From 4b46142f9043ce27adb77a34f364b5903bf35b3e Mon Sep 17 00:00:00 2001
From: mars <mars@tebibyte.media>
Date: Mon, 5 Dec 2022 21:26:05 -0700
Subject: [PATCH] Fix use of prehash so that the RAM cache actually hits

---
 src/backend/wasmtime.rs | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/backend/wasmtime.rs b/src/backend/wasmtime.rs
index 225fa07..a2bd075 100644
--- a/src/backend/wasmtime.rs
+++ b/src/backend/wasmtime.rs
@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
 use std::collections::{hash_map::DefaultHasher, HashMap};
-use std::hash::Hasher;
+use std::hash::{Hasher, BuildHasherDefault};
 use std::ops::DerefMut;
 use std::time::Instant;
 
@@ -11,12 +11,12 @@ use crate::DrawCommand;
 
 use canary_script::{Color, CursorEventKind, Rect, Vec2};
 use parking_lot::Mutex;
-use prehash::{DefaultPrehasher, Prehashed, Prehasher};
+use prehash::Passthru;
 
 type Caller<'a> = wasmtime::Caller<'a, Arc<ScriptAbi>>;
 type Store = wasmtime::Store<Arc<ScriptAbi>>;
 type Linker = wasmtime::Linker<Arc<ScriptAbi>>;
-type ModuleCache = Mutex<HashMap<Prehashed<u64>, wasmtime::Module, DefaultPrehasher>>;
+type ModuleCache = Mutex<HashMap<u64, wasmtime::Module, BuildHasherDefault<Passthru>>>;
 
 pub struct WasmtimeBackend {
     engine: wasmtime::Engine,
@@ -52,25 +52,22 @@ impl Backend for WasmtimeBackend {
 
         let mut hasher = DefaultHasher::new();
         hasher.write(module);
-        let hashed = hasher.finish();
-        let fmt_hash = format!("{:x}", hashed);
+        let hash = hasher.finish();
+        let fmt_hash = format!("{:x}", hash);
 
         log::debug!("Loading module (hash: {})", fmt_hash);
-
-        let prehasher = DefaultPrehasher::new();
-        let prehashed = prehasher.prehash(hashed);
         let mut cache = self.module_cache.lock();
 
-        let module = if let Some(module) = cache.get(&prehashed) {
+        let module = if let Some(module) = cache.get(&hash) {
             log::debug!("Module load cache hit (hash: {})", fmt_hash);
             module
         } else {
             log::debug!("Module load cache miss; building (hash: {})", fmt_hash);
             let start = Instant::now();
             let module = wasmtime::Module::new(&self.engine, module)?;
-            cache.insert(prehashed, module);
+            cache.insert(hash, module);
             log::debug!("Built module in {:?} (hash: {})", start.elapsed(), fmt_hash);
-            cache.get(&prehashed).unwrap()
+            cache.get(&hash).unwrap()
         };
 
         let mut store = wasmtime::Store::new(&self.engine, abi);