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Hard-code the hash selection for the fast and medium deflate algorithms #373

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Merged
merged 1 commit into from
May 28, 2025
Merged

Hard-code the hash selection for the fast and medium deflate algorithms #373

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5 changes: 3 additions & 2 deletions zlib-rs/src/deflate/algorithm/fast.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
#![forbid(unsafe_code)]

use crate::deflate::hash_calc::StandardHashCalc;
use crate::{
deflate::{
fill_window, BlockState, DeflateStream, MIN_LOOKAHEAD, STD_MIN_MATCH, WANT_MIN_MATCH,
Expand Down Expand Up @@ -33,7 +34,7 @@ pub fn deflate_fast(stream: &mut DeflateStream, flush: DeflateFlush) -> BlockSta
// dictionary, and set hash_head to the head of the hash chain:

if state.lookahead >= WANT_MIN_MATCH {
let hash_head = state.quick_insert_string(state.strstart);
let hash_head = StandardHashCalc::quick_insert_string(state, state.strstart);
dist = state.strstart as isize - hash_head as isize;

/* Find the longest match, discarding those <= prev_length.
Expand Down Expand Up @@ -70,7 +71,7 @@ pub fn deflate_fast(stream: &mut DeflateStream, flush: DeflateFlush) -> BlockSta
state.strstart += match_len;
} else {
state.strstart += match_len;
state.quick_insert_string(state.strstart + 2 - STD_MIN_MATCH);
StandardHashCalc::quick_insert_string(state, state.strstart + 2 - STD_MIN_MATCH);

/* If lookahead < STD_MIN_MATCH, ins_h is garbage, but it does not
* matter since it will be recomputed at next deflate call.
Expand Down
7 changes: 4 additions & 3 deletions zlib-rs/src/deflate/algorithm/medium.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
#![forbid(unsafe_code)]

use crate::deflate::hash_calc::StandardHashCalc;
use crate::{
deflate::{
fill_window, BlockState, DeflateStream, State, MIN_LOOKAHEAD, STD_MIN_MATCH, WANT_MIN_MATCH,
Expand Down Expand Up @@ -60,7 +61,7 @@ pub fn deflate_medium(stream: &mut DeflateStream, flush: DeflateFlush) -> BlockS
} else {
hash_head = 0;
if state.lookahead >= WANT_MIN_MATCH {
hash_head = state.quick_insert_string(state.strstart);
hash_head = StandardHashCalc::quick_insert_string(state, state.strstart);
}

current_match.strstart = state.strstart as u16;
Expand Down Expand Up @@ -104,7 +105,7 @@ pub fn deflate_medium(stream: &mut DeflateStream, flush: DeflateFlush) -> BlockS
< (state.window_size - MIN_LOOKAHEAD)
{
state.strstart = (current_match.strstart + current_match.match_length) as usize;
hash_head = state.quick_insert_string(state.strstart);
hash_head = StandardHashCalc::quick_insert_string(state, state.strstart);

next_match.strstart = state.strstart as u16;
next_match.orgstart = next_match.strstart;
Expand Down Expand Up @@ -253,7 +254,7 @@ fn insert_match(state: &mut State, mut m: Match) {
m.match_length = 0;

if (m.strstart as usize) >= (STD_MIN_MATCH - 2) {
state.quick_insert_string(m.strstart as usize + 2 - STD_MIN_MATCH);
StandardHashCalc::quick_insert_string(state, m.strstart as usize + 2 - STD_MIN_MATCH);
}

/* If lookahead < WANT_MIN_MATCH, ins_h is garbage, but it does not
Expand Down
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