zxc_lz77_params_t Struct Reference

Search parameters for LZ77 compression levels. More...

#include <zxc_internal.h>

Data Fields
int	search_depth
	Maximum number of candidates explored in the hash chain per position.
int	sufficient_len
	"Good enough" match length: once a match reaches this threshold the chain walk stops immediately, avoiding wasted effort on an already excellent match.
int	use_lazy
	Enable lazy matching.
int	lazy_attempts
	Maximum number of candidates explored during lazy evaluation (same semantics as search_depth but applied to the ip+1 / ip+2 probes).
int	lazy_len_threshold
	Skip lazy evaluation when the current match length already reaches this threshold: a match this long is unlikely to be beaten at the next byte.
uint32_t	step_base
	Base step size when advancing through unmatched literals.
uint32_t	step_shift
	Acceleration factor for step size: step = step_base + (distance >> step_shift).
uint32_t	min_offset
	Shortest match distance the parser may emit; 1 = unconstrained.
uint8_t	split_max
	Longest match re-emitted as inline pieces (zxc_glo_split_block), in the token's units (length - ZXC_LZ_MIN_MATCH_LEN); <= ZXC_GLO_INLINE_ML_CODE disables.

Detailed Description

Search parameters for LZ77 compression levels.

Each compression level maps to a specific set of parameters that control the trade-off between compression speed and ratio. Higher search depths and lazy matching improve ratio at the expense of throughput; larger step values accelerate literal scanning but may miss short matches.

Definition at line 1108 of file zxc_internal.h.

Field Documentation

lazy_attempts

int zxc_lz77_params_t::lazy_attempts

Maximum number of candidates explored during lazy evaluation (same semantics as search_depth but applied to the ip+1 / ip+2 probes).

Only meaningful when use_lazy is non-zero.

Definition at line 1127 of file zxc_internal.h.

Referenced by zxc_lazy_probe().

lazy_len_threshold

int zxc_lz77_params_t::lazy_len_threshold

Skip lazy evaluation when the current match length already reaches this threshold: a match this long is unlikely to be beaten at the next byte.

Set to 0 when use_lazy is disabled.

Definition at line 1132 of file zxc_internal.h.

Referenced by zxc_lz77_find_best_match().

min_offset

uint32_t zxc_lz77_params_t::min_offset

Shortest match distance the parser may emit; 1 = unconstrained.

Skipped candidates do not end the chain walk, which continues to a legal one further back. See ZXC_LZ_MINDIST.

Definition at line 1146 of file zxc_internal.h.

Referenced by zxc_encode_block_ghi(), zxc_encode_block_glo(), zxc_lazy_probe(), and zxc_lz77_find_best_match().

search_depth

int zxc_lz77_params_t::search_depth

Maximum number of candidates explored in the hash chain per position.

Higher values find better matches but increase CPU cost linearly.

Definition at line 1111 of file zxc_internal.h.

Referenced by zxc_lz77_find_best_match().

split_max

uint8_t zxc_lz77_params_t::split_max

Longest match re-emitted as inline pieces (zxc_glo_split_block), in the token's units (length - ZXC_LZ_MIN_MATCH_LEN); <= ZXC_GLO_INLINE_ML_CODE disables.

GLO levels only.

Definition at line 1151 of file zxc_internal.h.

Referenced by zxc_encode_block_glo().

step_base

uint32_t zxc_lz77_params_t::step_base

Base step size when advancing through unmatched literals.

1 = test every byte (best ratio), 4 = skip aggressively (fastest).

Definition at line 1136 of file zxc_internal.h.

Referenced by zxc_encode_block_ghi(), and zxc_encode_block_glo().

step_shift

uint32_t zxc_lz77_params_t::step_shift

Acceleration factor for step size: step = step_base + (distance >> step_shift).

A larger value keeps the step conservative (grows slowly with distance); a smaller value ramps up quickly, skipping more in long literal runs.

Definition at line 1141 of file zxc_internal.h.

Referenced by zxc_encode_block_ghi(), and zxc_encode_block_glo().

sufficient_len

int zxc_lz77_params_t::sufficient_len

"Good enough" match length: once a match reaches this threshold the chain walk stops immediately, avoiding wasted effort on an already excellent match.

Definition at line 1116 of file zxc_internal.h.

Referenced by zxc_lz77_find_best_match().

use_lazy

int zxc_lz77_params_t::use_lazy

Enable lazy matching.

When set, after finding a match at position ip the compressor probes ip+1 (and ip+2 for level >= 4) to see if a longer match exists. If so, a literal is emitted and the better match is taken instead. Improves ratio but costs extra work.

Definition at line 1122 of file zxc_internal.h.

Referenced by zxc_lz77_find_best_match(), and zxc_lz77_optimal_parse_glo().

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The documentation for this struct was generated from the following file:

• src/lib/zxc_internal.h