lzlocal.h

LZSS 压缩/解压算法 算法简单

/***************************************************************************
*          Lempel, Ziv, Storer, and Szymanski Encoding and Decoding
*
*   File    : lzlocal.h
*   Purpose : Internal headers for LZSS encode and decode routines.
*             Contains the prototypes to be used by the different match
*             finding algorithms.
*   Author  : Michael Dipperstein
*   Date    : February 18, 2004
*
****************************************************************************
*   UPDATES
*
*   $Id: lzlocal.h,v 1.3 2005/12/28 05:58:52 michael Exp $
*   $Log: lzlocal.h,v $
*   Revision 1.3  2005/12/28 05:58:52  michael
*   Add Wrap macro to replace mod when value is less than twice the limit.
*
*   Revision 1.2  2004/11/08 05:54:18  michael
*   1. Split encode and decode routines for smarter linking
*   2. Renamed lzsample.c sample.c to match my other samples
*   3. Makefile now builds code as libraries for better LGPL compliance.
*
*   Revision 1.1  2004/02/22 17:32:40  michael
*   Initial revision of header files for sliding window search implementations.
*
*
****************************************************************************
*
* LZSS: An ANSI C LZSS Encoding/Decoding Routine
* Copyright (C) 2004 by Michael Dipperstein ([e-mail])
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*
***************************************************************************/
#ifndef _LZSS_LOCAL_H
#define _LZSS_LOCAL_H

/***************************************************************************
*                             INCLUDED FILES
***************************************************************************/
#include <limits.h>

/***************************************************************************
*                                CONSTANTS
***************************************************************************/
#define FALSE   0
#define TRUE    1

#define OFFSET_BITS     12
#define LENGTH_BITS     4

#if (((1 << (OFFSET_BITS + LENGTH_BITS)) - 1) > UINT_MAX)
#error "Size of encoded data must not exceed the size of an unsigned int"
#endif

/* We want a sliding window*/
#define WINDOW_SIZE     (1 << OFFSET_BITS)

/* maximum match length not encoded and maximum length encoded (4 bits) */
#define MAX_UNCODED     2
#define MAX_CODED       ((1 << LENGTH_BITS) + MAX_UNCODED)

#define ENCODED     0       /* encoded string */
#define UNCODED     1       /* unencoded character */

/***************************************************************************
*                            TYPE DEFINITIONS
***************************************************************************/

/***************************************************************************
* This data structure stores an encoded string in (offset, length) format.
* The actual encoded string is stored using OFFSET_BITS for the offset and
* LENGTH_BITS for the length.
***************************************************************************/
typedef struct encoded_string_t
{
    unsigned int offset;    /* offset to start of longest match */
    unsigned int length;    /* length of longest match */
} encoded_string_t;

/***************************************************************************
*                                 MACROS
***************************************************************************/
/* wraps array index within array bounds (assumes value < 2 * limit) */
#define Wrap(value, limit)      (((value) < (limit)) ? (value) : ((value) - (limit)))

/***************************************************************************
*                               PROTOTYPES
***************************************************************************/
void InitializeSearchStructures(void);

encoded_string_t FindMatch(unsigned int windowHead, unsigned int uncodedHead);

void ReplaceChar(unsigned int charIndex, unsigned char replacement);

#endif      /* ndef _LZSS_LOCAL_H */