92 lines
2.6 KiB
C++
92 lines
2.6 KiB
C++
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//---------------------------------------------------------------------------//
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// Copyright (c) 2013-2014 Kyle Lutz <kyle.r.lutz@gmail.com>
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//
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// Distributed under the Boost Software License, Version 1.0
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// See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt
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//
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// See http://boostorg.github.com/compute for more information.
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//---------------------------------------------------------------------------//
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#ifndef BOOST_COMPUTE_FUNCTIONAL_HASH_HPP
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#define BOOST_COMPUTE_FUNCTIONAL_HASH_HPP
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#include <boost/compute/function.hpp>
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#include <boost/compute/types/fundamental.hpp>
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namespace boost {
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namespace compute {
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namespace detail {
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template<class Key>
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std::string make_hash_function_name()
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{
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return std::string("boost_hash_") + type_name<Key>();
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}
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template<class Key>
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inline std::string make_hash_function_source()
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{
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std::stringstream source;
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source << "inline ulong " << make_hash_function_name<Key>()
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<< "(const " << type_name<Key>() << " x)\n"
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<< "{\n"
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// note we reinterpret the argument as a 32-bit uint and
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// then promote it to a 64-bit ulong for the result type
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<< " ulong a = as_uint(x);\n"
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<< " a = (a ^ 61) ^ (a >> 16);\n"
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<< " a = a + (a << 3);\n"
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<< " a = a ^ (a >> 4);\n"
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<< " a = a * 0x27d4eb2d;\n"
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<< " a = a ^ (a >> 15);\n"
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<< " return a;\n"
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<< "}\n";
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return source.str();
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}
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template<class Key>
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struct hash_impl
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{
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typedef Key argument_type;
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typedef ulong_ result_type;
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hash_impl()
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: m_function("")
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{
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m_function = make_function_from_source<result_type(argument_type)>(
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make_hash_function_name<argument_type>(),
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make_hash_function_source<argument_type>()
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);
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}
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template<class Arg>
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invoked_function<result_type, boost::tuple<Arg> >
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operator()(const Arg &arg) const
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{
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return m_function(arg);
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}
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function<result_type(argument_type)> m_function;
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};
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} // end detail namespace
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/// The hash function returns a hash value for the input value.
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///
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/// The return type is \c ulong_ (the OpenCL unsigned long type).
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template<class Key> struct hash;
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/// \internal_
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template<> struct hash<int_> : detail::hash_impl<int_> { };
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/// \internal_
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template<> struct hash<uint_> : detail::hash_impl<uint_> { };
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/// \internal_
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template<> struct hash<float_> : detail::hash_impl<float_> { };
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} // end compute namespace
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} // end boost namespace
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#endif // BOOST_COMPUTE_FUNCTIONAL_HASH_HPP
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