Hash.H

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/*---------------------------------------------------------------------------*\
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-------------------------------------------------------------------------------
    Copyright (C) 2011-2012 OpenFOAM Foundation
    Copyright (C) 2018-2021 OpenCFD Ltd.
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    OpenFOAM 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 OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
Class
    Foam::Hash
 
Description
    Hash function class.
    The default definition is for primitives.
    Non-primitives used to hash entries on hash tables will need
    a specialized version.
 
\*---------------------------------------------------------------------------*/
 
#ifndef Hash_H
#define Hash_H
 
#include "Hasher.H"
#include <cstdint>
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                            Class Hash Declaration
\*---------------------------------------------------------------------------*/
 
template<class T>
struct Hash
{
    unsigned operator()(const T& obj, unsigned seed=0) const
    {
        return Foam::Hasher(&obj, sizeof(T), seed);
    }
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
//- Hashing of nullptr, always 0
template<>
struct Hash<std::nullptr_t>
{
    unsigned operator()(std::nullptr_t, unsigned seed=0) const noexcept
    {
        return seed;
    }
};
 
//- Hashing of pointers, treat as unsigned integer
template<>
struct Hash<void*>
{
    unsigned operator()(const void* const ptr, unsigned seed=0) const
    {
        const uintptr_t addr = uintptr_t(ptr);
        return Foam::Hasher(&addr, sizeof(addr), seed);
    }
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
// Specialization for common integral types
 
#undef  FOAM_HASH_SPECIALIZATION
#define FOAM_HASH_SPECIALIZATION(Type)                                        \
                                                                              \
                              \
  \
    template<>                                                                \
    struct Hash<Type>                                                         \
    {                                                                         \
        unsigned operator()(const Type val) const                             \
        {                                                                     \
            return static_cast<unsigned>(val);                                \
        }                                                                     \
        unsigned operator()(const Type val, unsigned seed) const              \
        {                                                                     \
            return Foam::Hasher(&val, sizeof(Type), seed);                    \
        }                                                                     \
    }
 
FOAM_HASH_SPECIALIZATION(bool);
FOAM_HASH_SPECIALIZATION(char);
FOAM_HASH_SPECIALIZATION(int32_t);
FOAM_HASH_SPECIALIZATION(int64_t);
FOAM_HASH_SPECIALIZATION(uint32_t);
#undef FOAM_HASH_SPECIALIZATION
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //