HashTableCore.H

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/*---------------------------------------------------------------------------*\
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    Copyright (C) 2011-2016 OpenFOAM Foundation
    Copyright (C) 2017-2025 OpenCFD Ltd.
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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
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    You should have received a copy of the GNU General Public License
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Class
    Foam::HashTableCore
 
Description
    Template invariant parts of hash table implementation.
 
SourceFiles
    HashTableCore.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef Foam_HashTableCore_H
#define Foam_HashTableCore_H
 
#include "label.H"
#include "className.H"
#include "nullObject.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                        Class HashTableCore Declaration
\*---------------------------------------------------------------------------*/
 
//- Bits that are independent of HashTable template parameters.
struct HashTableCore
{
    //- Maximum allowable internal table size (must be a power of two!).
    // - approximately (INT32_MAX/4) => 0x20000000
    // - don't need an int64 version
    static constexpr int32_t maxTableSize = (1 << (32-3));
 
    //- Return a canonical (power-of-two) of the requested size.
    static label canonicalSize(const label size) noexcept;
 
    //- Declare type-name (with debug switch)
    ClassName("HashTable");
 
    //- Default construct
    constexpr HashTableCore() noexcept = default;
 
    static_assert
    (
        sizeof(NullObject) >= sizeof(void*),
        "NullObject is too small to reinterpret_cast as HashTable::iterator"
    );
 
 
    //- Factory class for creating a begin/end pair for any const iterator
    //- type, normally associated with a HashTable.
    //  Uses begin iterator and size for bookkeeping.
    template<class IteratorType, class TableType>
    class const_iterator_pair
    {
        const label size_;
        IteratorType iter_;
 
    public:
 
        //- Default construct an empty pair
        const_iterator_pair()
        :
            size_(0),
            iter_()
        {}
 
        //- Construct begin/end pair for table
        const_iterator_pair(const TableType& tbl)
        :
            size_(tbl.size()),
            iter_(tbl.begin())
        {}
 
        bool empty() const noexcept { return !size_; }
        label size() const noexcept { return size_; }
 
        IteratorType begin() const noexcept { return iter_; }
        IteratorType cbegin() const noexcept { return iter_; }
 
        IteratorType end() const { return IteratorType(); }
        IteratorType cend() const { return IteratorType(); }
    };
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //