/wbudowane/mp3-wave/pff2/doc/pf/read.html
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1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> 2<html lang="en"> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> 5<meta http-equiv="Content-Style-Type" content="text/css"> 6<link rel="up" title="Petit FatFs" href="../00index_p.html"> 7<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default"> 8<link rel="stylesheet" href="../css_p.css" type="text/css" media="screen" title="ELM Default"> 9<title>Petit FatFs - pf_read</title> 10</head> 11 12<body> 13 14<div class="para"> 15<h2>pf_read</h2> 16<p>The pf_read function reads data from the file.</p> 17<pre> 18FRESULT pf_read ( 19 void* <em>Buffer</em>, /* Pointer to the read buffer */ 20 WORD <em>ByteToRead</em>, /* Number of bytes to read */ 21 WORD* <em>BytesRead</em> /* Pointer to the variable to return number of bytes read */ 22); 23</pre> 24</div> 25 26<div class="para"> 27<h4>Parameters</h4> 28<dl class="par"> 29<dt>Buffer</dt> 30<dd>Pointer to the buffer to store the read data. A NULL specifies the destination is an outgoing stream.</dd> 31<dt>ByteToRead</dt> 32<dd>Number of bytes to read.</dd> 33<dt>BytesRead</dt> 34<dd>Pointer to the WORD variable to return number of bytes read.</dd> 35</dl> 36</div> 37 38 39<div class="para"> 40<h4>Return Values</h4> 41<dl class="ret"> 42<dt>FR_OK (0)</dt> 43<dd>The function succeeded.</dd> 44<dt>FR_DISK_ERR</dt> 45<dd>The function failed due to an error in the disk function, a wrong FAT structure or an internal error.</dd> 46<dt>FR_NOT_OPENED</dt> 47<dd>The file has not been opened.</dd> 48<dt>FR_NOT_ENABLED</dt> 49<dd>The volume has not been mounted.</dd> 50</dl> 51</div> 52 53 54<div class="para"> 55<h4>Description</h4> 56<p>The read pointer in the file system object increases in number of bytes read. After the function succeeded, <tt>*BytesRead</tt> should be checked to detect end of file. In case of <tt>*BytesRead < ByteToRead</tt>, it means the read pointer reached end of file during read operation.</p> 57<p>If a NULL is given to the Buffer, the read bytes will be forwarded to the outgoing stream instead of the memory. The streaming function will be typically built-in the low level disk read function.</p> 58</div> 59 60<div class="para"> 61<h4>QuickInfo</h4> 62<p>Available when <tt>_USE_READ == 1</tt>.</p> 63</div> 64 65 66<div class="para"> 67<h4>References</h4> 68<p><tt><a href="open.html">pf_open</a>, <a href="write.html">pf_write</a>, <a href="sfatfs.html">FATFS</a></tt></p> 69</div> 70 71<p class="foot"><a href="../00index_p.html">Return</a></p> 72</body> 73</html>