| 1 | /* crc32.c -- compute the CRC-32 of a data stream
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| 2 | * Copyright (C) 1995-2005 Mark Adler
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| 3 | * For conditions of distribution and use, see copyright notice in zlib.h
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| 4 | *
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| 5 | * Thanks to Rodney Brown <[email protected]> for his contribution of faster
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| 6 | * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
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| 7 | * tables for updating the shift register in one step with three exclusive-ors
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| 8 | * instead of four steps with four exclusive-ors. This results in about a
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| 9 | * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
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| 10 | */
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| 11 |
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| 12 | /* @(#) $Id$ */
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| 13 |
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| 14 | /*
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| 15 | Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
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| 16 | protection on the static variables used to control the first-use generation
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| 17 | of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should
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| 18 | first call get_crc_table() to initialize the tables before allowing more than
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| 19 | one thread to use crc32().
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| 20 | */
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| 21 |
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| 22 | #ifdef MAKECRCH
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| 23 | # include <stdio.h>
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| 24 | # ifndef DYNAMIC_CRC_TABLE
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| 25 | # define DYNAMIC_CRC_TABLE
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| 26 | # endif /* !DYNAMIC_CRC_TABLE */
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| 27 | #endif /* MAKECRCH */
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| 28 |
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| 29 | #include "zutil.h" /* for STDC and FAR definitions */
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| 30 |
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| 31 | #define local static
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| 32 |
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| 33 | /* Find a four-byte integer type for crc32_little() and crc32_big(). */
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| 34 | #ifndef NOBYFOUR
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| 35 | # ifdef STDC /* need ANSI C limits.h to determine sizes */
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| 36 | # include <limits.h>
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| 37 | # define BYFOUR
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| 38 | # if (UINT_MAX == 0xffffffffUL)
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| 39 | typedef unsigned int u4;
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| 40 | # else
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| 41 | # if (ULONG_MAX == 0xffffffffUL)
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