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/*
* Copyright (c) 2008 Johan Christiansen
* Copyright (c) 2012 Jeppe Ledet-Pedersen <jlp@satlab.org>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <stdio.h>
#include <string.h>
void ccsds_generate_sequence(char* sequence, int length)
{
char x[9] = { 1, 1, 1, 1, 1, 1, 1, 1, 1 };
int i;
/* Generate the sequence */
memset(sequence, 0, length);
/* The pseudo random sequence shall be generated using the polynomial
* h(x) = x8 + x7 + x5 + x3 + 1 */
for (i = 0; i < length * 8; i++) {
sequence[i / 8] = sequence[i / 8] | x[1] << 7 >> (i % 8);
x[0] = (x[8] + x[6] + x[4] + x[1]) % 2;
x[1] = x[2];
x[2] = x[3];
x[3] = x[4];
x[4] = x[5];
x[5] = x[6];
x[6] = x[7];
x[7] = x[8];
x[8] = x[0];
}
}
void ccsds_xor_sequence(unsigned char* data, char* sequence, int length)
{
int i;
for (i = 0; i < length; i++)
data[i] ^= sequence[i];
}
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