stringOpsSort.H

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/*---------------------------------------------------------------------------*\
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    Copyright (C) 2017-2025 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.

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InNamespace
    Foam::stringOps

Description
    Specialized string sorting.

SourceFiles
    stringOpsSort.cxx

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

#ifndef Foam_stringOpsSort_H
#define Foam_stringOpsSort_H

#include "stringOps.H"

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

namespace Foam
{
namespace stringOps
{

//- 'Natural' compare for C-strings
//  Uses algorithm and code from Jan-Marten Spit <[email protected]>
//
//  In the 'natural' comparison, strings are compared alphabetically
//  and numerically. Thus 'file010.txt' sorts after 'file2.txt'
//
//  \param s1 left string
//  \param s2 right string
//  \return -1 when s1 < s2, 0 when s1 == s2, 1 when s1 > s2
int natstrcmp(const char* s1, const char* s2);


//- Encapsulation of natural order sorting for algorithms
struct natural_sort
{
    //- Natural compare for std::string
    //  \return -1 when s1 < s2, 0 when s1 == s2, 1 when s1 > s2
    static inline int compare
    (
        const std::string& s1,
        const std::string& s2
    )
    {
        return stringOps::natstrcmp(s1.data(), s2.data());
    }

    //- Natural compare two strings for a less-than relationship
    static inline bool less
    (
        const std::string& s1,
        const std::string& s2
    )
    {
        return (natural_sort::compare(s1, s2) < 0);
    }

    //- Natural compare two strings for a greater-than relationship
    static inline bool greater
    (
        const std::string& s1,
        const std::string& s2
    )
    {
        return (natural_sort::compare(s1, s2) > 0);
    }

    //- Default (forward) natural sorting
    bool operator()(const std::string& s1, const std::string& s2) const
    {
        return (natural_sort::compare(s1, s2) < 0);
    }

    //- Reverse natural sorting
    struct reverse
    {
        //- Reverse natural sorting
        bool operator()(const std::string& s1, const std::string& s2) const
        {
            return (natural_sort::compare(s1, s2) > 0);
        }
    };


    //- A UList compare binary predicate for natural sort
    template<class T>
    struct list_less
    {
        const UList<T>& values;

        list_less(const UList<T>& list) noexcept
        :
            values(list)
        {}

        bool operator()(label a, label b) const
        {
            return (natural_sort::compare(values[a], values[b]) < 0);
        }
    };


    //- A Ulist compare binary predicate for reverse natural sort
    template<class T>
    struct list_greater
    {
        const UList<T>& values;

        list_greater(const UList<T>& list) noexcept
        :
            values(list)
        {}

        bool operator()(label a, label b) const
        {
            return (natural_sort::compare(values[a], values[b]) > 0);
        }
    };
};


} // End namespace stringOps
} // End namespace Foam

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

#endif

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