/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2011 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
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 for primitives.  All non-primitives used to hash
    entries on hash tables likely need a specialized version of this class.

\*---------------------------------------------------------------------------*/

#ifndef Hash_H
#define Hash_H

#include "label.H"
#include "uLabel.H"
#include "Hasher.H"
#include "pTraits.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

namespace Foam
{
//template<class Type> class Hash;
//template<> class Hash<label>;

/*---------------------------------------------------------------------------*\
                            Class Hash Declaration
\*---------------------------------------------------------------------------*/

template<class PrimitiveType>
class Hash
{
public:

    Hash()
    {}

    unsigned operator()(const PrimitiveType& p, unsigned seed) const
    {
        return Hasher(&p, sizeof(p), seed);
    }

    unsigned operator()(const PrimitiveType& p) const
    {
        return Hasher(&p, sizeof(p));
    }

};


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

//- Hash specialization for hashing labels
template<>
class Hash<Foam::label>
{
public:

    Hash()
    {}

    //- Incrementally hash a label.
    //  This will necessarily return a different value than the
    //  non-incremental version.
    unsigned operator()(const label p, unsigned seed) const
    {
        return Hasher(&p, sizeof(label), seed);
    }

    //- Return the unsigned representation of a label.
    //  This helps if people have relied on the hash value corresponding to
    //  the natural order.
    unsigned operator()(const label p) const
    {
        return p;
    }
};


//- Hash specialization for hashing pointer addresses.
//  Treat a pointer like a long.
//  This should work for both 32-bit and 64-bit pointers.
template<>
class Hash<void*>
{
public:
   typedef intptr_t HashType;

    Hash()
    {}

    unsigned operator()(const void* const& p, unsigned seed) const
    {
        return Hash<HashType>()(HashType(p), seed);
    }

    unsigned operator()(const void* const& p) const
    {
        return Hash<HashType>()(HashType(p));
    }

};


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

} // End namespace Foam

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#endif

// ************************************************************************* //
