kopia lustrzana https://github.com/xdsopl/qsstv
96 wiersze
4.3 KiB
C++
96 wiersze
4.3 KiB
C++
/******************************************************************************/
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/* */
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/* University of Kaiserslautern, Institute of Communications Engineering */
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/* Copyright (C) 2004 Torsten Schorr */
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/* */
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/* Author(s) : Torsten Schorr (schorr@eit.uni-kl.de) */
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/* Project start: 23.07.2004 */
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/* Last change : 23.07.2004 */
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/* */
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/******************************************************************************/
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/* */
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/* This program is free software; you can redistribute it and/or modify */
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/* it under the terms of the GNU General Public License as published by */
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/* the Free Software Foundation; either version 2 of the License, or */
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/* (at your option) any later version. */
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/* */
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/* This program is distributed in the hope that it will be useful, */
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/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
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/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
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/* GNU General Public License for more details. */
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/* */
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/* You should have received a copy of the GNU General Public License */
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/* along with this program; if not, write to the Free Software */
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/* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/* */
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/******************************************************************************/
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/******************************************************************************/
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/* */
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/* crc16_bytewise.c */
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/* */
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/******************************************************************************/
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/* Description: */
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/* CRC-16 checksum calculation of a byte stream */
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/* Usage: */
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/* */
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/* crc16_bytewise(double *checksum, unsigned char *in, long N); */
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/* */
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/* calculates double checksum of uint8 bytes */
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/* */
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/******************************************************************************/
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/*************
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*
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* adjusted for use in own plain C programa
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* by M.Bos - PA0MBO
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*
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* Date Dec 9th 2007
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*/
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#include <math.h>
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#include <stdlib.h>
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/******************************************************************************/
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/* function */
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/******************************************************************************/
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void crc16_bytewise(double /*@out@ */ checksum[],unsigned char in[], long N)
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{
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long int i;
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int j;
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unsigned int b = 0xFFFF;
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unsigned int x = 0x1021; /* (1) 0001000000100001 */
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unsigned int y;
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for (i = 0; i < N - 2; i++)
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{
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for (j = 7; j >= 0; j--)
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{
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y = (((b >> 15) + (unsigned int) (in[i] >> j)) & 0x01) & 0x01; /* extra parenth pa0mbo */
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if (y == 1)
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b = ((b << 1) ^ x);
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else
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b = (b << 1);
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}
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}
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for (i = N - 2; i < N; i++)
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{
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for (j = 7; j >= 0; j--)
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{
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y = (((b >> 15) + (unsigned int) ((in[i] >> j) & 0x01)) ^ 0x01) & 0x01; /* extra parent pa0mbo */
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if (y == 1)
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b = ((b << 1) ^ x);
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else
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b = (b << 1);
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}
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}
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*checksum = (double) (b & 0xFFFF);
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}
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