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=utf-8"> 5<meta http-equiv="Content-Style-Type" content="text/css"> 6<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default"> 7<title>FatFs - f_read</title> 8</head> 9 10<body> 11 12<div class="para func"> 13<h2>f_read</h2> 14<p>The f_read function reads data from a file.</p> 15<pre> 16FRESULT f_read ( 17 FIL* <span class="arg">fp</span>, <span class="c">/* [IN] File object */</span> 18 void* <span class="arg">buff</span>, <span class="c">/* [OUT] Buffer to store read data */</span> 19 UINT <span class="arg">btr</span>, <span class="c">/* [IN] Number of bytes to read */</span> 20 UINT* <span class="arg">br</span> <span class="c">/* [OUT] Number of bytes read */</span> 21); 22</pre> 23</div> 24 25<div class="para arg"> 26<h4>Parameters</h4> 27<dl class="par"> 28<dt>fp</dt> 29<dd>Pointer to the open file object structure. If a null pointer is given, the function fails with <tt>FR_INVALID_OBJECT</tt>.</dd> 30<dt>buff</dt> 31<dd>Pointer to the buffer to store the read data.</dd> 32<dt>btr</dt> 33<dd>Number of bytes to read in range of <tt>UINT</tt> type. If the file needs to be read fast, it should be read in large chunk as possible.</dd> 34<dt>br</dt> 35<dd>Pointer to the variable in <tt>UINT</tt> type that receives number of bytes read. This value is always valid after the function call regardless of the function return code. If the return value is equal to <tt class="arg">btr</tt>, the function return code should be <tt>FR_OK</tt>.</dd> 36</dl> 37</div> 38 39 40<div class="para ret"> 41<h4>Return Values</h4> 42<p> 43<a href="rc.html#ok">FR_OK</a>, 44<a href="rc.html#de">FR_DISK_ERR</a>, 45<a href="rc.html#ie">FR_INT_ERR</a>, 46<a href="rc.html#dn">FR_DENIED</a>, 47<a href="rc.html#io">FR_INVALID_OBJECT</a>, 48<a href="rc.html#tm">FR_TIMEOUT</a> 49</p> 50</div> 51 52 53<div class="para desc"> 54<h4>Description</h4> 55<p>The function starts to read data from the file at the file offset pointed by read/write pointer of the file object. The read/write pointer advances as number of bytes read. After the function succeeded, <tt class="arg">*br</tt> should be checked to detect end of the file. In case of <tt class="arg">*br</tt> < <tt class="arg">btr</tt>, it means the read/write pointer hit end of the file during read operation.</p> 56</div> 57 58 59<div class="para comp"> 60<h4>QuickInfo</h4> 61<p>Always available.</p> 62</div> 63 64 65<div class="para use"> 66<h4>Example</h4> 67<p>Refer to the example in <tt>f_open</tt>.</p> 68</div> 69 70 71<div class="para ref"> 72<h4>See Also</h4> 73<p><tt><a href="open.html">f_open</a>, <a href="gets.html">fgets</a>, <a href="write.html">f_write</a>, <a href="close.html">f_close</a>, <a href="sfile.html">FIL</a></tt></p> 74</div> 75 76 77<p class="foot"><a href="../00index_e.html">Return</a></p> 78</body> 79</html> 80