class="par">
|
|
<dt>buff</dt>
|
|
<dd>Pointer to the buffer to store the read data. A NULL specifies the destination is an outgoing stream.</dd>
|
|
<dt>btr</dt>
|
|
<dd>Number of bytes to read.</dd>
|
|
<dt>br</dt>
|
|
<dd>Pointer to the variable to return number of bytes read.</dd>
|
|
</dl>
|
|
</div>
|
|
|
|
|
|
<div class="para">
|
|
<h4>Return Values</h4>
|
|
<dl class="ret">
|
|
<dt>FR_OK (0)</dt>
|
|
<dd>The function succeeded.</dd>
|
|
<dt>FR_DISK_ERR</dt>
|
|
<dd>The function failed due to a hard error in the disk function, a wrong FAT structure or an internal error.</dd>
|
|
<dt>FR_NOT_OPENED</dt>
|
|
<dd>The file has not been opened.</dd>
|
|
<dt>FR_NOT_ENABLED</dt>
|
|
<dd>The volume has not been mounted.</dd>
|
|
</dl>
|
|
</div>
|
|
|
|
|
|
<div class="para">
|
|
<h4>Description</h4>
|
|
<p>The file read/write pointer in the file system object advances in number of bytes read. After the function succeeded, <tt>*br</tt> should be checked to detect end of file. In case of <tt>*br < btr</tt>, it means the read pointer reached end of file during read operation.</p>
|
|
<p>If a NULL is given to the <tt class="arg">buff</tt>, the read bytes will be forwarded to the outgoing stream instead of the memory. The streaming function will be typically built-in the <tt>disk_readp()</tt> function.</p>
|
|
</div>
|
|
|
|
<div class="para">
|
|
<h4>QuickInfo</h4>
|
|
<p>Available when <tt>_USE_READ == 1</tt>.</p>
|
|
</div>
|
|
|
|
|
|
<div class="para">
|
|
<h4>References</h4>
|
|
<p><tt><a href="open.html">pf_open</a>, <a href="write.html">pf_write</a>, <a href="sfatfs.html">FATFS</a></tt></p>
|
|
</div>
|
|
|
|
<p class="foot"><a href="../00index_p.html">Return</a></p>
|
|
</body>
|
|
</html>
|