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 #ifndef BOOST_HASH2_SIPHASH_HPP_INCLUDED
 #define BOOST_HASH2_SIPHASH_HPP_INCLUDED
 
 // Copyright 2017, 2018 Peter Dimov.
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 //
 // SipHash, https://131002.net/siphash/
 
 #include <boost/hash2/detail/read.hpp>
 #include <boost/hash2/detail/rot.hpp>
 #include <boost/hash2/detail/memcpy.hpp>
 #include <boost/hash2/detail/memset.hpp>
 #include <boost/hash2/detail/config.hpp>
 #include <boost/assert.hpp>
 #include <cstdint>
 #include <cstring>
 #include <cstddef>
 
 namespace boost
 {
 namespace hash2
 {
 
 class siphash_64
 {
 private:
 
     std::uint64_t v0 = 0x736f6d6570736575ULL;
     std::uint64_t v1 = 0x646f72616e646f6dULL;
     std::uint64_t v2 = 0x6c7967656e657261ULL;
     std::uint64_t v3 = 0x7465646279746573ULL;
 
     unsigned char buffer_[ 8 ] = {};
     std::size_t m_ = 0; // == n_ % 8
 
     std::uint64_t n_ = 0;
 
 private:
 
     BOOST_CXX14_CONSTEXPR void sipround()
     {
         v0 += v1;
         v1 = detail::rotl(v1, 13);
         v1 ^= v0;
         v0 = detail::rotl(v0, 32);
         v2 += v3;
         v3 = detail::rotl(v3, 16);
         v3 ^= v2;
         v0 += v3;
         v3 = detail::rotl(v3, 21);
         v3 ^= v0;
         v2 += v1;
         v1 = detail::rotl(v1, 17);
         v1 ^= v2;
         v2 = detail::rotl(v2, 32);
     }
 
     BOOST_CXX14_CONSTEXPR void update_( unsigned char const * p )
     {
         std::uint64_t m = detail::read64le( p );
 
         v3 ^= m;
 
         sipround();
         sipround();
 
         v0 ^= m;
     }
 
 public:
 
     using result_type = std::uint64_t;
 
     siphash_64() = default;
 
     BOOST_CXX14_CONSTEXPR explicit siphash_64( std::uint64_t seed )
     {
         v0 ^= seed;
         v2 ^= seed;
     }
 
     BOOST_CXX14_CONSTEXPR siphash_64( unsigned char const * p, std::size_t n )
     {
         if( n == 16 )
         {
             std::uint64_t k0 = detail::read64le( p + 0 );
             std::uint64_t k1 = detail::read64le( p + 8 );
 
             v0 ^= k0;
             v1 ^= k1;
             v2 ^= k0;
             v3 ^= k1;
         }
         else if( n != 0 )
         {
             update( p, n );
             result();
         }
     }
 
     siphash_64( void const * p, std::size_t n ): siphash_64( static_cast<unsigned char const*>( p ), n )
     {
     }
 
     BOOST_CXX14_CONSTEXPR void update( unsigned char const* p, std::size_t n )
     {
         BOOST_ASSERT( m_ == n_ % 8 );
 
         if( n == 0 ) return;
 
         n_ += n;
 
         if( m_ > 0 )
         {
             std::size_t k = 8 - m_;
 
             if( n < k )
             {
                 k = n;
             }
 
             detail::memcpy( buffer_ + m_, p, k );
 
             p += k;
             n -= k;
             m_ += k;
 
             if( m_ < 8 ) return;
 
             BOOST_ASSERT( m_ == 8 );
 
             update_( buffer_ );
             m_ = 0;
 
             // clear buffered plaintext
             detail::memset( buffer_, 0, 8 );
         }
 
         BOOST_ASSERT( m_ == 0 );
 
         while( n >= 8 )
         {
             update_( p );
 
             p += 8;
             n -= 8;
         }
 
         BOOST_ASSERT( n < 8 );
 
         if( n > 0 )
         {
             detail::memcpy( buffer_, p, n );
             m_ = n;
         }
 
         BOOST_ASSERT( m_ == n_ % 8 );
     }
 
     void update( void const* pv, std::size_t n )
     {
         unsigned char const* p = static_cast<unsigned char const*>( pv );
         update( p, n );
     }
 
     BOOST_CXX14_CONSTEXPR std::uint64_t result()
     {
         BOOST_ASSERT( m_ == n_ % 8 );
 
         detail::memset( buffer_ + m_, 0, 8 - m_ );
 
         buffer_[ 7 ] = static_cast<unsigned char>( n_ & 0xFF );
 
         update_( buffer_ );
 
         v2 ^= 0xFF;
 
         sipround();
         sipround();
         sipround();
         sipround();
 
         n_ += 8 - m_;
         m_ = 0;
 
