SSB_HighSpeed_Modem/hsmodem/crc16.cpp
Kurt Moraw caff38495d update
2020-11-05 19:11:57 +01:00

84 lines
2.3 KiB
C++
Executable File

/*
* High Speed modem to transfer data in a 2,7kHz SSB channel
* =========================================================
* Author: DJ0ABR
*
* (c) DJ0ABR
* www.dj0abr.de
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
#include "hsmodem.h"
// since we use a static crc register we need TWO separated registers
// for RX and TX to get it thread safe, no.2 is for file ID generation
uint16_t reg16[3] = {0xffff,0xffff}; // shift register
uint16_t Crc16_bytecalc(int rxtx, uint8_t byt)
{
uint16_t polynom = 0x8408; // generator polynom
for (int i = 0; i < 8; ++i)
{
if ((reg16[rxtx] & 1) != (byt & 1))
reg16[rxtx] = (uint16_t)((reg16[rxtx] >> 1) ^ polynom);
else
reg16[rxtx] >>= 1;
byt >>= 1;
}
return reg16[rxtx];
}
uint16_t Crc16_messagecalc(int rxtx, uint8_t *data,int len)
{
reg16[rxtx] = 0xffff;
for (int i = 0; i < len; i++)
reg16[rxtx] = Crc16_bytecalc(rxtx,data[i]);
return reg16[rxtx];
}
// =================================================================
uint32_t reg32[2] = {0xffffffff,0xffffffff}; // Shiftregister
void crc32_bytecalc(int rxtx, unsigned char byte)
{
int i;
uint32_t polynom = 0xEDB88320; // Generatorpolynom
for (i=0; i<8; ++i)
{
if ((reg32[rxtx]&1) != (byte&1))
reg32[rxtx] = (reg32[rxtx]>>1)^polynom;
else
reg32[rxtx] >>= 1;
byte >>= 1;
}
}
uint32_t crc32_messagecalc(int rxtx, unsigned char *data, int len)
{
int i;
reg32[rxtx] = 0xffffffff;
for(i=0; i<len; i++) {
crc32_bytecalc(rxtx,data[i]);
}
return reg32[rxtx] ^ 0xffffffff;
}