early-access version 3088

externals/vcpkg/buildtrees/boost-unordered/src/ost-1.79.0-d62a8023ae.clean/examples/fnv1.hpp

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+
+// Copyright 2008-2009 Daniel James.
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// This code is also released into the public domain.
+
+// Algorithm from: http://www.isthe.com/chongo/tech/comp/fnv/
+
+#include <string>
+
+namespace hash
+{
+    template <std::size_t FnvPrime, std::size_t OffsetBasis>
+    struct basic_fnv_1
+    {
+        std::size_t operator()(std::string const& text) const
+        {
+            std::size_t hash = OffsetBasis;
+            for(std::string::const_iterator it = text.begin(), end = text.end();
+                    it != end; ++it)
+            {
+                hash *= FnvPrime;
+                hash ^= *it;
+            }
+
+            return hash;
+        }
+    };
+
+    template <std::size_t FnvPrime, std::size_t OffsetBasis>
+    struct basic_fnv_1a
+    {
+        std::size_t operator()(std::string const& text) const
+        {
+            std::size_t hash = OffsetBasis;
+            for(std::string::const_iterator it = text.begin(), end = text.end();
+                    it != end; ++it)
+            {
+                hash ^= *it;
+                hash *= FnvPrime;
+            }
+
+            return hash;
+        }
+    };
+
+    // For 32 bit machines:
+    const std::size_t fnv_prime = 16777619u;
+    const std::size_t fnv_offset_basis = 2166136261u;
+
+    // For 64 bit machines:
+    // const std::size_t fnv_prime = 1099511628211u;
+    // const std::size_t fnv_offset_basis = 14695981039346656037u;
+
+    // For 128 bit machines:
+    // const std::size_t fnv_prime = 309485009821345068724781401u;
+    // const std::size_t fnv_offset_basis =
+    //     275519064689413815358837431229664493455u;
+
+    // For 256 bit machines:
+    // const std::size_t fnv_prime =
+    //     374144419156711147060143317175368453031918731002211u;
+    // const std::size_t fnv_offset_basis =
+    //     100029257958052580907070968620625704837092796014241193945225284501741471925557u;
+
+    typedef basic_fnv_1<fnv_prime, fnv_offset_basis> fnv_1;
+    typedef basic_fnv_1a<fnv_prime, fnv_offset_basis> fnv_1a;
+}