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/*!
* \file
* \brief Definition of a CRC code class
* \author Tony Ottosson
*
* -------------------------------------------------------------------------
*
* IT++ - C++ library of mathematical, signal processing, speech processing,
* and communications classes and functions
*
* Copyright (C) 1995-2008 (see AUTHORS file for a list of contributors)
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* -------------------------------------------------------------------------
*/
#ifndef CRC_H
#define CRC_H
#include <itpp/base/vec.h>
#include <itpp/base/mat.h>
namespace itpp {
/*!
\ingroup fec
\brief Cyclic Redundancy Check Codes
This class will add the CRC bits after each input word. With b(i)
denoting the i-th input bit and p(i) the i-th parity check bit,
the order of the outbut bits will be:
\code [b(1), b(2), ..., b(k), p(1), p(2), ..., p(n-k)] \endcode
When the WCDMA CRC polynomials are used, this class will reverse
the order of the parity check bits in order to comply to the WCDMA
standard. Thus for the polynomials WCDMA-8, WCDMA-12, WCDMA-16,
and WCDMA-24 the output will be:
\code [b(1), b(2), ..., b(k), p(n-k), ..., p(2), p(1)] \endcode
Usage:
\code
CRC_Code crc(string("CRC-4"));
bvec bits = randb(10), coded_bits, decoded_bits;
bool error;
coded_bits = crc.encode(bits);
error = crc.decode(rec_bits, decoded_bits);
\endcode
*/
class CRC_Code {
public:
//! Default Constructor
CRC_Code() { reverse_parity = false; }
/*!
\brief Set CRC code to one of the standardpolynomials using the
string value.
\param code Possible values: CRC-4, CRC-7, CRC-8, CRC-12,
CRC-24, CRC-32, CCITT-4, CCITT-5, CCITT-6, CCITT-16, CCITT-32,
WCDMA-8, WCDMA-12, WCDMA-16, WCDMA-24, ATM-8, ANSI-16, SDLC-16
*/
CRC_Code(const std::string &code) { reverse_parity = false; set_code(code); }
//! Set an arbitary polynomial in bvec form. Start with highest order terms.
void set_generator(const bvec &poly);
//! Set CRC code to one of the standardpolynomials using the string value.
void set_code(const std::string &code);
//! Calulate the parity bits
void parity(const bvec &in_bits, bvec &out) const;
//! Return true if parity checks OK otherwise flase
bool check_parity(const bvec &coded_bits) const;
//! Calculate and add parity to the in_bits.
void encode(const bvec &in_bits, bvec &out) const;
//! Returns the in_bits vector with parity added
bvec encode(const bvec &in_bits) const;
//! Return true if parity checks OK otherwise flase. Also returns the message part in out.
bool decode(const bvec &coded_bits, bvec &out) const;
//! Return true if parity checks OK otherwise flase. Also returns the message part in bits.
bool decode(bvec &bits) const;
private:
bool reverse_parity;
bvec polynomial;
int no_parity;
};
} // namespace itpp
#endif // #ifndef CRC_H
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