LXR uboot/fs/jffs2/compr

   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
  51void 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