80 lines
2.8 KiB
HTML
80 lines
2.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<html lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta http-equiv="Content-Style-Type" content="text/css">
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<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default">
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<title>FatFs - f_read</title>
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</head>
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<body>
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<div class="para func">
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<h2>f_read</h2>
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<p>The f_read function reads data from a file.</p>
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<pre>
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FRESULT f_read (
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FIL* <span class="arg">fp</span>, <span class="c">/* [IN] File object */</span>
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void* <span class="arg">buff</span>, <span class="c">/* [OUT] Buffer to store read data */</span>
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UINT <span class="arg">btr</span>, <span class="c">/* [IN] Number of bytes to read */</span>
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UINT* <span class="arg">br</span> <span class="c">/* [OUT] Number of bytes read */</span>
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);
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</pre>
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</div>
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<div class="para arg">
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<h4>Parameters</h4>
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<dl class="par">
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<dt>fp</dt>
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<dd>Pointer to the open file object structure. If a null pointer is given, the function fails with <tt>FR_INVALID_OBJECT</tt>.</dd>
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<dt>buff</dt>
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<dd>Pointer to the buffer to store the read data.</dd>
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<dt>btr</dt>
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<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>
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<dt>br</dt>
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<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>
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</dl>
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</div>
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<div class="para ret">
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<h4>Return Values</h4>
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<p>
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<a href="rc.html#ok">FR_OK</a>,
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<a href="rc.html#de">FR_DISK_ERR</a>,
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<a href="rc.html#ie">FR_INT_ERR</a>,
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<a href="rc.html#dn">FR_DENIED</a>,
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<a href="rc.html#io">FR_INVALID_OBJECT</a>,
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<a href="rc.html#tm">FR_TIMEOUT</a>
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</p>
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</div>
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<div class="para desc">
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<h4>Description</h4>
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<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>
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</div>
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<div class="para comp">
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<h4>QuickInfo</h4>
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<p>Always available.</p>
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</div>
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<div class="para use">
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<h4>Example</h4>
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<p>Refer to the example in <tt>f_open</tt>.</p>
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</div>
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<div class="para ref">
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<h4>See Also</h4>
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<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>
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</div>
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<p class="foot"><a href="../00index_e.html">Return</a></p>
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</body>
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</html>
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