From 96a5bc950c7bd0b2cbd7c8b80f2c4c1f9843f39b Mon Sep 17 00:00:00 2001
From: Lynix <lynix680@gmail.com>
Date: Tue, 24 Feb 2015 20:00:13 +0100
Subject: [PATCH] Added HashCombine function

Former-commit-id: 852deae33143138f2841e226690bfef94d3ba2b9
---
 include/Nazara/Core/Algorithm.hpp |  2 ++
 include/Nazara/Core/Algorithm.inl | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/Nazara/Core/Algorithm.hpp b/include/Nazara/Core/Algorithm.hpp
index f094c8976..26c9efbcf 100644
--- a/include/Nazara/Core/Algorithm.hpp
+++ b/include/Nazara/Core/Algorithm.hpp
@@ -8,8 +8,10 @@
 #define NAZARA_ALGORITHM_CORE_HPP
 
 #include <Nazara/Prerequesites.hpp>
+#include <functional>
 #include <tuple>
 
+template<typename T> void NzHashCombine(std::size_t& seed, const T& v);
 template<typename F, typename... ArgsT> void NzUnpackTuple(F func, const std::tuple<ArgsT...>& t);
 
 #include <Nazara/Core/Algorithm.inl>
diff --git a/include/Nazara/Core/Algorithm.inl b/include/Nazara/Core/Algorithm.inl
index 5a8bbeccf..fa1a388ab 100644
--- a/include/Nazara/Core/Algorithm.inl
+++ b/include/Nazara/Core/Algorithm.inl
@@ -30,6 +30,23 @@ struct NzImplTupleUnpack<0>
 	}
 };
 
+// Algorithme venant de CityHash par Google
+// http://stackoverflow.com/questions/8513911/how-to-create-a-good-hash-combine-with-64-bit-output-inspired-by-boosthash-co
+template<typename T>
+void NzHashCombine(std::size_t& seed, const T& v)
+{
+    const std::size_t kMul = 0x9ddfea08eb382d69ULL;
+
+    std::hash<T> hasher;
+    std::size_t a = (hasher(v) ^ seed) * kMul;
+    a ^= (a >> 47);
+
+    std::size_t b = (seed ^ a) * kMul;
+    b ^= (b >> 47);
+
+    seed = b * kMul;
+}
+
 template<typename F, typename... ArgsT>
 void NzUnpackTuple(F func, const std::tuple<ArgsT...>& t)
 {