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jeremybenn |
<!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=iso-8859-1">
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<meta http-equiv="Content-Style-Type" content="text/css">
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<link rel="up" title="FatFs" href="../00index_e.html">
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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">
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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* <em>FileObject</em>, /* Pointer to the file object structure */
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void* <em>Buffer</em>, /* Pointer to the buffer to store read data */
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UINT <em>ByteToRead</em>, /* Number of bytes to read */
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UINT* <em>ByteRead</em> /* Pointer to the variable to return number of bytes read */
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);
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</pre>
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</div>
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<div class="para">
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<h4>Parameters</h4>
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<dl class="par">
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<dt>FileObject</dt>
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<dd>Pointer to the open file object.</dd>
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<dt>Buffer</dt>
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<dd>Pointer to the buffer to store read data</dd>
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<dt>ByteToRead</dt>
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<dd>Number of bytes to read in range of UINT.</dd>
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<dt>ByteRead</dt>
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<dd>Pointer to the UINT variable to return number of bytes read. The value is always valid after the function call regardless of the result.</dd>
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</dl>
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</div>
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<div class="para">
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<h4>Return Values</h4>
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<dl class="ret">
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<dt>FR_OK (0)</dt>
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<dd>The function succeeded.</dd>
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<dt>FR_DENIED</dt>
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<dd>The function denied due to the file has been opened in non-read mode.</dd>
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<dt>FR_DISK_ERR</dt>
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<dd>The function failed due to an error in the disk function.</dd>
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<dt>FR_INT_ERR</dt>
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<dd>The function failed due to a wrong FAT structure or an internal error.</dd>
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<dt>FR_NOT_READY</dt>
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<dd>The disk drive cannot work due to no medium in the drive or any other reason.</dd>
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<dt>FR_INVALID_OBJECT</dt>
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<dd>The file object is invalid.</dd>
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</dl>
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</div>
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<div class="para">
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<h4>Description</h4>
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<p>The file pointer of the file object increases in number of bytes read. After the function succeeded, <tt>*ByteRead</tt> should be checked to detect the end of file. In case of <tt>*ByteRead < ByteToRead</tt>, it means the R/W pointer reached end of the file during read operation.</p>
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</div>
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<div class="para">
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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">
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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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