1 /*
2 * uzlib - tiny deflate/inflate library (deflate, gzip, zlib)
3 *
4 * Copyright (c) 2003 by Joergen Ibsen / Jibz
5 * All Rights Reserved
6 *
7 * http://www.ibsensoftware.com/
8 *
9 * Copyright (c) 2014-2018 by Paul Sokolovsky
10 *
11 * This software is provided 'as-is', without any express
12 * or implied warranty. In no event will the authors be
13 * held liable for any damages arising from the use of
14 * this software.
15 *
16 * Permission is granted to anyone to use this software
17 * for any purpose, including commercial applications,
18 * and to alter it and redistribute it freely, subject to
19 * the following restrictions:
20 *
21 * 1. The origin of this software must not be
22 * misrepresented; you must not claim that you
23 * wrote the original software. If you use this
24 * software in a product, an acknowledgment in
25 * the product documentation would be appreciated
26 * but is not required.
27 *
28 * 2. Altered source versions must be plainly marked
29 * as such, and must not be misrepresented as
30 * being the original software.
31 *
32 * 3. This notice may not be removed or altered from
33 * any source distribution.
34 */
35
36 #include "tinf.h"
37
uzlib_zlib_parse_header(TINF_DATA * d)38 int uzlib_zlib_parse_header(TINF_DATA *d)
39 {
40 unsigned char cmf, flg;
41
42 /* -- get header bytes -- */
43
44 cmf = uzlib_get_byte(d);
45 flg = uzlib_get_byte(d);
46
47 /* -- check format -- */
48
49 /* check checksum */
50 if ((256*cmf + flg) % 31) return TINF_DATA_ERROR;
51
52 /* check method is deflate */
53 if ((cmf & 0x0f) != 8) return TINF_DATA_ERROR;
54
55 /* check window size is valid */
56 if ((cmf >> 4) > 7) return TINF_DATA_ERROR;
57
58 /* check there is no preset dictionary */
59 if (flg & 0x20) return TINF_DATA_ERROR;
60
61 /* initialize for adler32 checksum */
62 d->checksum_type = TINF_CHKSUM_ADLER;
63 d->checksum = 1;
64
65 return cmf >> 4;
66 }
67