81882c0d10
base/compression/lzss_compression.cc:
base/compression/lzss_compression.hh:
Rework for better performance
--HG--
extra : convert_revision : b13d706e0e23cbe7122b611258354c66cf5f3c70
101 lines
4 KiB
C++
101 lines
4 KiB
C++
/*
|
|
* Copyright (c) 2003 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__
|