Squashed 'OpenVPN Adapter/Vendors/openvpn/' content from commit da99df6

git-subtree-dir: OpenVPN Adapter/Vendors/openvpn
git-subtree-split: da99df69492256d7a18bbea303ae98457782a4bf

openvpn/common/hash.hpp

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+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2017 OpenVPN Technologies, Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program 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 this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+
+#ifndef OPENVPN_COMMON_HASH_H
+#define OPENVPN_COMMON_HASH_H
+
+#include <cstring> // for std::strlen
+#include <cstdint> // for std::uint32_t, uint64_t
+#include <functional>
+
+#include <openvpn/common/size.hpp>
+
+#define OPENVPN_HASH_METHOD(T, meth)			\
+  namespace std {					\
+    template <>						\
+    struct hash<T>					\
+    {							\
+      inline std::size_t operator()(const T& obj) const	\
+      {							\
+        return obj.meth();				\
+      }							\
+    };							\
+  }
+
+namespace openvpn {
+  namespace Hash {
+
+    void combine_data(std::size_t& seed, const void *data, std::size_t size);
+
+    template <class T>
+    inline void combine(std::size_t& seed, const T& v)
+    {
+      std::hash<T> hasher;
+      seed ^= hasher(v) + 0x9e3779b9 + (seed<<6) + (seed>>2);
+    }
+
+    inline void combine(std::size_t& seed, const char *str)
+    {
+      combine_data(seed, str, std::strlen(str));
+    }
+
+    template<typename T, typename... Args>
+    inline void combine(std::size_t& seed, const T& first, Args... args)
+    {
+      combine(seed, first);
+      combine(seed, args...);
+    }
+
+    template<typename... Args>
+    inline std::size_t value(Args... args)
+    {
+      std::size_t hash = 0;
+      combine(hash, args...);
+      return hash;
+    }
+
+    // A hasher that combines a data hash with a stateful seed.
+    template <typename T>
+    class InitialSeed
+    {
+    public:
+      InitialSeed(std::size_t seed) : seed_(seed) {}
+
+      std::size_t operator()(const T& obj) const
+      {
+	std::size_t seed = seed_;
+	combine(seed, obj);
+	return seed;
+      }
+
+    private:
+      std::size_t seed_;
+    };
+
+    inline void combine_data(std::size_t& seed, const void *data, std::size_t size)
+    {
+      while (size >= sizeof(std::uint32_t))
+	{
+	  combine(seed, static_cast<const std::uint32_t*>(data)[0]);
+	  data = static_cast<const std::uint8_t*>(data) + sizeof(std::uint32_t);
+	  size -= sizeof(std::uint32_t);
+	}
+      switch (size)
+	{
+	case 1:
+	  combine(seed, static_cast<const std::uint8_t*>(data)[0]);
+	  break;
+	case 2:
+	  combine(seed, static_cast<const std::uint16_t*>(data)[0]);
+	  break;
+	case 3:
+	  combine(seed, static_cast<const std::uint16_t*>(data)[0]);
+	  combine(seed, static_cast<const std::uint8_t*>(data)[2]);
+	  break;
+	}
+    }
+  }
+}
+
+#endif