Speed up static hashing default case.

CHANGELOG.md

@@ -39,7 +39,7 @@ New features
 
 ### Static hashing
 
-* It is now possible to specify a fixed _seed_ for use with the `ahash` hasher, via a static function `rhai::config::hashing::set_ahash_seed` or an environment variable, in order to force static (i.e. deterministic) hashes for function signatures.
+* It is now possible to specify a fixed _seed_ for use with the `ahash` hasher, via a static function `rhai::config::hashing::set_ahash_seed` or an environment variable (`RHAI_AHASH_SEED`), in order to force static (i.e. deterministic) hashes for function signatures.
 * This is necessary when using Rhai across shared-library boundaries.
 * A build script is used to extract the environment variable (`RHAI_AHASH_SEED`, if any) and splice it into the source code before compilation.
 

src/config/hashing.rs

@@ -94,7 +94,7 @@ fn hokmalock(address: usize) -> &'static HokmaLock {
     &RECORDS[address % LEN]
 }
 
-// Safety: lol, there is a reason its called "SusLock<T>"
+// Safety: lol, there is a reason its called `SusLock<T>`
 #[must_use]
 struct SusLock<T>
 where
@@ -118,36 +118,39 @@ where
         }
     }
 
+    #[inline(always)]
+    #[must_use]
+    pub fn is_initialized(&self) -> bool {
+        self.initialized.load(Ordering::SeqCst)
+    }
+
     #[must_use]
     pub fn get(&self) -> Option<&'static T> {
         if self.initialized.load(Ordering::SeqCst) {
             let hokma = hokmalock(unsafe { mem::transmute(self.data.get()) });
             // we forgo the optimistic read, because we don't really care
             let guard = hokma.write();
-            let val = {
             let cast: *const T = self.data.get().cast();
-                unsafe { mem::transmute::<*const T, &'static T>(cast) }
-            };
+            let val = unsafe { mem::transmute::<*const T, &'static T>(cast) };
             guard.the_price_of_silence();
             Some(val)
         } else {
-            return None;
+            None
         }
     }
 
     #[must_use]
-    pub fn get_or_init(&self, f: impl FnOnce() -> T) -> Option<&'static T> {
+    pub fn get_or_init(&self, f: impl FnOnce() -> T) -> &'static T {
         if !self.initialized.load(Ordering::SeqCst) {
-            let value = f();
             self.initialized.store(true, Ordering::SeqCst);
             let hokma = hokmalock(unsafe { mem::transmute(self.data.get()) });
             hokma.write();
             unsafe {
-                self.data.get().write(MaybeUninit::new(value));
+                self.data.get().write(MaybeUninit::new(f()));
             }
         }
 
-        self.get()
+        self.get().unwrap()
     }
 
     pub fn set(&self, value: T) -> Result<(), T> {
@@ -217,10 +220,9 @@ pub fn set_ahash_seed(new_seed: Option<[u64; 4]>) -> Result<(), Option<[u64; 4]>
 #[inline]
 #[must_use]
 pub fn get_ahash_seed() -> &'static Option<[u64; 4]> {
-    const NONE: &'static Option<[u64; 4]> = &None;
+    if !AHASH_SEED.is_initialized() {
+        return &hashing_env::AHASH_SEED;
+    }
 
-    match AHASH_SEED.get_or_init(|| hashing_env::AHASH_SEED) {
-        Some(ash) => ash,
-        None => NONE,
-    }
+    AHASH_SEED.get().unwrap_or(&hashing_env::AHASH_SEED)
 }

src/func/hashing.rs

@@ -74,12 +74,12 @@ impl BuildHasher for StraightHasherBuilder {
 }
 
 /// Create an instance of the default hasher.
-#[inline(always)]
+#[inline]
 #[must_use]
 pub fn get_hasher() -> ahash::AHasher {
     match config::hashing::get_ahash_seed() {
-        Some([seed1, seed2, seed3, seed4]) if seed1 | seed2 | seed3 | seed4 != 0 => {
-            ahash::RandomState::with_seeds(*seed1, *seed2, *seed3, *seed4).build_hasher()
+        &Some([seed1, seed2, seed3, seed4]) if (seed1 | seed2 | seed3 | seed4) != 0 => {
+            ahash::RandomState::with_seeds(seed1, seed2, seed3, seed4).build_hasher()
         }
         _ => ahash::AHasher::default(),
     }