From f5a0210cdfba56fb26bcc1b51bfc5878802bf264 Mon Sep 17 00:00:00 2001
From: Nathan Vegdahl <cessen@cessen.com>
Date: Thu, 21 Jul 2022 12:15:36 -0700
Subject: [PATCH] More principled seeding approach in the hash functions.

---
 src/hash.rs | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/hash.rs b/src/hash.rs
index 49022a9..de535d4 100644
--- a/src/hash.rs
+++ b/src/hash.rs
@@ -1,35 +1,35 @@
 /// A fast seedable 32-bit hash function.
-///
-/// Based on <https://github.com/skeeto/hash-prospector>.
 pub fn hash_u32(mut n: u32, seed: u32) -> u32 {
     n ^= 0xe6fe3beb; // So zero doesn't map to zero.
     n ^= seed;
 
+    // From https://github.com/skeeto/hash-prospector
     n ^= n >> 16;
     n = n.wrapping_mul(0x21f0aaad);
-    n ^= seed;
     n ^= n >> 15;
     n = n.wrapping_mul(0xd35a2d97);
     n ^= n >> 15;
 
-    n
+    // We xor by `seed` again in case the first time cancelled out our
+    // "zero doesn't map to zero" precaution.
+    n ^ seed
 }
 
 /// A fast seedable 64-bit hash function.
-///
-/// Based on <https://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html>.
 pub fn hash_u64(mut n: u64, seed: u64) -> u64 {
     n ^= 0x4acc3f27cc712c9d; // So zero doesn't map to zero.
     n ^= seed;
 
+    // From https://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
     n ^= n >> 30;
     n = n.wrapping_mul(0xbf58476d1ce4e5b9);
-    n ^= seed;
     n ^= n >> 27;
     n = n.wrapping_mul(0x94d049bb133111eb);
     n ^= n >> 31;
 
-    n
+    // We xor by `seed` again in case the first time cancelled out our
+    // "zero doesn't map to zero" precaution.
+    n ^ seed
 }
 
 /// Returns a random float in [0, 1] based on 'n' and a seed.