lzsa/src/lib.h

/*
 * lib.h - LZSA library definitions
 *
 * Copyright (C) 2019 Emmanuel Marty
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

/*
 * Uses the libdivsufsort library Copyright (c) 2003-2008 Yuta Mori
 *
 * Inspired by LZ4 by Yann Collet. https://github.com/lz4/lz4
 * With help, ideas, optimizations and speed measurements by spke <zxintrospec@gmail.com>
 * With ideas from Lizard by Przemyslaw Skibinski and Yann Collet. https://github.com/inikep/lizard
 * Also with ideas from smallz4 by Stephan Brumme. https://create.stephan-brumme.com/smallz4/
 *
 */

#ifndef _LIB_H
#define _LIB_H

#include "divsufsort.h"

/* Compression flags */
#define LZSA_FLAG_FAVOR_RATIO    (1<<0)      /**< 1 to compress with the best ratio, 0 to trade some compression ratio for extra decompression speed */
#define LZSA_FLAG_RAW_BLOCK      (1<<1)      /**< 1 to emit raw block */

#define LCP_BITS 15
#define LCP_MAX (1<<(LCP_BITS - 1))
#define LCP_SHIFT (32-LCP_BITS)
#define LCP_MASK (((1<<LCP_BITS) - 1) << LCP_SHIFT)
#define POS_MASK ((1<<LCP_SHIFT) - 1)

#define NMATCHES_PER_OFFSET 8
#define MATCHES_PER_OFFSET_SHIFT 3

#define LEAVE_ALONE_MATCH_SIZE 1000

#define LAST_MATCH_OFFSET 4
#define LAST_LITERALS 1

#define MODESWITCH_PENALTY 1

/** One match */
typedef struct _lzsa_match {
   unsigned short length;
   unsigned short offset;
} lzsa_match;

typedef struct _lzsa_repmatch_opt {
   int incoming_offset;
   short best_slot_for_incoming;
   short expected_repmatch;
} lzsa_repmatch_opt;

/** Compression context */
typedef struct _lsza_compressor {
   divsufsort_ctx_t divsufsort_context;
   unsigned int *intervals;
   unsigned int *pos_data;
   unsigned int *open_intervals;
   lzsa_match *match;
   lzsa_match *best_match;
   int *slot_cost;
   lzsa_repmatch_opt *repmatch_opt;
   int min_match_size;
   int format_version;
   int flags;
   int num_commands;
} lsza_compressor;

/**
 * Initialize compression context
 *
 * @param pCompressor compression context to initialize
 * @param nMaxWindowSize maximum size of input data window (previously compressed bytes + bytes to compress)
 * @param nMinMatchSize minimum match size (cannot be less than MIN_MATCH_SIZE)
 * @param nFlags compression flags
 *
 * @return 0 for success, non-zero for failure
 */
int lzsa_compressor_init(lsza_compressor *pCompressor, const int nMaxWindowSize, const int nMinMatchSize, const int nFormatVersion, const int nFlags);

/**
 * Clean up compression context and free up any associated resources
 *
 * @param pCompressor compression context to clean up
 */
void lzsa_compressor_destroy(lsza_compressor *pCompressor);

/**
 * Compress one block of data
 *
 * @param pCompressor compression context
 * @param pInWindow pointer to input data window (previously compressed bytes + bytes to compress)
 * @param nPreviousBlockSize number of previously compressed bytes (or 0 for none)
 * @param nInDataSize number of input bytes to compress
 * @param pOutData pointer to output buffer
 * @param nMaxOutDataSize maximum size of output buffer, in bytes
 *
 * @return size of compressed data in output buffer, or -1 if the data is uncompressible
 */
int lzsa_shrink_block(lsza_compressor *pCompressor, const unsigned char *pInWindow, const int nPreviousBlockSize, const int nInDataSize, unsigned char *pOutData, const int nMaxOutDataSize);

/**
 * Get the number of compression commands issued in compressed data blocks
 *
 * @return number of commands
 */
int lzsa_compressor_get_command_count(lsza_compressor *pCompressor);

/**
 * Decompress one data block
 *
 * @param pInBlock pointer to compressed data
 * @param nInBlockSize size of compressed data, in bytes
 * @param pOutData pointer to output decompression buffer (previously decompressed bytes + room for decompressing this block)
 * @param nOutDataOffset starting index of where to store decompressed bytes in output buffer (and size of previously decompressed bytes)
 * @param nBlockMaxSize total size of output decompression buffer, in bytes
 *
 * @return size of decompressed data in bytes, or -1 for error
 */
int lzsa_expand_block(const int nFormatVersion, const unsigned char *pInBlock, int nBlockSize, unsigned char *pOutData, int nOutDataOffset, int nBlockMaxSize);

#endif /* _LIB_H */