| | 1 | /* crc32.c -- compute the CRC-32 of a data stream |
| | 2 | * Copyright (C) 1995 Mark Adler |
| | 3 | * For conditions of distribution and use, see copyright notice in zlib.h |
| | 4 | */ |
| | 5 | |
| | 6 | /* $Id$ */ |
| | 7 | |
| | 8 | #define __CRC32_C /* identifies this source module */ |
| | 9 | |
| | 10 | #include "zip.h" |
| | 11 | |
| | 12 | #ifndef USE_ZLIB |
| | 13 | #ifndef ASM_CRC |
| | 14 | |
| | 15 | #ifndef ZCONST |
| | 16 | # define ZCONST const |
| | 17 | #endif |
| | 18 | |
| | 19 | #ifdef CRC32 |
| | 20 | # undef CRC32 |
| | 21 | #endif |
| | 22 | #define CRC32(c, b) (crc_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8)) |
| | 23 | #define DO1(buf) crc = CRC32(crc, *buf++) |
| | 24 | #define DO2(buf) DO1(buf); DO1(buf) |
| | 25 | #define DO4(buf) DO2(buf); DO2(buf) |
| | 26 | #define DO8(buf) DO4(buf); DO4(buf) |
| | 27 | |
| | 28 | /* ========================================================================= */ |
| | 29 | ulg crc32(crc, buf, len) |
| | 30 | register ulg crc; /* crc shift register */ |
| | 31 | register ZCONST uch *buf; /* pointer to bytes to pump through */ |
| | 32 | extent len; /* number of bytes in buf[] */ |
| | 33 | /* Run a set of bytes through the crc shift register. If buf is a NULL |
| | 34 | pointer, then initialize the crc shift register contents instead. |
| | 35 | Return the current crc in either case. */ |
| | 36 | { |
| | 37 | register ZCONST ulg near *crc_table; |
| | 38 | |
| | 39 | if (buf == NULL) return 0L; |
| | 40 | |
| | 41 | crc_table = get_crc_table(); |
| | 42 | |
| | 43 | crc = crc ^ 0xffffffffL; |
| | 44 | #ifndef NO_UNROLLED_LOOPS |
| | 45 | while (len >= 8) { |
| | 46 | DO8(buf); |
| | 47 | len -= 8; |
| | 48 | } |
| | 49 | #endif |
| | 50 | if (len) do { |
| | 51 | DO1(buf); |
| | 52 | } while (--len); |
| | 53 | return crc ^ 0xffffffffL; /* (instead of ~c for 64-bit machines) */ |
| | 54 | } |
| | 55 | #endif /* !ASM_CRC */ |
| | 56 | #endif /* !USE_ZLIB */ |
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