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 * The original JFFS, from which the design for JFFS2 was derived,
9 * was designed and implemented by Axis Communications AB.
10 *
11 * The contents of this file are subject to the Red Hat eCos Public
12 * License Version 1.1 (the "Licence"); you may not use this file
13 * except in compliance with the Licence. You may obtain a copy of
14 * the Licence at http://www.redhat.com/
15 *
16 * Software distributed under the Licence is distributed on an "AS IS"
17 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.
18 * See the Licence for the specific language governing rights and
19 * limitations under the Licence.
20 *
21 * The Original Code is JFFS2 - Journalling Flash File System, version 2
22 *
23 * Alternatively, the contents of this file may be used under the
24 * terms of the GNU General Public License version 2 (the "GPL"), in
25 * which case the provisions of the GPL are applicable instead of the
26 * above. If you wish to allow the use of your version of this file
27 * only under the terms of the GPL and not to allow others to use your
28 * version of this file under the RHEPL, indicate your decision by
29 * deleting the provisions above and replace them with the notice and
30 * other provisions required by the GPL. If you do not delete the
31 * provisions above, a recipient may use your version of this file
32 * under either the RHEPL or the GPL.
33 *
34 * $Id: compr_rtime.c,v 1.2 2002/01/24 22:58:42 rfeany Exp $
35 *
36 *
37 * Very simple lz77-ish encoder.
38 *
39 * Theory of operation: Both encoder and decoder have a list of "last
40 * occurances" for every possible source-value; after sending the
41 * first source-byte, the second byte indicated the "run" length of
42 * matches
43 *
44 * The algorithm is intended to only send "whole bytes", no bit-messing.
45 *
46 */
47
48 #include <config.h>
49 #include <jffs2/jffs2.h>
50
rtime_decompress(unsigned char * data_in,unsigned char * cpage_out,u32 srclen,u32 destlen)51 void rtime_decompress(unsigned char *data_in, unsigned char *cpage_out,
52 u32 srclen, u32 destlen)
53 {
54 int positions[256];
55 int outpos;
56 int pos;
57 int i;
58
59 outpos = pos = 0;
60
61 for (i = 0; i < 256; positions[i++] = 0);
62
63 while (outpos<destlen) {
64 unsigned char value;
65 int backoffs;
66 int repeat;
67
68 value = data_in[pos++];
69 cpage_out[outpos++] = value; /* first the verbatim copied byte */
70 repeat = data_in[pos++];
71 backoffs = positions[value];
72
73 positions[value]=outpos;
74 if (repeat) {
75 if (backoffs + repeat >= outpos) {
76 while(repeat) {
77 cpage_out[outpos++] = cpage_out[backoffs++];
78 repeat--;
79 }
80 } else {
81 for (i = 0; i < repeat; i++)
82 *(cpage_out + outpos + i) = *(cpage_out + backoffs + i);
83 outpos+=repeat;
84 }
85 }
86 }
87 }
88