Use an object pool for ZopfliHash instances

Cargo.toml

@@ -24,6 +24,8 @@ crc32fast = { version = "1.4.0", default-features = false, optional = true }
 simd-adler32 = { version = "0.3.7", default-features = false, optional = true }
 typed-arena = { version = "2.0.2", default-features = false }
 log = "0.4.21"
+lockfree-object-pool = "0.1.5"
+once_cell = "1.19.0"
 
 [dev-dependencies]
 proptest = "1.4.0"

src/hash.rs

@@ -4,6 +4,9 @@ use alloc::{
 };
 use core::ptr::{addr_of, addr_of_mut, NonNull};
 
+use lockfree_object_pool::LinearObjectPool;
+use once_cell::sync::Lazy;
+
 use crate::util::{ZOPFLI_MIN_MATCH, ZOPFLI_WINDOW_MASK, ZOPFLI_WINDOW_SIZE};
 
 const HASH_SHIFT: i32 = 5;
@@ -176,3 +179,6 @@ impl ZopfliHash {
         }
     }
 }
+
+pub static HASH_POOL: Lazy<LinearObjectPool<Box<ZopfliHash>>> =
+    Lazy::new(|| LinearObjectPool::new(ZopfliHash::new, |boxed| boxed.reset()));

src/lib.rs

@@ -71,6 +71,8 @@ use std::io::{Error, Write};
 #[cfg(any(doc, not(feature = "std")))]
 pub use io::{Error, ErrorKind, Write};
 
+use crate::hash::HASH_POOL;
+
 /// Options for the Zopfli compression algorithm.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[cfg_attr(all(test, feature = "std"), derive(proptest_derive::Arbitrary))]
@@ -169,6 +171,12 @@ pub fn compress<R: std::io::Read, W: Write>(
     }
 }
 
+/// Populates object pools for expensive objects that Zopfli uses. Call this on a background thread
+/// when you know ahead of time that compression will be needed.
+pub fn prewarm_object_pools() {
+    HASH_POOL.pull();
+}
+
 #[cfg(all(test, feature = "std"))]
 mod test {
     use std::io;

src/lz77.rs

@@ -3,7 +3,7 @@ use core::cmp;
 
 use crate::{
     cache::Cache,
-    hash::{Which, ZopfliHash},
+    hash::{Which, ZopfliHash, HASH_POOL},
     symbols::{get_dist_symbol, get_length_symbol},
     util::{
         boxed_array, ZOPFLI_MAX_CHAIN_HITS, ZOPFLI_MAX_MATCH, ZOPFLI_MIN_MATCH, ZOPFLI_NUM_D,
@@ -139,7 +139,8 @@ impl Lz77Store {
             return;
         }
         let windowstart = instart.saturating_sub(ZOPFLI_WINDOW_SIZE);
-        let mut h = ZopfliHash::new();
+        let hash_pool = &*HASH_POOL;
+        let mut h = hash_pool.pull();
 
         let arr = &in_data[..inend];
         h.warmup(arr, windowstart, inend);
@@ -239,7 +240,8 @@ impl Lz77Store {
             return;
         }
 
-        let mut h = ZopfliHash::new();
+        let hash_pool = &*HASH_POOL;
+        let mut h = hash_pool.pull();
 
         let arr = &in_data[..inend];
         h.warmup(arr, windowstart, inend);

src/squeeze.rs

@@ -15,7 +15,7 @@ use log::{debug, trace};
 use crate::{
     cache::Cache,
     deflate::{calculate_block_size, BlockType},
-    hash::ZopfliHash,
+    hash::{ZopfliHash, HASH_POOL},
     lz77::{find_longest_match, LitLen, Lz77Store},
     symbols::{get_dist_extra_bits, get_dist_symbol, get_length_extra_bits, get_length_symbol},
     util::{ZOPFLI_MAX_MATCH, ZOPFLI_NUM_D, ZOPFLI_NUM_LL, ZOPFLI_WINDOW_MASK, ZOPFLI_WINDOW_SIZE},
@@ -421,7 +421,8 @@ pub fn lz77_optimal_fixed<C: Cache>(
     inend: usize,
     store: &mut Lz77Store,
 ) {
-    let mut h = ZopfliHash::new();
+    let hash_pool = &*HASH_POOL;
+    let mut h = hash_pool.pull();
     let mut costs = Vec::with_capacity(inend - instart);
     lz77_optimal_run(
         lmc,
@@ -455,7 +456,8 @@ pub fn lz77_optimal<C: Cache>(
     let mut stats = SymbolStats::default();
     stats.get_statistics(&currentstore);
 
-    let mut h = ZopfliHash::new();
+    let hash_pool = &*HASH_POOL;
+    let mut h = hash_pool.pull();
     let mut costs = Vec::with_capacity(inend - instart + 1);
 
     let mut beststats = SymbolStats::default();