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/*
* shrink_context.h - compression context 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 _SHRINK_CONTEXT_H
#define _SHRINK_CONTEXT_H
#include "divsufsort.h"
#ifdef __cplusplus
extern "C" {
#endif
#define LCP_BITS 14
#define TAG_BITS 4
#define LCP_MAX ((1U<<(LCP_BITS - TAG_BITS)) - 1)
#define LCP_AND_TAG_MAX (1U<<(LCP_BITS - 1))
#define LCP_SHIFT (31-LCP_BITS)
#define LCP_MASK (((1U<<LCP_BITS) - 1) << LCP_SHIFT)
#define POS_MASK ((1U<<LCP_SHIFT) - 1)
#define VISITED_FLAG 0x80000000
#define EXCL_VISITED_MASK 0x7fffffff
#define NARRIVALS_PER_POSITION_V1 8
#define NARRIVALS_PER_POSITION_V2_SMALL 9
#define NARRIVALS_PER_POSITION_V2_BIG 32
#define ARRIVALS_PER_POSITION_SHIFT 5
#define NMATCHES_PER_INDEX_V1 8
#define MATCHES_PER_INDEX_SHIFT_V1 3
#define NMATCHES_PER_INDEX_V2 64
#define MATCHES_PER_INDEX_SHIFT_V2 6
#define LEAVE_ALONE_MATCH_SIZE 300
#define LEAVE_ALONE_MATCH_SIZE_SMALL 1000
#define MODESWITCH_PENALTY 3
/** One match */
typedef struct _lzsa_match {
unsigned short length;
unsigned short offset;
} lzsa_match;
/** Forward arrival slot */
typedef struct {
int cost;
unsigned short rep_offset;
short from_slot;
int from_pos;
unsigned short rep_len;
unsigned short match_len;
int rep_pos;
int num_literals;
int score;
} lzsa_arrival;
/** Compression statistics */
typedef struct _lzsa_stats {
int min_literals;
int max_literals;
int total_literals;
int min_offset;
int max_offset;
int num_rep_offsets;
int total_offsets;
int min_match_len;
int max_match_len;
int total_match_lens;
int min_rle1_len;
int max_rle1_len;
int total_rle1_lens;
int min_rle2_len;
int max_rle2_len;
int total_rle2_lens;
int literals_divisor;
int match_divisor;
int rle1_divisor;
int rle2_divisor;
} lzsa_stats;
/** Compression context */
typedef struct _lzsa_compressor {
divsufsort_ctx_t divsufsort_context;
unsigned int *intervals;
unsigned int *pos_data;
unsigned int *open_intervals;
lzsa_match *match;
lzsa_match *best_match;
lzsa_match *improved_match;
lzsa_arrival *arrival;
char *rep_handled_mask;
int *first_offset_for_byte;
int *next_offset_for_pos;
int min_match_size;
int format_version;
int flags;
int safe_dist;
int num_commands;
lzsa_stats stats;
} lzsa_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(lzsa_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(lzsa_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_compressor_shrink_block(lzsa_compressor *pCompressor, 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(lzsa_compressor *pCompressor);
#ifdef __cplusplus
}
#endif
#endif /* _SHRINK_CONTEXT_H */
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