57 lines
1.4 KiB
C
57 lines
1.4 KiB
C
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/* crc32.c -- compute the CRC-32 of a data stream
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* Copyright (C) 1995 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/* $Id$ */
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#define __CRC32_C /* identifies this source module */
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#include "zip.h"
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#ifndef USE_ZLIB
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#ifndef ASM_CRC
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#ifndef ZCONST
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# define ZCONST const
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#endif
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#ifdef CRC32
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# undef CRC32
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#endif
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#define CRC32(c, b) (crc_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8))
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#define DO1(buf) crc = CRC32(crc, *buf++)
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#define DO2(buf) DO1(buf); DO1(buf)
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#define DO4(buf) DO2(buf); DO2(buf)
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#define DO8(buf) DO4(buf); DO4(buf)
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/* ========================================================================= */
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ulg crc32(crc, buf, len)
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register ulg crc; /* crc shift register */
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register ZCONST uch *buf; /* pointer to bytes to pump through */
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extent len; /* number of bytes in buf[] */
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/* Run a set of bytes through the crc shift register. If buf is a NULL
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pointer, then initialize the crc shift register contents instead.
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Return the current crc in either case. */
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{
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register ZCONST ulg near *crc_table;
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if (buf == NULL) return 0L;
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crc_table = get_crc_table();
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crc = crc ^ 0xffffffffL;
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#ifndef NO_UNROLLED_LOOPS
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while (len >= 8) {
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DO8(buf);
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len -= 8;
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}
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#endif
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if (len) do {
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DO1(buf);
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} while (--len);
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return crc ^ 0xffffffffL; /* (instead of ~c for 64-bit machines) */
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}
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#endif /* !ASM_CRC */
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#endif /* !USE_ZLIB */
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