/* * 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 1.5 2001/03/15 15:38:23 dwmw2 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 <linux/kernel.h>#include <linux/types.h>#include <linux/errno.h>#include <linux/string.h> /* _compress returns the compressed size, -1 if bigger */int rtime_compress(unsigned char *data_in, unsigned char *cpage_out, 		   __u32 *sourcelen, __u32 *dstlen){	int positions[256];	int outpos = 0;	int pos=0;	memset(positions,0,sizeof(positions)); 		while (pos < (*sourcelen) && outpos <= (*dstlen)-2) {		int backpos, runlen=0;		unsigned char value;				value = data_in[pos];		cpage_out[outpos++] = data_in[pos++];				backpos = positions[value];		positions[value]=pos;				while ((backpos < pos) && (pos < (*sourcelen)) &&		       (data_in[pos]==data_in[backpos++]) && (runlen<255)) {			pos++;			runlen++;		}		cpage_out[outpos++] = runlen;	}	if (outpos >= pos) {		/* We failed */		return -1;	}		/* Tell the caller how much we managed to compress, and how much space it took */	*sourcelen = pos;	*dstlen = outpos;	return 0;}		   void rtime_decompress(unsigned char *data_in, unsigned char *cpage_out,		      __u32 srclen, __u32 destlen){	int positions[256];	int outpos = 0;	int pos=0;		memset(positions,0,sizeof(positions)); 		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 {				memcpy(&cpage_out[outpos],&cpage_out[backoffs],repeat);				outpos+=repeat;					}		}	}		}