1*4882a593Smuzhiyun /*
2*4882a593Smuzhiyun * JFFS2 -- Journalling Flash File System, Version 2.
3*4882a593Smuzhiyun *
4*4882a593Smuzhiyun * Copyright (C) 2001 Red Hat, Inc.
5*4882a593Smuzhiyun *
6*4882a593Smuzhiyun * Created by Arjan van de Ven <arjanv@redhat.com>
7*4882a593Smuzhiyun *
8*4882a593Smuzhiyun * The original JFFS, from which the design for JFFS2 was derived,
9*4882a593Smuzhiyun * was designed and implemented by Axis Communications AB.
10*4882a593Smuzhiyun *
11*4882a593Smuzhiyun * The contents of this file are subject to the Red Hat eCos Public
12*4882a593Smuzhiyun * License Version 1.1 (the "Licence"); you may not use this file
13*4882a593Smuzhiyun * except in compliance with the Licence. You may obtain a copy of
14*4882a593Smuzhiyun * the Licence at http://www.redhat.com/
15*4882a593Smuzhiyun *
16*4882a593Smuzhiyun * Software distributed under the Licence is distributed on an "AS IS"
17*4882a593Smuzhiyun * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.
18*4882a593Smuzhiyun * See the Licence for the specific language governing rights and
19*4882a593Smuzhiyun * limitations under the Licence.
20*4882a593Smuzhiyun *
21*4882a593Smuzhiyun * The Original Code is JFFS2 - Journalling Flash File System, version 2
22*4882a593Smuzhiyun *
23*4882a593Smuzhiyun * Alternatively, the contents of this file may be used under the
24*4882a593Smuzhiyun * terms of the GNU General Public License version 2 (the "GPL"), in
25*4882a593Smuzhiyun * which case the provisions of the GPL are applicable instead of the
26*4882a593Smuzhiyun * above. If you wish to allow the use of your version of this file
27*4882a593Smuzhiyun * only under the terms of the GPL and not to allow others to use your
28*4882a593Smuzhiyun * version of this file under the RHEPL, indicate your decision by
29*4882a593Smuzhiyun * deleting the provisions above and replace them with the notice and
30*4882a593Smuzhiyun * other provisions required by the GPL. If you do not delete the
31*4882a593Smuzhiyun * provisions above, a recipient may use your version of this file
32*4882a593Smuzhiyun * under either the RHEPL or the GPL.
33*4882a593Smuzhiyun *
34*4882a593Smuzhiyun * $Id: compr_rtime.c,v 1.2 2002/01/24 22:58:42 rfeany Exp $
35*4882a593Smuzhiyun *
36*4882a593Smuzhiyun *
37*4882a593Smuzhiyun * Very simple lz77-ish encoder.
38*4882a593Smuzhiyun *
39*4882a593Smuzhiyun * Theory of operation: Both encoder and decoder have a list of "last
40*4882a593Smuzhiyun * occurances" for every possible source-value; after sending the
41*4882a593Smuzhiyun * first source-byte, the second byte indicated the "run" length of
42*4882a593Smuzhiyun * matches
43*4882a593Smuzhiyun *
44*4882a593Smuzhiyun * The algorithm is intended to only send "whole bytes", no bit-messing.
45*4882a593Smuzhiyun *
46*4882a593Smuzhiyun */
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun #include <config.h>
49*4882a593Smuzhiyun #include <jffs2/jffs2.h>
50*4882a593Smuzhiyun
rtime_decompress(unsigned char * data_in,unsigned char * cpage_out,u32 srclen,u32 destlen)51*4882a593Smuzhiyun void rtime_decompress(unsigned char *data_in, unsigned char *cpage_out,
52*4882a593Smuzhiyun u32 srclen, u32 destlen)
53*4882a593Smuzhiyun {
54*4882a593Smuzhiyun int positions[256];
55*4882a593Smuzhiyun int outpos;
56*4882a593Smuzhiyun int pos;
57*4882a593Smuzhiyun int i;
58*4882a593Smuzhiyun
59*4882a593Smuzhiyun outpos = pos = 0;
60*4882a593Smuzhiyun
61*4882a593Smuzhiyun for (i = 0; i < 256; positions[i++] = 0);
62*4882a593Smuzhiyun
63*4882a593Smuzhiyun while (outpos<destlen) {
64*4882a593Smuzhiyun unsigned char value;
65*4882a593Smuzhiyun int backoffs;
66*4882a593Smuzhiyun int repeat;
67*4882a593Smuzhiyun
68*4882a593Smuzhiyun value = data_in[pos++];
69*4882a593Smuzhiyun cpage_out[outpos++] = value; /* first the verbatim copied byte */
70*4882a593Smuzhiyun repeat = data_in[pos++];
71*4882a593Smuzhiyun backoffs = positions[value];
72*4882a593Smuzhiyun
73*4882a593Smuzhiyun positions[value]=outpos;
74*4882a593Smuzhiyun if (repeat) {
75*4882a593Smuzhiyun if (backoffs + repeat >= outpos) {
76*4882a593Smuzhiyun while(repeat) {
77*4882a593Smuzhiyun cpage_out[outpos++] = cpage_out[backoffs++];
78*4882a593Smuzhiyun repeat--;
79*4882a593Smuzhiyun }
80*4882a593Smuzhiyun } else {
81*4882a593Smuzhiyun for (i = 0; i < repeat; i++)
82*4882a593Smuzhiyun *(cpage_out + outpos + i) = *(cpage_out + backoffs + i);
83*4882a593Smuzhiyun outpos+=repeat;
84*4882a593Smuzhiyun }
85*4882a593Smuzhiyun }
86*4882a593Smuzhiyun }
87*4882a593Smuzhiyun }
88