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/*
* Copyright (c) 2003-2005 The Regents of The University of Michigan
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __LZSS_COMPRESSION_HH__
#define __LZSS_COMPRESSION_HH__
/** @file
* LZSSCompression declarations.
*/
#include "sim/host.hh" // for uint8_t
/**
* Simple LZSS compression scheme.
*/
class LZSSCompression
{
/**
* Finds the longest substring for the given offset.
* @param src The source block that we search for substrings.
* @param back The larger offset.
* @param size The size of the source block.
* @param L The length of the largest substring.
* @param P The starting offset of the largest substring.
*/
void findSubString(uint8_t *src, int back, int size, uint16_t &L,
uint16_t &P);
/**
* Emit an encoded byte to the compressed data array. If the 2 high
* order bits can be signed extended, use 1 byte encoding, if not use 2
* bytes.
* @param dest The compressed data.
* @param byte The byte to emit.
* @return The number of bytes used to encode.
*/
int emitByte(uint8_t *dest, uint8_t byte);
/**
* Emit a string reference to the compressed data array. A string reference
* always uses 3 bytes. 1 flag bit, 12 bits for the starting position, and
* 11 bits for the length of the string. This allows compression of 4096
* byte blocks with string lengths of up to 2048 bytes.
* @param dest The compressed data.
* @param P The starting position in the uncompressed data.
* @param L The length in bytes of the string.
*/
void emitString(uint8_t *dest, uint16_t P, uint16_t L);
public:
/**
* Compresses the source block and stores it in the destination block. If
* the compressed block grows to larger than the source block, it aborts
* and just performs a copy.
* @param dest The destination block.
* @param src The block to be compressed.
* @param size The size of the source block.
* @return The size of the compressed block.
*
* @pre Destination has enough storage to hold the compressed block.
*/
int compress(uint8_t *dest, uint8_t *src, int size);
/**
* Unompresses the source block and stores it in the destination block.
* @param dest The destination block.
* @param src The block to be uncompressed.
* @param size The size of the source block.
* @return The size of the uncompressed block.
*
* @pre Destination has enough storage to hold the uncompressed block.
*/
int uncompress(uint8_t *dest, uint8_t *src, int size);
};
#endif //__LZSS_COMPRESSION_HH__
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