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/*
* JFFS2 -- Journalling Flash File System, Version 2.
*
* Copyright (C) 2001 Red Hat, Inc.
*
* Created by Arjan van de Ven <arjanv@redhat.com>
*
* The original JFFS, from which the design for JFFS2 was derived,
* was designed and implemented by Axis Communications AB.
*
* The contents of this file are subject to the Red Hat eCos Public
* License Version 1.1 (the "Licence"); you may not use this file
* except in compliance with the Licence. You may obtain a copy of
* the Licence at http://www.redhat.com/
*
* Software distributed under the Licence is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.
* See the Licence for the specific language governing rights and
* limitations under the Licence.
*
* The Original Code is JFFS2 - Journalling Flash File System, version 2
*
* Alternatively, the contents of this file may be used under the
* terms of the GNU General Public License version 2 (the "GPL"), in
* which case the provisions of the GPL are applicable instead of the
* above. If you wish to allow the use of your version of this file
* only under the terms of the GPL and not to allow others to use your
* version of this file under the RHEPL, indicate your decision by
* deleting the provisions above and replace them with the notice and
* other provisions required by the GPL. If you do not delete the
* provisions above, a recipient may use your version of this file
* under either the RHEPL or the GPL.
*
* $Id: compr_rtime.c,v 1.2 2002/01/24 22:58:42 rfeany Exp $
*
*
* Very simple lz77-ish encoder.
*
* Theory of operation: Both encoder and decoder have a list of "last
* occurances" for every possible source-value; after sending the
* first source-byte, the second byte indicated the "run" length of
* matches
*
* The algorithm is intended to only send "whole bytes", no bit-messing.
*
*/
#include <config.h>
#include <jffs2/jffs2.h>
void rtime_decompress(unsigned char *data_in, unsigned char *cpage_out,
u32 srclen, u32 destlen)
{
int positions[256];
int outpos;
int pos;
int i;
outpos = pos = 0;
for (i = 0; i < 256; positions[i++] = 0);
while (outpos<destlen) {
unsigned char value;
int backoffs;
int repeat;
value = data_in[pos++];
cpage_out[outpos++] = value; /* first the verbatim copied byte */
repeat = data_in[pos++];
backoffs = positions[value];
positions[value]=outpos;
if (repeat) {
if (backoffs + repeat >= outpos) {
while(repeat) {
cpage_out[outpos++] = cpage_out[backoffs++];
repeat--;
}
} else {
for (i = 0; i < repeat; i++)
*(cpage_out + outpos + i) = *(cpage_out + backoffs + i);
outpos+=repeat;
}
}
}
}
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