FixedList.H

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/*---------------------------------------------------------------------------*\
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   \\    /   O peration     |
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-------------------------------------------------------------------------------
    Copyright (C) 2011-2016 OpenFOAM Foundation
    Copyright (C) 2017-2026 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::FixedList

Description
    A 1D vector of objects of type <T> with a fixed length <N>.

SourceFiles
    FixedList.txx
    FixedListI.H
    FixedListIO.txx

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

#ifndef Foam_FixedList_H
#define Foam_FixedList_H

#include "bool.H"
#include "label.H"
#include "uLabel.H"
#include "zero.H"
#include "stdFoam.H"
#include "nullObject.H"
#include "Hash.H"
#include "ListPolicy.H"  // Also includes "contiguous"
#include "autoPtr.H"

#include <cstddef>
#include <limits>
#include <tuple>
#include <utility>

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

namespace Foam
{

// Forward Declarations

template<class T, unsigned N> class FixedList;
template<class T> class UList;

template<class T, unsigned N>
Istream& operator>>(Istream& is, FixedList<T, N>& list);

template<class T, unsigned N>
Ostream& operator<<(Ostream& os, const FixedList<T, N>& list);


/*---------------------------------------------------------------------------*\
                           Class FixedList Declaration
\*---------------------------------------------------------------------------*/

template<class T, unsigned N>
class FixedList
{
    static_assert
    (
        N && N <= std::numeric_limits<int>::max(),
        "Size must be positive (non-zero) and fit as a signed int value"
    );

    // Private Data

        //- Vector of values of type T of length N.
        T v_[N];


protected:

    // Protected Member Functions

        //- Write the FixedList with its compound type
        void writeEntry(Ostream& os) const;


public:

    // STL Type Definitions

        //- The value type the FixedList contains
        typedef T value_type;

        //- The pointer type for non-const access to value_type items
        typedef T* pointer;

        //- The pointer type for const access to value_type items
        typedef const T* const_pointer;

        //- The type used for storing into value_type objects
        typedef T& reference;

        //- The type used for reading from constant value_type objects.
        typedef const T& const_reference;

        //- Random access iterator for traversing FixedList
        typedef T* iterator;

        //- Random access iterator for traversing FixedList
        typedef const T* const_iterator;

        //- The type to represent the size of a FixedList
        typedef label size_type;

        //- The difference between iterator objects
        typedef label difference_type;

        //- Reverse iterator (non-const access)
        typedef std::reverse_iterator<iterator> reverse_iterator;

        //- Reverse iterator (const access)
        typedef std::reverse_iterator<const_iterator> const_reverse_iterator;


    // Static Functions

        //- Return a null FixedList (reference to a nullObject).
        //- Read/write access is questionable
        static const FixedList<T, N>& null() noexcept
        {
            return NullObjectRef<FixedList<T, N>>();
        }


    // Generated Methods

        //- Default construct
        FixedList() = default;

        //- Copy construct
        FixedList(const FixedList&) = default;

        //- Move construct
        FixedList(FixedList&&) = default;


    // Constructors

        //- Construct and initialize all entries to given value
        inline explicit FixedList(const T& val);

        //- Construct and initialize all entries to zero
        inline explicit FixedList(Foam::zero);

        //- Construct from an initializer list. Runtime size check
        inline FixedList(std::initializer_list<T> list);

        //- Construct from UList. Runtime size check
        inline explicit FixedList(const UList<T>& list);

        //- Copy construct from a subset of the input. No size check
        template<unsigned AnyNum>
        inline FixedList
        (
            const FixedList<T, AnyNum>& list,
            const FixedList<label, N>& indices
        );

        //- Copy construct from a subset of the input. No size check
        inline FixedList
        (
            const UList<T>& list,
            const FixedList<label, N>& indices
        );

        //- Construct from Istream
        explicit FixedList(Istream& is);

        //- Clone
        inline autoPtr<FixedList<T, N>> clone() const;


    // Member Functions

    // Access

        //- Return pointer to the underlying array serving as data storage.
        inline constexpr const T* cdata() const noexcept;

        //- Return pointer to the underlying array serving as data storage.
        inline constexpr T* data() noexcept;

        //- Return pointer to the underlying array serving as data storage,
        //  reinterpreted as byte data
        //  \note Only meaningful for contiguous data
        inline constexpr const char* cdata_bytes() const noexcept;

        //- Return pointer to the underlying array serving as data storage,
        //  reinterpreted as byte data
        //  \note Only meaningful for contiguous data
        inline constexpr char* data_bytes() noexcept;

        //- Number of contiguous bytes for the list data,
        //  \note Only meaningful for contiguous data
        inline static std::streamsize size_bytes() noexcept;

        //- Number of contiguous bytes for the list data,
        //- runtime FatalError if type is not contiguous
        static std::streamsize byteSize();

