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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>Decoding</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="Reed-Solomon Library Programming Interface" /><link rel="up" href="ch03.html" title="Chapter 3. Usage" /><link rel="prev" href="ch03s02.html" title="Encoding" /><link rel="next" href="ch03s04.html" title="Cleanup" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Decoding</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch03s02.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Usage</th><td width="20%" align="right"> <a accesskey="n" href="ch03s04.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Decoding"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id3027652"></a>Decoding</h2></div></div></div><div class="toc"><dl><dt><span class="sect2"><a href="ch03s03.html#id3027686">
Decoding with syndrome calculation, direct data correction
</a></span></dt><dt><span class="sect2"><a href="ch03s03.html#id3027704">
Decoding with syndrome given by hardware decoder, direct data correction
</a></span></dt><dt><span class="sect2"><a href="ch03s03.html#id3027723">
Decoding with syndrome given by hardware decoder, no direct data correction.
</a></span></dt></dl></div><p>
The decoder calculates the syndrome over
the given data length and the received parity symbols
and corrects errors in the data.
</p><p>
If a syndrome is available from a hardware decoder
then the syndrome calculation is skipped.
</p><p>
The correction of the data buffer can be suppressed
by providing a correction pattern buffer and an error
location buffer to the decoder. The decoder stores the
calculated error location and the correction bitmask
in the given buffers. This is useful for hardware
decoders which use a weird bit ordering scheme.
</p><p>
The databytes are expanded to the given symbol size
on the fly. There is no support for decoding continuous
bitstreams with a symbolsize != 8 at the moment. If
it is necessary it should be not a big deal to implement
such functionality.
</p><div class="sect2" title="Decoding with syndrome calculation, direct data correction"><div class="titlepage"><div><div><h3 class="title"><a id="id3027686"></a>
Decoding with syndrome calculation, direct data correction
</h3></div></div></div><pre class="programlisting">
/* Parity buffer. Size = number of roots */
uint16_t par[6];
uint8_t data[512];
int numerr;
/* Receive data */
.....
/* Receive parity */
.....
/* Decode 512 byte in data8.*/
numerr = decode_rs8 (rs_decoder, data8, par, 512, NULL, 0, NULL, 0, NULL);
</pre></div><div class="sect2" title="Decoding with syndrome given by hardware decoder, direct data correction"><div class="titlepage"><div><div><h3 class="title"><a id="id3027704"></a>
Decoding with syndrome given by hardware decoder, direct data correction
</h3></div></div></div><pre class="programlisting">
/* Parity buffer. Size = number of roots */
uint16_t par[6], syn[6];
uint8_t data[512];
int numerr;
/* Receive data */
.....
/* Receive parity */
.....
/* Get syndrome from hardware decoder */
.....
/* Decode 512 byte in data8.*/
numerr = decode_rs8 (rs_decoder, data8, par, 512, syn, 0, NULL, 0, NULL);
</pre></div><div class="sect2" title="Decoding with syndrome given by hardware decoder, no direct data correction."><div class="titlepage"><div><div><h3 class="title"><a id="id3027723"></a>
Decoding with syndrome given by hardware decoder, no direct data correction.
</h3></div></div></div><p>
Note: It's not necessary to give data and received parity to the decoder.
</p><pre class="programlisting">
/* Parity buffer. Size = number of roots */
uint16_t par[6], syn[6], corr[8];
uint8_t data[512];
int numerr, errpos[8];
/* Receive data */
.....
/* Receive parity */
.....
/* Get syndrome from hardware decoder */
.....
/* Decode 512 byte in data8.*/
numerr = decode_rs8 (rs_decoder, NULL, NULL, 512, syn, 0, errpos, 0, corr);
for (i = 0; i < numerr; i++) {
do_error_correction_in_your_buffer(errpos[i], corr[i]);
}
</pre></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch03s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch03.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch03s04.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Encoding </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Cleanup</td></tr></table></div></body></html>
