Make State::max_chain_length u16

Author: brianpane

zlib-rs/src/deflate.rs

@@ -797,7 +797,7 @@ fn lm_set_level(state: &mut State, level: i8) {
     state.max_lazy_match = CONFIGURATION_TABLE[level as usize].max_lazy as usize;
     state.good_match = CONFIGURATION_TABLE[level as usize].good_length as usize;
     state.nice_match = CONFIGURATION_TABLE[level as usize].nice_length as usize;
-    state.max_chain_length = CONFIGURATION_TABLE[level as usize].max_chain as usize;
+    state.max_chain_length = CONFIGURATION_TABLE[level as usize].max_chain;
 
     state.hash_calc_variant = HashCalcVariant::for_max_chain_length(state.max_chain_length);
     state.level = level;
@@ -813,7 +813,7 @@ pub fn tune(
     stream.state.good_match = good_length;
     stream.state.max_lazy_match = max_lazy;
     stream.state.nice_match = nice_length;
-    stream.state.max_chain_length = max_chain;
+    stream.state.max_chain_length = max_chain as u16;
 
     ReturnCode::Ok
 }
@@ -1263,7 +1263,7 @@ pub(crate) struct State<'a> {
 
     /// To speed up deflation, hash chains are never searched beyond this length.
     /// A higher limit improves compression ratio but degrades the speed.
-    pub(crate) max_chain_length: usize,
+    pub(crate) max_chain_length: u16,
 
     // TODO untangle this mess! zlib uses the same field differently based on compression level
     // we should just have 2 fields for clarity!

zlib-rs/src/deflate/hash_calc.rs

@@ -9,7 +9,7 @@ pub enum HashCalcVariant {
 impl HashCalcVariant {
     /// Use rolling hash for deflate_slow algorithm with level 9. It allows us to
     /// properly lookup different hash chains to speed up longest_match search.
-    pub fn for_max_chain_length(max_chain_length: usize) -> Self {
+    pub fn for_max_chain_length(max_chain_length: u16) -> Self {
         if max_chain_length > 1024 {
             HashCalcVariant::Roll
         } else {

zlib-rs/src/deflate/longest_match.rs

@@ -26,7 +26,7 @@ fn longest_match_help<const SLOW: bool>(
     let limit_base: Pos;
     let early_exit: bool;
 
-    let mut chain_length: usize;
+    let mut chain_length: u16;
     let mut best_len: usize;
 
     let lookahead = state.lookahead;