87 lines
3.4 KiB
HTML
87 lines
3.4 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_write</title>
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body>
|
||
|
|
|
||
|
|
<div class="para">
|
||
|
|
<h2>pf_write</h2>
|
||
|
|
<p>The pf_write function writes data to the file.</p>
|
||
|
|
<pre>
|
||
|
|
FRESULT pf_write (
|
||
|
|
const void* <span class="arg">buff</span>, <span class="c">/* [IN] Pointer to the data to be written */</span>
|
||
|
|
UINT <span class="arg">btw</span>, <span class="c">/* [IN] Number of bytes to write */</span>
|
||
|
|
UINT* <span class="arg">bw</span> <span class="c">/* [OUT] Pointer to the variable to return number of bytes written */</span>
|
||
|
|
);
|
||
|
|
</pre>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<div class="para">
|
||
|
|
<h4>Parameters</h4>
|
||
|
|
<dl class="par">
|
||
|
|
<dt>buff</dt>
|
||
|
|
<dd>Pointer to the data to be wtitten. A NULL specifies to finalize the current write operation.</dd>
|
||
|
|
<dt>btw</dt>
|
||
|
|
<dd>Number of bytes to write.</dd>
|
||
|
|
<dt>bw</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, write protected, 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 write function has some restrictions listed below:</p>
|
||
|
|
<ul>
|
||
|
|
<li>Cannot create file. Only existing file can be written.</li>
|
||
|
|
<li>Cannot expand file size.</li>
|
||
|
|
<li>Cannot update time stamp of the file.</li>
|
||
|
|
<li>Write operation can start/stop on the sector boundary.</li>
|
||
|
|
<li>Read-only attribute of the file cannot block write operation.</li>
|
||
|
|
</ul>
|
||
|
|
<p>File write operation must be done in following sequence.</p>
|
||
|
|
<ol>
|
||
|
|
<li><tt>pf_lseek(ofs);</tt> read/write pointer must be moved to sector bundary prior to initiate write operation or it will be rounded-down to the sector boundary.</li>
|
||
|
|
<li><tt>pf_write(buff, btw, &bw);</tt> Initiate write operation. Write first data to the file.</li>
|
||
|
|
<li><tt>pf_write(buff, btw, &bw);</tt> Write next data. Any other file function cannot be used while a write operation is in progress.</li>
|
||
|
|
<li><tt>pf_write(0, 0, &bw);</tt> Finalize the write operation. If read/write pointer is not on the sector boundary, left bytes in the sector will be filled with zero.</li>
|
||
|
|
</ol>
|
||
|
|
<p>The read/write pointer in the file system object advances in number of bytes written. After the function succeeded, <tt>*bw</tt> should be checked to detect end of file. In case of <tt>*bw < btw</tt>, it means the read/write pointer reached end of file during the write operation. Once a write operation is initiated, it must be finalized or the written data can be lost.</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<div class="para">
|
||
|
|
<h4>QuickInfo</h4>
|
||
|
|
<p>Available when <tt>_USE_WRITE == 1</tt>.</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<div class="para">
|
||
|
|
<h4>References</h4>
|
||
|
|
<p><tt><a href="open.html">pf_open</a>, <a href="sfatfs.html">FATFS</a></tt></p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<p class="foot"><a href="../00index_p.html">Return</a></p>
|
||
|
|
</body>
|
||
|
|
</html>
|