From 2ec12fe06f02deb31aec5dd29595c19359623098 Mon Sep 17 00:00:00 2001
From: Felix Riedel <felix.riedel@gmail.com>
Date: Fri, 25 Dec 2020 16:19:18 +0000
Subject: [PATCH] Improve hashing of numbers

Using an integer hash (https://stackoverflow.com/a/12996028/60617) on
the number casted to int32 combined with lower bits of the number.
---
 src/core/value.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/core/value.c b/src/core/value.c
index 1be7966c..79ce6f32 100644
--- a/src/core/value.c
+++ b/src/core/value.c
@@ -260,6 +260,16 @@ int32_t janet_hash(Janet x) {
             break;
         case JANET_STRUCT:
             hash = janet_struct_hash(janet_unwrap_struct(x));
+            break;
+        case JANET_NUMBER:
+            hash = (int32_t)janet_unwrap_number(x);
+            hash = ((hash >> 16) ^ hash) * 0x45d9f3b;
+            hash = ((hash >> 16) ^ hash) * 0x45d9f3b;
+            hash = (hash >> 16) ^ hash;
+
+            uint32_t lo = (uint32_t)(janet_u64(x) & 0xFFFFFFFF);
+            hash ^= lo + 0x9e3779b9 + (hash<<6) + (hash>>2);
+
             break;
         case JANET_ABSTRACT: {
             JanetAbstract xx = janet_unwrap_abstract(x);