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/*!
* \file
* \brief Definitions of a Reed-Solomon codec class
* \author Pal Frenger, Steve Peters and Adam Piatyszek
*
* -------------------------------------------------------------------------
*
* Copyright (C) 1995-2010 (see AUTHORS file for a list of contributors)
*
* This file is part of IT++ - a C++ library of mathematical, signal
* processing, speech processing, and communications classes and functions.
*
* IT++ is free software: you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any
* later version.
*
* IT++ is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along
* with IT++. If not, see <http://www.gnu.org/licenses/>.
*
* -------------------------------------------------------------------------
*/
#ifndef REEDSOLOMON_H
#define REEDSOLOMON_H
#include <itpp/base/vec.h>
#include <itpp/comm/galois.h>
#include <itpp/comm/channel_code.h>
namespace itpp
{
//---------------------- Reed-Solomon --------------------------------------
/*!
\ingroup fec
\brief Reed-Solomon Codes.
Uses the Berlkamp-Massey algorithm for decoding as described in: S. B. Wicker,
"Error Control Systems for digital communication and storage," Prentice Hall.
The code is \f$2^m\f$ - ary of length \f$2^m-1\f$ capable of correcting \f$t\f$ errors.
*/
class Reed_Solomon : public Channel_Code
{
public:
/*! Class constructor for the \f$2^m\f$ - ary, \f$t\f$ error correcting RS-code.
* The generator polynomial will be $g(x)=\prod_{i=0}^{2t-1}(x-\alpha^{b+i})$,
* where $\alpha$ is a root of the primitive polynomial of \c itpp::GF.
*/
Reed_Solomon(int in_m, int in_t, bool sys = false, int in_b = 1);
//! Destructor
virtual ~Reed_Solomon() { }
//! Encoder function.
virtual void encode(const bvec &uncoded_bits, bvec &coded_bits);
//! Encoder function.
virtual bvec encode(const bvec &uncoded_bits);
/*!
* \brief Decode the RS code bits. Return false if there has been any decoding failure.
*
* The \c coded_bits are block-wise decoded into \c decoded_message messages. If
* there has been any decoding failure, the function will return \c false.
* If this happened in the n-th block, then \c cw_isvalid(n) will be set
* to \c false (zero-indexed). In case of a systematic code the systematic bits will be
* extracted and presented in the corresponding block of \c decoded_message.
* This is better than just presenting zeros, which is done in case of a
* decoding failure of non-systematic codes.
*
* For erasure decoding the indices of erased positions need to be passed in \c erasure_positions
* as indices to the erased \fsymbol\f (not bit!).
*
*/
virtual bool decode(const bvec &coded_bits, const ivec &erasure_positions, bvec &decoded_message, bvec &cw_isvalid);
/*!
* \brief Decode the RS code bits. Return false if there has been any decoding failure.
*
* The \c coded_bits are block-wise decoded into \c decoded_message messages. If
* there has been any decoding failure, the function will return \c false.
* If this happened in the n-th block, then \c cw_isvalid(n) will be set
* to \c false (zero-indexed). In case of a systematic code the systematic bits will be
* extracted and presented in the corresponding block of \c decoded_message.
* This is better than just presenting zeros, which is done in case of a
* decoding failure of non-systematic codes.
*/
virtual bool decode(const bvec &coded_bits, bvec &decoded_message, bvec &cw_isvalid);
//! Decoder a \c bvec of coded data. This function is kept for backward compatibility. Better use \code bool decode(const bvec &coded_bits, bvec &decoded_message, bvec &cw_isvalid)\endcode.
virtual void decode(const bvec &coded_bits, bvec &decoded_bits);
//! Decoder a \c bvec of coded data. This function is kept for backward compatibility. Better use \code bool decode(const bvec &coded_bits, bvec &decoded_message, bvec &cw_isvalid)\endcode.
virtual bvec decode(const bvec &coded_bits);
// Soft-decision decoding is not implemented
virtual void decode(const vec &received_signal, bvec &output);
virtual bvec decode(const vec &received_signal);
//! Gets the rate of the RS-code.
virtual double get_rate() const { return static_cast<double>(k) / n; }
//! Dummy assignment operator - MSVC++ warning C4512
Reed_Solomon & operator=(const Reed_Solomon &) { return *this; }
protected:
/*! Internal encoder/decoder parameters
* @{ */
int m, t, k, n, q, b;
/*! @} */
//! The generator polynomial of the RS code
GFX g;
//! Whether or not the code is systematic
const bool systematic;
};
} // namespace itpp
#endif // #ifndef REEDSOLOMON_H