From f6b671de6a08340c454449185655284f8078a53d Mon Sep 17 00:00:00 2001
From: Claudio Russo <claudio@dfinity.org>
Date: Fri, 16 Feb 2024 15:18:14 +0000
Subject: [PATCH] simplify hash to just use low 28 bits

---
 collections/motoko/src/ZhenyaHashmap.mo | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/collections/motoko/src/ZhenyaHashmap.mo b/collections/motoko/src/ZhenyaHashmap.mo
index 19b7d8df..4547e1c0 100644
--- a/collections/motoko/src/ZhenyaHashmap.mo
+++ b/collections/motoko/src/ZhenyaHashmap.mo
@@ -9,7 +9,12 @@ import Prim "mo:prim";
 actor {
     stable let profiling = Profiling.init();
 
-    let hash : HashMap.HashUtils<Nat64> = HashMap.n64hash;
+    let public func hashNat64(key: Nat64): Nat32 {
+      Prim.nat64ToNat32(key & 0x0fff_ffff);
+    };
+
+    let hash : HashMap.HashUtils<Nat64> = (hashNat64, func (x,y) = x == y);
+
     stable var map = HashMap.new<Nat64, Nat64>();
     let rand = Random.new(null, 42);