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41 lines
604 B
C
41 lines
604 B
C
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#include <u.h>
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#include <libc.h>
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#include <flate.h>
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ulong*
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mkcrctab(ulong poly)
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{
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ulong *crctab;
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ulong crc;
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int i, j;
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crctab = malloc(256 * sizeof(ulong));
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if(crctab == nil)
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return nil;
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for(i = 0; i < 256; i++){
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crc = i;
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for(j = 0; j < 8; j++){
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if(crc & 1)
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crc = (crc >> 1) ^ poly;
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else
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crc >>= 1;
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}
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crctab[i] = crc;
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}
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return crctab;
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}
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ulong
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blockcrc(ulong *crctab, ulong crc, void *vbuf, int n)
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{
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uchar *buf, *ebuf;
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crc ^= 0xffffffff;
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buf = vbuf;
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ebuf = buf + n;
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while(buf < ebuf)
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crc = crctab[(crc & 0xff) ^ *buf++] ^ (crc >> 8);
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return crc ^ 0xffffffff;
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}
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