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1 /*
2  * JFFS2 -- Journalling Flash File System, Version 2.
3  *
4  * Copyright (C) 2001 Red Hat, Inc.
5  *
6  * Created by Arjan van de Ven <arjanv@redhat.com>
7  *
8  * Heavily modified by Russ Dill <Russ.Dill@asu.edu> in an attempt at
9  * a little more speed.
10  *
11  * The original JFFS, from which the design for JFFS2 was derived,
12  * was designed and implemented by Axis Communications AB.
13  *
14  * The contents of this file are subject to the Red Hat eCos Public
15  * License Version 1.1 (the "Licence"); you may not use this file
16  * except in compliance with the Licence.  You may obtain a copy of
17  * the Licence at http://www.redhat.com/
18  *
19  * Software distributed under the Licence is distributed on an "AS IS"
20  * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.
21  * See the Licence for the specific language governing rights and
22  * limitations under the Licence.
23  *
24  * The Original Code is JFFS2 - Journalling Flash File System, version 2
25  *
26  * Alternatively, the contents of this file may be used under the
27  * terms of the GNU General Public License version 2 (the "GPL"), in
28  * which case the provisions of the GPL are applicable instead of the
29  * above.  If you wish to allow the use of your version of this file
30  * only under the terms of the GPL and not to allow others to use your
31  * version of this file under the RHEPL, indicate your decision by
32  * deleting the provisions above and replace them with the notice and
33  * other provisions required by the GPL.  If you do not delete the
34  * provisions above, a recipient may use your version of this file
35  * under either the RHEPL or the GPL.
36  *
37  * $Id: compr_rubin.c,v 1.2 2002/01/24 22:58:42 rfeany Exp $
38  *
39  */
40 
41 #include <config.h>
42 #include <jffs2/jffs2.h>
43 #include <jffs2/compr_rubin.h>
44 
45 
rubin_do_decompress(unsigned char * bits,unsigned char * in,unsigned char * page_out,__u32 destlen)46 void rubin_do_decompress(unsigned char *bits, unsigned char *in,
47 			 unsigned char *page_out, __u32 destlen)
48 {
49 	register char *curr = (char *)page_out;
50 	char *end = (char *)(page_out + destlen);
51 	register unsigned long temp;
52 	register unsigned long result;
53 	register unsigned long p;
54 	register unsigned long q;
55 	register unsigned long rec_q;
56 	register unsigned long bit;
57 	register long i0;
58 	unsigned long i;
59 
60 	/* init_pushpull */
61 	temp = *(u32 *) in;
62 	bit = 16;
63 
64 	/* init_rubin */
65 	q = 0;
66 	p = (long) (2 * UPPER_BIT_RUBIN);
67 
68 	/* init_decode */
69 	rec_q = (in[0] << 8) | in[1];
70 
71 	while (curr < end) {
72 		/* in byte */
73 
74 		result = 0;
75 		for (i = 0; i < 8; i++) {
76 			/* decode */
77 
78 			while ((q & UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN)) {
79 				q &= ~UPPER_BIT_RUBIN;
80 				q <<= 1;
81 				p <<= 1;
82 				rec_q &= ~UPPER_BIT_RUBIN;
83 				rec_q <<= 1;
84 				rec_q |= (temp >> (bit++ ^ 7)) & 1;
85 				if (bit > 31) {
86 					u32 *p = (u32 *)in;
87 					bit = 0;
88 					temp = *(++p);
89 					in = (unsigned char *)p;
90 				}
91 			}
92 			i0 =  (bits[i] * p) >> 8;
93 
94 			if (i0 <= 0) i0 = 1;
95 			/* if it fails, it fails, we have our crc
96 			if (i0 >= p) i0 = p - 1; */
97 
98 			result >>= 1;
99 			if (rec_q < q + i0) {
100 				/* result |= 0x00; */
101 				p = i0;
102 			} else {
103 				result |= 0x80;
104 				p -= i0;
105 				q += i0;
106 			}
107 		}
108 		*(curr++) = result;
109 	}
110 }
111 
dynrubin_decompress(unsigned char * data_in,unsigned char * cpage_out,unsigned long sourcelen,unsigned long dstlen)112 void dynrubin_decompress(unsigned char *data_in, unsigned char *cpage_out,
113 		   unsigned long sourcelen, unsigned long dstlen)
114 {
115 	unsigned char bits[8];
116 	int c;
117 
118 	for (c=0; c<8; c++)
119 		bits[c] = (256 - data_in[c]);
120 
121 	rubin_do_decompress(bits, data_in+8, cpage_out, dstlen);
122 }
123