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#include "boot.h"
/*
* from Rob Warnock
*/
static ulong crc32tab[256]; /* initialised on first call to crc32 */
enum {
CRC32POLY = 0x04c11db7 /* AUTODIN II, Ethernet, & FDDI */
};
/*
* Build auxiliary table for parallel byte-at-a-time CRC-32.
*/
static void
initcrc32(void)
{
int i, j;
ulong c;
for(i = 0; i < 256; i++) {
for(c = i << 24, j = 8; j > 0; j--)
if(c & (1<<31))
c = (c<<1) ^ CRC32POLY;
else
c <<= 1;
crc32tab[i] = c;
}
}
ulong
crc32(void *buf, int n, ulong crc)
{
uchar *p;
if(crc32tab[1] == 0)
initcrc32();
crc = ~crc;
for(p = buf; --n >= 0;)
crc = (crc << 8) ^ crc32tab[(crc >> 24) ^ *p++];
return ~crc;
}
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