1 /*
2 * CRC32 checksum
3 *
4 * Copyright (c) 1998-2003 by Joergen Ibsen / Jibz
5 * All Rights Reserved
6 *
7 * http://www.ibsensoftware.com/
8 *
9 * This software is provided 'as-is', without any express
10 * or implied warranty. In no event will the authors be
11 * held liable for any damages arising from the use of
12 * this software.
13 *
14 * Permission is granted to anyone to use this software
15 * for any purpose, including commercial applications,
16 * and to alter it and redistribute it freely, subject to
17 * the following restrictions:
18 *
19 * 1. The origin of this software must not be
20 * misrepresented; you must not claim that you
21 * wrote the original software. If you use this
22 * software in a product, an acknowledgment in
23 * the product documentation would be appreciated
24 * but is not required.
25 *
26 * 2. Altered source versions must be plainly marked
27 * as such, and must not be misrepresented as
28 * being the original software.
29 *
30 * 3. This notice may not be removed or altered from
31 * any source distribution.
32 */
33
34 /*
35 * CRC32 algorithm taken from the zlib source, which is
36 * Copyright (C) 1995-1998 Jean-loup Gailly and Mark Adler
37 */
38
39 #include "tinf.h"
40
41 static const unsigned int tinf_crc32tab[16] = {
42 0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac, 0x76dc4190,
43 0x6b6b51f4, 0x4db26158, 0x5005713c, 0xedb88320, 0xf00f9344,
44 0xd6d6a3e8, 0xcb61b38c, 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278,
45 0xbdbdf21c
46 };
47
48 /* crc is previous value for incremental computation, 0xffffffff initially */
uzlib_crc32(const void * data,unsigned int length,uint32_t crc)49 uint32_t uzlib_crc32(const void *data, unsigned int length, uint32_t crc)
50 {
51 const unsigned char *buf = (const unsigned char *)data;
52 unsigned int i;
53
54 for (i = 0; i < length; ++i)
55 {
56 crc ^= buf[i];
57 crc = tinf_crc32tab[crc & 0x0f] ^ (crc >> 4);
58 crc = tinf_crc32tab[crc & 0x0f] ^ (crc >> 4);
59 }
60
61 // return value suitable for passing in next time, for final value invert it
62 return crc/* ^ 0xffffffff*/;
63 }
64