xref: /freebsd/contrib/libarchive/libarchive/archive_crc32.h (revision caf54c4f6ce7f1612a528170c1aa3c3fe4f8b153)
1*caf54c4fSMartin Matuska /*-
2*caf54c4fSMartin Matuska  * Copyright (c) 2009 Joerg  Sonnenberger
3*caf54c4fSMartin Matuska  * All rights reserved.
4*caf54c4fSMartin Matuska  *
5*caf54c4fSMartin Matuska  * Redistribution and use in source and binary forms, with or without
6*caf54c4fSMartin Matuska  * modification, are permitted provided that the following conditions
7*caf54c4fSMartin Matuska  * are met:
8*caf54c4fSMartin Matuska  * 1. Redistributions of source code must retain the above copyright
9*caf54c4fSMartin Matuska  *    notice, this list of conditions and the following disclaimer.
10*caf54c4fSMartin Matuska  * 2. Redistributions in binary form must reproduce the above copyright
11*caf54c4fSMartin Matuska  *    notice, this list of conditions and the following disclaimer in the
12*caf54c4fSMartin Matuska  *    documentation and/or other materials provided with the distribution.
13*caf54c4fSMartin Matuska  *
14*caf54c4fSMartin Matuska  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
15*caf54c4fSMartin Matuska  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16*caf54c4fSMartin Matuska  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17*caf54c4fSMartin Matuska  * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
18*caf54c4fSMartin Matuska  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19*caf54c4fSMartin Matuska  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20*caf54c4fSMartin Matuska  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21*caf54c4fSMartin Matuska  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22*caf54c4fSMartin Matuska  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23*caf54c4fSMartin Matuska  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24*caf54c4fSMartin Matuska  *
25*caf54c4fSMartin Matuska  * $FreeBSD: head/lib/libarchive/archive_crc32.h 201102 2009-12-28 03:11:36Z kientzle $
26*caf54c4fSMartin Matuska  */
27*caf54c4fSMartin Matuska 
28*caf54c4fSMartin Matuska #ifndef __LIBARCHIVE_BUILD
29*caf54c4fSMartin Matuska #error This header is only to be used internally to libarchive.
30*caf54c4fSMartin Matuska #endif
31*caf54c4fSMartin Matuska 
32*caf54c4fSMartin Matuska /*
33*caf54c4fSMartin Matuska  * When zlib is unavailable, we should still be able to validate
34*caf54c4fSMartin Matuska  * uncompressed zip archives.  That requires us to be able to compute
35*caf54c4fSMartin Matuska  * the CRC32 check value.  This is a drop-in compatible replacement
36*caf54c4fSMartin Matuska  * for crc32() from zlib.  It's slower than the zlib implementation,
37*caf54c4fSMartin Matuska  * but still pretty fast: This runs about 300MB/s on my 3GHz P4
38*caf54c4fSMartin Matuska  * compared to about 800MB/s for the zlib implementation.
39*caf54c4fSMartin Matuska  */
40*caf54c4fSMartin Matuska static unsigned long
41*caf54c4fSMartin Matuska crc32(unsigned long crc, const void *_p, size_t len)
42*caf54c4fSMartin Matuska {
43*caf54c4fSMartin Matuska 	unsigned long crc2, b, i;
44*caf54c4fSMartin Matuska 	const unsigned char *p = _p;
45*caf54c4fSMartin Matuska 	static volatile int crc_tbl_inited = 0;
46*caf54c4fSMartin Matuska 	static unsigned long crc_tbl[256];
47*caf54c4fSMartin Matuska 
48*caf54c4fSMartin Matuska 	if (!crc_tbl_inited) {
49*caf54c4fSMartin Matuska 		for (b = 0; b < 256; ++b) {
50*caf54c4fSMartin Matuska 			crc2 = b;
51*caf54c4fSMartin Matuska 			for (i = 8; i > 0; --i) {
52*caf54c4fSMartin Matuska 				if (crc2 & 1)
53*caf54c4fSMartin Matuska 					crc2 = (crc2 >> 1) ^ 0xedb88320UL;
54*caf54c4fSMartin Matuska 				else
55*caf54c4fSMartin Matuska 					crc2 = (crc2 >> 1);
56*caf54c4fSMartin Matuska 			}
57*caf54c4fSMartin Matuska 			crc_tbl[b] = crc2;
58*caf54c4fSMartin Matuska 		}
59*caf54c4fSMartin Matuska 		crc_tbl_inited = 1;
60*caf54c4fSMartin Matuska 	}
61*caf54c4fSMartin Matuska 
62*caf54c4fSMartin Matuska 	crc = crc ^ 0xffffffffUL;
63*caf54c4fSMartin Matuska 	while (len--)
64*caf54c4fSMartin Matuska 		crc = crc_tbl[(crc ^ *p++) & 0xff] ^ (crc >> 8);
65*caf54c4fSMartin Matuska 	return (crc ^ 0xffffffffUL);
66*caf54c4fSMartin Matuska }
67