/wbudowane/mp3-wave/pff2/doc/pf/read.html

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  6. <link rel="up" title="Petit FatFs" href="../00index_p.html">

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  9. <title>Petit FatFs - pf_read</title>

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  14. <div class="para">

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  15. <h2>pf_read</h2>

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  16. <p>The pf_read function reads data from the file.</p>

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  17. <pre>

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  18. FRESULT pf_read (

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  19.   void* <em>Buffer</em>,       /* Pointer to the read buffer */

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  20.   WORD <em>ByteToRead</em>,    /* Number of bytes to read */

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  21.   WORD* <em>BytesRead</em>     /* Pointer to the variable to return number of bytes read */

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  22. );

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  23. </pre>

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  26. <div class="para">

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  27. <h4>Parameters</h4>

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  28. <dl class="par">

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  29. <dt>Buffer</dt>

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  30. <dd>Pointer to the buffer to store the read data. A NULL specifies the destination is an outgoing stream.</dd>

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  31. <dt>ByteToRead</dt>

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  32. <dd>Number of bytes to read.</dd>

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  33. <dt>BytesRead</dt>

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  34. <dd>Pointer to the WORD variable to return number of bytes read.</dd>

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  35. </dl>

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  40. <h4>Return Values</h4>

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  41. <dl class="ret">

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  42. <dt>FR_OK (0)</dt>

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  43. <dd>The function succeeded.</dd>

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  44. <dt>FR_DISK_ERR</dt>

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  45. <dd>The function failed due to an error in the disk function, a wrong FAT structure or an internal error.</dd>

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  46. <dt>FR_NOT_OPENED</dt>

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  47. <dd>The file has not been opened.</dd>

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  48. <dt>FR_NOT_ENABLED</dt>

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  49. <dd>The volume has not been mounted.</dd>

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  50. </dl>

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  55. <h4>Description</h4>

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  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 &lt; ByteToRead</tt>, it means the read pointer reached end of file during read operation.</p>

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  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>

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  58. </div>

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  61. <h4>QuickInfo</h4>

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  62. <p>Available when <tt>_USE_READ == 1</tt>.</p>

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  63. </div>

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  66. <div class="para">

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  67. <h4>References</h4>

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  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>

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  69. </div>

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  71. <p class="foot"><a href="../00index_p.html">Return</a></p>

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  72. </body>

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  73. </html>
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