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 #if (CONFIG_COMMANDS & CFG_CMD_JFFS2) 50 51 #include <jffs2/jffs2.h> 52 53 void rtime_decompress(unsigned char *data_in, unsigned char *cpage_out, 54 u32 srclen, u32 destlen) 55 { 56 int positions[256]; 57 int outpos; 58 int pos; 59 int i; 60 61 outpos = pos = 0; 62 63 for (i = 0; i < 256; positions[i++] = 0); 64 65 while (outpos<destlen) { 66 unsigned char value; 67 int backoffs; 68 int repeat; 69 70 value = data_in[pos++]; 71 cpage_out[outpos++] = value; /* first the verbatim copied byte */ 72 repeat = data_in[pos++]; 73 backoffs = positions[value]; 74 75 positions[value]=outpos; 76 if (repeat) { 77 if (backoffs + repeat >= outpos) { 78 while(repeat) { 79 cpage_out[outpos++] = cpage_out[backoffs++]; 80 repeat--; 81 } 82 } else { 83 for (i = 0; i < repeat; i++) 84 *(cpage_out + outpos + i) = *(cpage_out + backoffs + i); 85 outpos+=repeat; 86 } 87 } 88 } 89 } 90 91 #endif /* CFG_CMD_JFFS2 */ 92