From 67104b4dc1d21a3079a20f244e7fc2274fe81dff Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Mon, 13 Jun 2022 01:08:03 +0100
Subject: [PATCH] Add a simple 32 bit to 32 bit hash function (MurmurHash3)

---
 src/core/CMakeLists.txt |  1 +
 src/core/hash_func.hpp  | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 src/core/hash_func.hpp

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index a11fe2a7aa..e2d433907e 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -11,6 +11,7 @@ add_files(
     endian_func.hpp
     endian_type.hpp
     enum_type.hpp
+    hash_func.hpp
     geometry_func.cpp
     geometry_func.hpp
     geometry_type.hpp
diff --git a/src/core/hash_func.hpp b/src/core/hash_func.hpp
new file mode 100644
index 0000000000..af526a45b8
--- /dev/null
+++ b/src/core/hash_func.hpp
@@ -0,0 +1,28 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file hash_func.hpp Functions related to hashing operations. */
+
+#ifndef HASH_FUNC_HPP
+#define HASH_FUNC_HPP
+
+/**
+ * Simple 32 bit to 32 bit hash
+ * From MurmurHash3
+ */
+inline uint32 SimpleHash32(uint32 h)
+{
+	h ^= h >> 16;
+	h *= 0x85ebca6b;
+	h ^= h >> 13;
+	h *= 0xc2b2ae35;
+	h ^= h >> 16;
+
+	return h;
+}
+
+#endif /* HASH_FUNC_HPP */