73 lines
2.3 KiB
HTML
73 lines
2.3 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=iso-8859-1">
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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">
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<h2>f_read</h2>
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<p>The f_read 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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BYTE* <em>Buffer</em>, // Pointer to the buffer to store read data
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WORD <em>ByteToRead</em>, // Number of bytes to read
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WORD* <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 valid file object structure.</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</dd>
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<dt>ByteRead</dt>
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<dd>Pointer to the WORD variable to return number of bytes read.</dd>
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</dt>
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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</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 write only mode.</dd>
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<dt>FR_ALIGN_ERROR</dt>
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<dd>The file has been opened in unbufferred mode but unaligned access was detected.</dd>
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<dt>FR_RW_ERROR</dt>
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<dd>Any error occured in low level disk I/O.</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_NOT_ENABLED</dt>
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<dd>FatFs module has not been enabled.</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 read/write pointer increases in number of bytes read. The <tt>ByteRead</tt> will be smaller than <tt>ByteToRead</tt> when the read pointer reached to end of the file or alignment error occured during the read operation. In unbufferred mode, last fractional bytes cannot be read due to <tt>FR_ALIGN_ERROR</tt>.</p>
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</div>
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<div class="para">
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<h4>References</h4>
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<p><tt><a href="open.html">f_open</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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