        //- Element access using compile-time indexing
        template<unsigned I>
        inline constexpr T& get() noexcept;

        //- Element access using compile-time indexing
        template<unsigned I>
        inline constexpr const T& get() const noexcept;

        //- Access first element of the list, position [0]
        inline constexpr T& front() noexcept;

        //- Access first element of the list, position [0]
        inline constexpr const T& front() const noexcept;

        //- Access last element of the list, position [N-1]
        inline constexpr T& back() noexcept;

        //- Access last element of the list, position [N-1]
        inline constexpr const T& back() const noexcept;

        //- Return the forward circular index, i.e. next index
        //- which returns to the first at the end of the list
        inline constexpr label fcIndex(label i) const noexcept;

        //- Return forward circular value (ie, next value in the list)
        inline const T& fcValue(label i) const;

        //- Return forward circular value (ie, next value in the list)
        inline T& fcValue(label i);

        //- Return the reverse circular index, i.e. previous index
        //- which returns to the last at the beginning of the list
        inline constexpr label rcIndex(label i) const noexcept;

        //- Return reverse circular value (ie, previous value in the list)
        inline const T& rcValue(label i) const;

        //- Return reverse circular value (ie, previous value in the list)
        inline T& rcValue(label i);


    // Check

        //- Check start is within valid range [0,size)
        inline void checkStart(const label start) const;

        //- Check size is identical to template parameter N
        inline void checkSize(const label size) const;

        //- Check index is within valid range [0,N)
        inline void checkIndex(const label i) const;

        //- True if all entries have identical values, and list is non-empty
        inline bool uniform() const;


    // Search

        //- True if the value is contained in the list.
        inline bool contains(const T& val) const;

        //- Is the value contained in the list?
        //  \param val The value to search for
        //  \param pos The first position to examine (no-op if -ve)
        //  \param len The length of the search region (-ve until the end)
        //  \return true if found.
        inline bool contains(const T& val, label pos, label len = -1) const;

        //- Find index of the first occurrence of the value.
        //  \param val The value to search for
        //  \return position in list or -1 if not found.
        label find(const T& val) const;

        //- Find index of the first occurrence of the value.
        //  \param val The value to search for
        //  \param pos The first position to examine (no-op if -ve)
        //  \param len The length of the search region (-ve until the end)
        //  \return position in list or -1 if not found.
        label find(const T& val, label pos, label len = -1) const;

        //- Find index of the last occurrence of the value.
        //  Any occurrences after the end pos are ignored.
        //  Linear search.
        //  \return position in list or -1 if not found.
        label rfind(const T& val, label pos = -1) const;


    // Edit

        //- Dummy function, to make FixedList consistent with List
        //- Any resizing is ignored (Fatal with bad sizing in full debug).
        inline void resize(const label n);

        //- Set val for \em all elements.
        //- Any resizing is ignored (Fatal with bad sizing in full debug).
        inline void resize_fill(const label n, const T& val);

        //- Dummy function, to make FixedList consistent with List
        //- Any resizing is ignored (Fatal with bad sizing in full debug).
        inline void resize_nocopy(const label n);

        //- Dummy function, to make FixedList consistent with List
        void setSize(const label n) { this->resize(n); }

        //- Assign all entries to the given value
        inline void fill(const T& val);

        //- Assign all entries to zero
        inline void fill(Foam::zero);

        //- Move element to the first position.
        void moveFirst(const label i);

        //- Move element to the last position.
        void moveLast(const label i);

        //- Swap element with the first element.
        void swapFirst(const label i);

        //- Swap element with the last element.
        void swapLast(const label i);

        //- Transfer by swapping using a move assignment for the content
        //- of the individual list elements
        inline void transfer(FixedList<T, N>& list);


    // Member Operators

        //- Return element of FixedList
        inline T& operator[](const label i);

        //- Return element of constant FixedList
        inline const T& operator[](const label i) const;

        //- Assignment to UList operator. Takes linear time
        inline void operator=(const UList<T>& list);

        //- Assignment to an initializer list. Takes linear time
        inline void operator=(std::initializer_list<T> list);

        //- Assign all entries to the given value. fill()
        inline void operator=(const T& val);

        //- Assign all entries to zero. fill()
        inline void operator=(Foam::zero);

        //- Copy assignment
        inline void operator=(const FixedList& list);

        //- Move assignment
        inline void operator=(FixedList&& list);


    // Random access iterator (non-const)

        //- Return an iterator to begin traversing the FixedList
        inline iterator begin() noexcept;

        //- Return an iterator to end traversing the FixedList
        inline iterator end() noexcept;

        //- Return iterator at offset i from begin,
        //- clamped to [0,N] range
        inline iterator begin(const int i) noexcept;


    // Random access iterator (const)

        //- Return const_iterator to begin traversing the constant FixedList
        inline const_iterator cbegin() const noexcept;

        //- Return const_iterator to end traversing the constant FixedList
        inline const_iterator cend() const noexcept;

