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/*!
* \file
* \brief Implementation 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
*
* -------------------------------------------------------------------------
*/
#include <itpp/comm/crc.h>
#include <itpp/base/specmat.h>
#include <itpp/base/matfunc.h>
namespace itpp {
void CRC_Code::set_generator(const bvec &poly)
{
//it_assert(poly(0) == 1 && poly(poly.size()-1) == 1, "CRC_Code::set_polynomial: not a valid polynomial");
it_assert(poly(0) == 1, "CRC_Code::set_polynomial: not a valid polynomial");
polynomial = poly;
no_parity = polynomial.size()-1;
}
//! \cond
std::string crccode[18][2] = {
{"CRC-4","1 1 1 1 1"},
{"CRC-7","1 1 0 1 0 0 0 1"},
{"CRC-8","1 1 1 0 1 0 1 0 1"},
{"CRC-12","1 1 0 0 0 0 0 0 0 1 1 1 1"},
{"CRC-24","1 1 0 0 0 0 0 0 0 0 1 0 1 0 0 0 1 0 0 0 0 0 0 0 1"},
{"CRC-32","1 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 1 1 0 0 0 1 1 1 0 0 0 1 0"},
{"CCITT-4","1 0 0 1 1"},
{"CCITT-5","1 1 0 1 0 1"},
{"CCITT-6","1 0 0 0 0 1 1"},
{"CCITT-16","1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1"},
{"CCITT-32","1 0 0 0 0 0 1 0 0 1 1 0 0 0 0 0 1 0 0 0 1 1 1 0 1 1 0 1 1 0 1 1 1"},
{"WCDMA-8","1 1 0 0 1 1 0 1 1"},
{"WCDMA-12","1 1 0 0 0 0 0 0 0 1 1 1 1"},
{"WCDMA-16","1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1"},
{"WCDMA-24","1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 1 1"},
{"ATM-8","1 0 0 0 0 0 1 1 1"},
{"ANSI-16","1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1"},
{"SDLC-16","1 1 0 1 0 0 0 0 0 1 0 0 1 0 1 1 1"},
};
//! \endcond
void CRC_Code::set_code(const std::string &code)
{
bvec poly;
for (int i=0; i<18;i++) {
if (crccode[i][0] == code)
poly = bvec(crccode[i][1]);
}
if ( (code=="WCDMA-8") || (code=="WCDMA-12") || (code=="WCDMA-16") || (code=="WCDMA-24") ) {
reverse_parity = true;
}
it_assert(poly.size()>0, "This CRC code doesn't exist in the tables");
set_generator(poly);
}
// Not optimized for speed!
void CRC_Code::parity(const bvec &in_bits, bvec &out) const
{
bvec temp = concat(in_bits, zeros_b(no_parity));
for (int i=0; i<temp.size()-polynomial.size()+1; i++) {
if (temp(i) == 1) {
temp.set_subvector(i,i+no_parity, temp(i,i+no_parity) + polynomial);
}
}
out = temp(temp.size()-no_parity,temp.size()-1);
if (reverse_parity) {
out = reverse( out );
}
}
// Not optimized for speed
bool CRC_Code::check_parity(const bvec &coded_bits) const
{
int n = coded_bits.size();
bvec temp;
if (reverse_parity) {
temp = concat( coded_bits.left(n-no_parity), reverse( coded_bits.right( no_parity ) ) );
} else {
temp = coded_bits;
}
for (int i=0; i<temp.size()-polynomial.size()+1; i++) {
if (temp(i) == 1) {
temp.set_subvector(i,i+no_parity, temp(i,i+no_parity) + polynomial);
}
}
if ( temp(temp.size()-no_parity,temp.size()-1) == zeros_b(no_parity) )
return true;
else
return false;
}
void CRC_Code::encode(const bvec &in_bits, bvec &out) const
{
bvec p;
parity(in_bits, p);
out = concat(in_bits, p);
}
bvec CRC_Code::encode(const bvec &in_bits) const
{
bvec temp;
encode(in_bits, temp);
return temp;
}
bool CRC_Code::decode(const bvec &coded_bits, bvec &out) const
{
out = coded_bits(0, coded_bits.size()-no_parity-1);
if (check_parity(coded_bits)) {
return true;
} else
return false;
}
bool CRC_Code::decode(bvec &coded_bits) const
{
//coded_bits = coded_bits(0, coded_bits.size()-no_parity-1); <-- OLD CODE
if (check_parity(coded_bits)) {
return true;
} else
return false;
}
} // namespace itpp
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