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EnigmA Amiga Run 1997 April
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EnigmA AMIGA RUN 17 (1997)(G.R. Edizioni)(IT)[!][issue 1997-04][EAR-CD].iso
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CRC32.c
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1995-11-02
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/*
** $VER: CRC32.c (16.4.94) by Flavio Stanchina
** Adapted from comp.compression FAQ
**
** Changed to do one-byte-at-a-time CRC
** Don't complement CRC for simplicity
*/
#include <exec/types.h>
#include "CRC32.h"
ULONG crc32_table[256];
/*
** Build auxiliary table for parallel byte-at-a-time CRC-32.
*/
VOID CRC32_init(VOID)
{
ULONG c, i, j;
for(i = 0; i < 256; ++i)
{
for(c = i << 24, j = 8; j > 0; --j)
c = c & 0x80000000 ? (c << 1) ^ CRC32_POLY : (c << 1);
crc32_table[i] = c;
}
}
ULONG CRC32_stream(UBYTE c, ULONG crc)
{
return (crc << 8) ^ crc32_table[(crc >> 24) ^ c];
}
ULONG CRC32_block(UBYTE *buf, ULONG len)
{
ULONG crc = CRC32_INITIAL;
UBYTE *p;
for(p = buf; len > 0; ++p, --len)
crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *p];
return crc; /* to simplify some things */
}
ULONG CRC32_blocks(UBYTE *buf, ULONG len, ULONG crc)
{
UBYTE *p;
for(p = buf; len > 0; ++p, --len)
crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *p];
return crc; /* to simplify some things */
}