From 56cb6a23261f34e2855c89c662b70030e89a2e77 Mon Sep 17 00:00:00 2001
From: Alex Fabijanic <alex@pocoproject.org>
Date: Wed, 31 Mar 2021 20:39:17 +0200
Subject: [PATCH] feat(HashRange): port HashRange from boost

---
 Foundation/include/Poco/Hash.h | 95 ++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/Foundation/include/Poco/Hash.h b/Foundation/include/Poco/Hash.h
index 7aafb66a6..69c09e138 100644
--- a/Foundation/include/Poco/Hash.h
+++ b/Foundation/include/Poco/Hash.h
@@ -10,6 +10,9 @@
 // Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
 // and Contributors.
 //
+// HashRange Copyright 2005-2014 Daniel James.
+// (Extracted from Boost 1.75.0 lib and adapted for poco on 2021-03-31)
+//
 // SPDX-License-Identifier:	BSL-1.0
 //
 
@@ -19,9 +22,17 @@
 
 
 #include "Poco/Foundation.h"
+#include "Poco/Types.h"
 #include <cstddef>
 
 
+#if defined(_MSC_VER)
+#   define POCO_HASH_ROTL32(x, r) _rotl(x,r)
+#else
+#   define POCO_HASH_ROTL32(x, r) (x << r) | (x >> (32 - r))
+#endif
+
+
 namespace Poco {
 
 
@@ -99,6 +110,90 @@ inline std::size_t hash(UInt64 n)
 }
 
 
+namespace Impl {
+
+
+template <typename SizeT>
+inline void HashCombine(SizeT& seed, SizeT value)
+{
+    seed ^= value + 0x9e3779b9 + (seed<<6) + (seed>>2);
+}
+
+
+inline void HashCombine(Poco::UInt32& h1, Poco::UInt32 k1)
+{
+    const uint32_t c1 = 0xcc9e2d51;
+    const uint32_t c2 = 0x1b873593;
+
+    k1 *= c1;
+    k1 = POCO_HASH_ROTL32(k1,15);
+    k1 *= c2;
+
+    h1 ^= k1;
+    h1 = POCO_HASH_ROTL32(h1,13);
+    h1 = h1*5+0xe6546b64;
+}
+
+
+#if defined(POCO_PTR_IS_64_BIT) && !(defined(__GNUC__) && ULONG_MAX == 0xffffffff)
+
+
+inline void HashCombine(Poco::UInt64& h, Poco::UInt64 k)
+{
+    const Poco::UInt64 m = UINT64_C(0xc6a4a7935bd1e995);
+    const int r = 47;
+
+    k *= m;
+    k ^= k >> r;
+    k *= m;
+
+    h ^= k;
+    h *= m;
+
+    // Completely arbitrary number, to
+    // prevent zeros from hashing to 0.
+    h += 0xe6546b64;
+}
+
+
+#endif // POCO_PTR_IS_64_BIT
+
+
+} // namespace Impl
+
+
+template <class T>
+inline void HashCombine(std::size_t& seed, T const& v)
+{
+    Hash<T> hasher;
+    Impl::HashCombine(seed, hasher(v));
+}
+
+
+template <class It>
+inline std::size_t HashRange(It first, It last)
+{
+    std::size_t seed = 0;
+
+    for(; first != last; ++first)
+    {
+        HashCombine<typename std::iterator_traits<It>::value_type>(seed, *first);
+    }
+
+    return seed;
+}
+
+
+template <class It>
+inline void HashRange(std::size_t& seed, It first, It last)
+{
+    for(; first != last; ++first)
+    {
+        HashCombine<typename std::iterator_traits<It>::value_type>(seed, *first);
+    }
+}
+
+
 } // namespace Poco