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|
///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2016 Edouard Griffiths, F4EXB. //
// //
// Thanks to Sven Reifegerste: http://www.zorc.breitbandkatze.de/crc.html //
// //
// 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 as version 3 of the License, or //
// //
// 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 V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
///////////////////////////////////////////////////////////////////////////////////
#include "crc.h"
namespace DSDcc
{
const unsigned long CRC::PolyCCITT16 = 0x1021;
const unsigned long CRC::PolyDStar16 = 0x8408;
CRC::CRC(unsigned long polynomial,
int order,
unsigned long crcinit,
unsigned long crcxor,
int direct,
int refin,
int refout) :
m_order(order),
m_poly(polynomial),
m_direct(direct),
m_crcinit(crcinit),
m_crcxor(crcxor),
m_refin(refin),
m_refout(refout)
{
m_crcmask = ((((unsigned long) 1 << (m_order - 1)) - 1) << 1) | 1;
m_crchighbit = (unsigned long) 1 << (m_order - 1);
generate_crc_table();
init();
}
CRC::~CRC()
{
}
unsigned long CRC::reflect(unsigned long crc, int bitnum)
{
// reflects the lower 'bitnum' bits of 'crc'
unsigned long i, j = 1, crcout = 0;
for (i = (unsigned long) 1 << (bitnum - 1); i; i >>= 1)
{
if (crc & i)
crcout |= j;
j <<= 1;
}
return (crcout);
}
void CRC::generate_crc_table()
{
// make CRC lookup table used by table algorithms
int i, j;
unsigned long bit, crc;
for (i = 0; i < 256; i++)
{
crc = (unsigned long) i;
if (m_refin)
crc = reflect(crc, 8);
crc <<= m_order - 8;
for (j = 0; j < 8; j++)
{
bit = crc & m_crchighbit;
crc <<= 1;
if (bit)
crc ^= m_poly;
}
if (m_refin)
crc = reflect(crc, m_order);
crc &= m_crcmask;
m_crctab[i] = crc;
}
}
void CRC::init()
{
unsigned int i;
unsigned long bit, crc;
if (!m_direct)
{
m_crcinit_nondirect = m_crcinit;
crc = m_crcinit;
for (i = 0; i < m_order; i++)
{
bit = crc & m_crchighbit;
crc <<= 1;
if (bit)
crc ^= m_poly;
}
crc &= m_crcmask;
m_crcinit_direct = crc;
}
else
{
m_crcinit_direct = m_crcinit;
crc = m_crcinit;
for (i = 0; i < m_order; i++)
{
bit = crc & 1;
if (bit)
crc ^= m_poly;
crc >>= 1;
if (bit)
crc |= m_crchighbit;
}
m_crcinit_nondirect = crc;
}
}
unsigned long CRC::crctablefast(unsigned char* p, unsigned long len)
{
// fast lookup table algorithm without augmented zero bytes, e.g. used in pkzip.
// only usable with polynom orders of 8, 16, 24 or 32.
unsigned long crc = m_crcinit_direct;
if (m_refin)
crc = reflect(crc, m_order);
if (!m_refin)
while (len--)
crc = (crc << 8) ^ m_crctab[((crc >> (m_order - 8)) & 0xff) ^ *p++];
else
while (len--)
crc = (crc >> 8) ^ m_crctab[(crc & 0xff) ^ *p++];
if (m_refout ^ m_refin)
crc = reflect(crc, m_order);
crc ^= m_crcxor;
crc &= m_crcmask;
return (crc);
}
unsigned long CRC::crctable(unsigned char* p, unsigned long len)
{
// normal lookup table algorithm with augmented zero bytes.
// only usable with polynom orders of 8, 16, 24 or 32.
unsigned long crc = m_crcinit_nondirect;
if (m_refin)
crc = reflect(crc, m_order);
if (!m_refin)
while (len--)
crc = ((crc << 8) | *p++) ^ m_crctab[(crc >> (m_order - 8)) & 0xff];
else
while (len--)
crc = ((crc >> 8) | (*p++ << (m_order - 8))) ^ m_crctab[crc & 0xff];
if (!m_refin)
while (++len < m_order / 8)
crc = (crc << 8) ^ m_crctab[(crc >> (m_order - 8)) & 0xff];
else
while (++len < m_order / 8)
crc = (crc >> 8) ^ m_crctab[crc & 0xff];
if (m_refout ^ m_refin)
crc = reflect(crc, m_order);
crc ^= m_crcxor;
crc &= m_crcmask;
return (crc);
}
unsigned long CRC::crcbitbybit(unsigned char* p, unsigned long len)
{
// bit by bit algorithm with augmented zero bytes.
// does not use lookup table, suited for polynom orders between 1...32.
unsigned long i, j, c, bit;
unsigned long crc = m_crcinit_nondirect;
for (i = 0; i < len; i++)
{
c = (unsigned long) *p++;
if (m_refin)
c = reflect(c, 8);
for (j = 0x80; j; j >>= 1)
{
bit = crc & m_crchighbit;
crc <<= 1;
if (c & j)
crc |= 1;
if (bit)
crc ^= m_poly;
}
}
for (i = 0; i < m_order; i++)
{
bit = crc & m_crchighbit;
crc <<= 1;
if (bit)
crc ^= m_poly;
}
if (m_refout)
crc = reflect(crc, m_order);
crc ^= m_crcxor;
crc &= m_crcmask;
return (crc);
}
unsigned long CRC::crcbitbybitfast(unsigned char* p, unsigned long len)
{
// fast bit by bit algorithm without augmented zero bytes.
// does not use lookup table, suited for polynom orders between 1...32.
unsigned long i, j, c, bit;
unsigned long crc = m_crcinit_direct;
for (i = 0; i < len; i++)
{
c = (unsigned long) *p++;
if (m_refin)
c = reflect(c, 8);
for (j = 0x80; j; j >>= 1)
{
bit = crc & m_crchighbit;
crc <<= 1;
if (c & j)
bit ^= m_crchighbit;
if (bit)
crc ^= m_poly;
}
}
if (m_refout)
crc = reflect(crc, m_order);
crc ^= m_crcxor;
crc &= m_crcmask;
return (crc);
}
// ====================================================================
DStarCRC::DStarCRC() : crc(0)
{}
DStarCRC::~DStarCRC()
{}
void DStarCRC::fcsbit(unsigned char tbyte)
{
crc ^= tbyte;
if (crc & 1)
{
crc = (crc >> 1) ^ 0x8408; // X-modem CRC poly
}
else
{
crc = crc >> 1;
}
}
void DStarCRC::compute_crc(unsigned char *array, int size_buffer)
{
crc = 0xffff;
for (int n = 0; n < (size_buffer - 2); n++)
{
for (int m = 0; m < 8; m++)
{ //each bit must be calculated separately
fcsbit(bitRead(array[n], m));
}
}
crc ^= 0xffff;
}
bool DStarCRC::check_crc(unsigned char *array, int size_buffer)
{
compute_crc(array, size_buffer);
unsigned int crc_decoded = (array[size_buffer - 1] << 8) + array[size_buffer - 2]; //inversion msb lsb
if (crc_decoded == crc)
{
return true;
}
else
{
return false;
}
}
bool DStarCRC::check_crc(unsigned char *array, int size_buffer, unsigned int crcValue)
{
compute_crc(array, size_buffer+2); // size given is buffer size without CRC
if (crcValue == crc)
{
return true;
}
else
{
return false;
}
}
} // namespace DSDcc
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