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/* tnt: Hostmode Terminal for TNC
Copyright (C) 1993 by Mark Wahl
For license details see documentation
Procedures for autobin-checksum (crc.c)
created: Mark Wahl DL4YBG 94/01/17
updated: Mark Wahl DL4YBG 94/01/17
*/
static int crcbit[8] = {
0x9188,0x48c4,0x2462,0x1231,0x8108,0x4084,0x2042,0x1021
};
static int bittab[8] = { 128,64,32,16,8,4,2,1 };
static int crctab[256];
void init_crc(void)
{
int i,j;
for (i = 0; i < 256; i++) {
crctab[i] = 0;
for (j = 0; j < 8; j++) {
if ((bittab[j] & i) != 0) {
crctab[i] = crctab[i] ^ crcbit[j];
}
}
}
}
/* calculate checksum for autobin-protocol */
unsigned int calc_crc(unsigned char* buf, int n, unsigned crc)
{
while (--n >= 0)
crc = (crctab[(crc >> 8)] ^ ((crc << 8) | *buf++)) & 0xffff;
return crc;
}
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