src/bin/unzip/crc32.c

   1 /*
   2   Copyright (c) 1990-2000 Info-ZIP.  All rights reserved.
   3
   4   See the accompanying file LICENSE, version 2000-Apr-09 or later
   5   (the contents of which are also included in zip.h) for terms of use.
   6   If, for some reason, all these files are missing, the Info-ZIP license
   7   also may be found at:  ftp://ftp.info-zip.org/pub/infozip/license.html
   8 */
   9 /* crc32.c -- compute the CRC-32 of a data stream
  10  * Copyright (C) 1995 Mark Adler
  11  * For conditions of distribution and use, see copyright notice in zlib.h
  12  */
  13
  14 /* $Id: crc32.c 1101 2002-09-21 14:54:45Z darkwyrm $ */
  15
  16 #define __CRC32_C       /* identifies this source module */
  17
  18 #include "zip.h"
  19
  20 #ifndef USE_ZLIB
  21 #ifndef ASM_CRC
  22
  23 #ifndef ZCONST
  24 #  define ZCONST const
  25 #endif
  26
  27 #ifdef CRC32
  28 #  undef CRC32
  29 #endif
  30 #define CRC32(c, b) (crc_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8))
  31 #define DO1(buf)  crc = CRC32(crc, *buf++)
  32 #define DO2(buf)  DO1(buf); DO1(buf)
  33 #define DO4(buf)  DO2(buf); DO2(buf)
  34 #define DO8(buf)  DO4(buf); DO4(buf)
  35
  36 /* ========================================================================= */
  37 ulg crc32(crc, buf, len)
  38     register ulg crc;           /* crc shift register */
  39     register ZCONST uch *buf;   /* pointer to bytes to pump through */
  40     extent len;                 /* number of bytes in buf[] */
  41 /* Run a set of bytes through the crc shift register.  If buf is a NULL
  42    pointer, then initialize the crc shift register contents instead.
  43    Return the current crc in either case. */
  44 {
  45   register ZCONST ulg near *crc_table;
  46
  47   if (buf == NULL) return 0L;
  48
  49   crc_table = get_crc_table();
  50
  51   crc = crc ^ 0xffffffffL;
  52 #ifndef NO_UNROLLED_LOOPS
  53   while (len >= 8) {
  54     DO8(buf);
  55     len -= 8;
  56   }
  57 #endif
  58   if (len) do {
  59     DO1(buf);
  60   } while (--len);
  61   return crc ^ 0xffffffffL;     /* (instead of ~c for 64-bit machines) */
  62 }
  63 #endif /* !ASM_CRC */
  64 #endif /* !USE_ZLIB */