         // clear buffered plaintext
         detail::memset( buffer_, 0, 8 );
 
         return v0 ^ v1 ^ v2 ^ v3;
     }
 };
 
 class siphash_32
 {
 private:
 
     std::uint32_t v0 = 0;
     std::uint32_t v1 = 0;
     std::uint32_t v2 = 0x6c796765;
     std::uint32_t v3 = 0x74656462;
 
     unsigned char buffer_[ 4 ] = {};
     std::uint32_t m_ = 0; // == n_ % 4
 
     std::uint32_t n_ = 0;
 
 private:
 
     BOOST_CXX14_CONSTEXPR void sipround()
     {
         v0 += v1;
         v1 = detail::rotl(v1, 5);
         v1 ^= v0;
         v0 = detail::rotl(v0, 16);
         v2 += v3;
         v3 = detail::rotl(v3, 8);
         v3 ^= v2;
         v0 += v3;
         v3 = detail::rotl(v3, 7);
         v3 ^= v0;
         v2 += v1;
         v1 = detail::rotl(v1, 13);
         v1 ^= v2;
         v2 = detail::rotl(v2, 16);
     }
 
     BOOST_CXX14_CONSTEXPR void update_( unsigned char const * p )
     {
         std::uint32_t m = detail::read32le( p );
 
         v3 ^= m;
 
         sipround();
         sipround();
 
         v0 ^= m;
     }
 
 public:
 
     using result_type = std::uint32_t;
 
     siphash_32() = default;
 
     BOOST_CXX14_CONSTEXPR explicit siphash_32( std::uint64_t seed )
     {
         std::uint32_t k0 = static_cast<std::uint32_t>( seed );
         std::uint32_t k1 = static_cast<std::uint32_t>( seed >> 32 );
 
         v0 ^= k0;
         v1 ^= k1;
         v2 ^= k0;
         v3 ^= k1;
     }
 
     BOOST_CXX14_CONSTEXPR siphash_32( unsigned char const * p, std::size_t n )
     {
         if( n == 8 )
         {
             std::uint32_t k0 = detail::read32le( p + 0 );
             std::uint32_t k1 = detail::read32le( p + 4 );
 
             v0 ^= k0;
             v1 ^= k1;
             v2 ^= k0;
             v3 ^= k1;
         }
         else if( n != 0 )
         {
             update( p, n );
             result();
         }
     }
 
     siphash_32( void const * p, std::size_t n ): siphash_32( static_cast<unsigned char const*>( p ), n )
     {
     }
 
     BOOST_CXX14_CONSTEXPR void update( unsigned char const* p, std::size_t n )
     {
         BOOST_ASSERT( m_ == n_ % 4 );
 
         if( n == 0 ) return;
 
         n_ += static_cast<std::uint32_t>( n );
 
         if( m_ > 0 )
         {
             std::uint32_t k = 4 - m_;
 
             if( n < k )
             {
                 k = static_cast<std::uint32_t>( n );
             }
 
             detail::memcpy( buffer_ + m_, p, k );
 
             p += k;
             n -= k;
             m_ += k;
 
             if( m_ < 4 ) return;
 
             BOOST_ASSERT( m_ == 4 );
 
             update_( buffer_ );
             m_ = 0;
 
             // clear buffered plaintext
             detail::memset( buffer_, 0, 4 );
         }
 
         BOOST_ASSERT( m_ == 0 );
 
         while( n >= 4 )
         {
             update_( p );
 
             p += 4;
             n -= 4;
         }
 
         BOOST_ASSERT( n < 4 );
 
         if( n > 0 )
         {
             detail::memcpy( buffer_, p, n );
             m_ = static_cast<std::uint32_t>( n );
         }
 
         BOOST_ASSERT( m_ == n_ % 4 );
     }
 
     void update( void const* pv, std::size_t n )
     {
         unsigned char const* p = static_cast<unsigned char const*>( pv );
         update( p, n );
     }
 
     BOOST_CXX14_CONSTEXPR std::uint32_t result()
     {
         BOOST_ASSERT( m_ == n_ % 4 );
 
         detail::memset( buffer_ + m_, 0, 4 - m_ );
 
         buffer_[ 3 ] = static_cast<unsigned char>( n_ & 0xFF );
 
         update_( buffer_ );
 
         v2 ^= 0xFF;
 
         sipround();
         sipround();
         sipround();
         sipround();
 
         n_ += 4 - m_;
         m_ = 0;
 
         // clear buffered plaintext
         detail::memset( buffer_, 0, 4 );
 
         return v1 ^ v3;
     }
 };
 
 } // namespace hash2
 } // namespace boost
 
 #endif // #ifndef BOOST_HASH2_SIPHASH_HPP_INCLUDED

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