perf: Optimise from_rng impl for WyRand (#15)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wyrand"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2021"
 authors = ["Gonçalo Rica Pais da Silva <[email protected]>"]
 description = "A fast & portable non-cryptographic pseudorandom number generator and hashing algorithm"
@@ -35,6 +35,7 @@ serde = { version = "1.0", features = ["derive"], optional = true }
 [dev-dependencies]
 criterion = "0.5"
 serde_test = "1.0"
+rand = "0.8"
 
 [[bench]]
 name = "rand_bench"

benches/rand_bench.rs

@@ -1,7 +1,8 @@
 use criterion::{black_box, criterion_main, Criterion};
 
 fn wyrand_benchmark(c: &mut Criterion) {
-    use rand_core::RngCore;
+    use rand::thread_rng;
+    use rand_core::{RngCore, SeedableRng};
     use wyrand::WyRand;
 
     c.bench_function("rand", |b| {
@@ -29,6 +30,10 @@ fn wyrand_benchmark(c: &mut Criterion) {
             criterion::BatchSize::LargeInput,
         )
     });
+
+    c.bench_function("from_rng", |b| {
+        b.iter(|| black_box(WyRand::from_rng(thread_rng())))
+    });
 }
 
 #[cfg(feature = "wyhash")]

src/final_v4_2/wyrand.rs

@@ -92,9 +92,15 @@ impl RngCore for WyRand {
 impl SeedableRng for WyRand {
     type Seed = [u8; core::mem::size_of::<u64>()];
 
+    #[inline]
     fn from_seed(seed: Self::Seed) -> Self {
         Self::new(u64::from_ne_bytes(seed))
     }
+
+    #[inline]
+    fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, rand_core::Error> {
+       Ok(Self::new(rng.next_u64())) 
+    }
 }
 
 #[cfg(test)]
@@ -155,6 +161,16 @@ mod tests {
         assert_eq!(rand_dyn(&mut rng), 412_509_173);
     }
 
+    #[cfg(feature = "rand_core")]
+    #[test]
+    fn rand_core_from_rng() {
+        let mut source = WyRand::from_seed(Default::default());
+
+        let mut rng = WyRand::from_rng(&mut source).expect("from_rng should never fail here");
+
+        assert_eq!(rng.next_u32(), 844672934);
+    }
+
     #[cfg(all(feature = "serde1", feature = "debug"))]
     #[test]
     fn serde_tokens() {

src/legacy_final_v4/wyrand.rs

@@ -92,9 +92,15 @@ impl RngCore for WyRandLegacy {
 impl SeedableRng for WyRandLegacy {
     type Seed = [u8; core::mem::size_of::<u64>()];
 
+    #[inline]
     fn from_seed(seed: Self::Seed) -> Self {
         Self::new(u64::from_ne_bytes(seed))
     }
+
+    #[inline]
+    fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, rand_core::Error> {
+       Ok(Self::new(rng.next_u64())) 
+    }
 }
 
 #[cfg(test)]
@@ -155,6 +161,16 @@ mod tests {
         assert_eq!(rand_dyn(&mut rng), 4_283_336_045);
     }
 
+    #[cfg(feature = "rand_core")]
+    #[test]
+    fn rand_core_from_rng() {
+        let mut source = WyRandLegacy::from_seed(Default::default());
+
+        let mut rng = WyRandLegacy::from_rng(&mut source).expect("from_rng should never fail here");
+
+        assert_eq!(rng.next_u32(), 4242651740);
+    }
+
     #[cfg(all(feature = "serde1", feature = "debug"))]
     #[test]
     fn serde_tokens() {