        //- Return const_iterator to begin traversing the constant FixedList
        inline const_iterator begin() const noexcept;

        //- Return const_iterator to end traversing the constant FixedList
        inline const_iterator end() const noexcept;

        //- Return const_iterator at offset i from begin,
        //- clamped to [0,N] range
        inline const_iterator cbegin(const int i) const noexcept;

        //- Return const_iterator at offset i from begin,
        //- clamped to [0,N] range
        inline const_iterator begin(const int i) const noexcept;


    // Reverse iterator (non-const)

        //- Return reverse_iterator to begin reverse traversing the FixedList
        inline reverse_iterator rbegin();

        //- Return reverse_iterator to end reverse traversing the FixedList
        inline reverse_iterator rend();


    // Reverse iterator (const)

        //- Return const_reverse_iterator to begin reverse traversing FixedList
        inline const_reverse_iterator crbegin() const;

        //- Return const_reverse_iterator to end reverse traversing FixedList
        inline const_reverse_iterator crend() const;

        //- Return const_reverse_iterator to begin reverse traversing FixedList
        inline const_reverse_iterator rbegin() const;

        //- Return const_reverse_iterator to end reverse traversing FixedList
        inline const_reverse_iterator rend() const;


    // STL Member Functions

        //- Always false since zero-sized FixedList is compile-time disabled.
        static constexpr bool empty() noexcept { return !N; }

        //- Return the number of elements in the FixedList
        static constexpr label size() noexcept { return N; }

        //- The dimensioned size (template parameter N) of the FixedList
        static constexpr unsigned max_size() noexcept { return N; }

        //- Swap lists by swapping the content of the individual list elements
        //  Essentially std::swap_ranges
        inline void swap(FixedList<T, N>& other);


    // STL Member Operators

        //- Equality operation on FixedLists of the same type.
        //  Returns true when the FixedLists are element-wise equal
        //  (using FixedList::value_type::operator==). Takes linear time
        bool operator==(const FixedList& other) const;

        //- Compare two FixedLists lexicographically. Takes linear time
        bool operator<(const FixedList& other) const;

        //- The opposite of the equality operation. Takes linear time
        bool operator!=(const FixedList& other) const
        {
            return !(*this == other);
        }

        //- Return true if !(a > b). Takes linear time
        bool operator<=(const FixedList& other) const
        {
            return !(other < *this);
        }

        //- Compare two FixedLists lexicographically. Takes linear time
        bool operator>(const FixedList& other) const
        {
            return (other < *this);
        }

        //- Return true if !(a < b). Takes linear time
        bool operator>=(const FixedList& other) const
        {
            return !(*this < other);
        }


    // Reading/writing

        //- Read from Istream, discarding contents of existing List
        Istream& readList(Istream& is);

        //- Write the list as a dictionary entry with keyword
        void writeEntry(const word& keyword, Ostream& os) const;

        //- Write List, with line-breaks in ASCII when length exceeds shortLen.
        //  Using '0' suppresses line-breaks entirely.
        Ostream& writeList(Ostream& os, const label shortLen=0) const;


    // IOstream Operators

        //- Use the readList() method to read contents from Istream.
        friend Istream& operator>> <T, N>
        (
            Istream& is,
            FixedList<T, N>& list
        );


    // Hashing

        //- Hashing functor for FixedList.
        struct hasher
        {
            inline unsigned operator()
            (
                const FixedList<T, N>& obj,
                unsigned seed=0
            ) const
            {
                if constexpr (is_contiguous_v<T>)
                {
                    return Foam::Hasher(obj.cdata(), obj.size_bytes(), seed);
                }
                else
                {
                    Foam::Hash<T> op;
                    for (const T& val : obj)
                    {
                        seed = op(val, seed);
                    }
                    return seed;
                }
            }
        };

        //- Deprecated(2021-04) hashing functor. Use hasher()
        // \deprecated(2021-04) - use hasher() functor
        template<class Unused=bool>
        struct Hash : FixedList<T, N>::hasher
        {
            FOAM_DEPRECATED_FOR(2021-04, "hasher()") Hash() {}
        };


    // Housekeeping

        //- Access first element of the list, position [0] - front()
        T& first() noexcept { return front(); }

        //- Access first element of the list, position [0] - front()
        const T& first() const noexcept { return front(); }

        //- Access last element of the list, position [N-1] - back()
        T& last() noexcept { return back(); }

        //- Access last element of the list, position [N-1] - back()
        const T& last() const noexcept { return back(); }

        //- Same as contains()
        bool found(const T& val, label pos = 0) const
        {
            return this->contains(val, pos);
        }


        //- Deprecated: copy construct from C-array
        explicit FixedList(const T list[N]) { std::copy_n(list, N, v_); }

        //- Deprecated: assignment from C-array
        // \deprecated(2023-08) - use other assignment operators
        void operator=(const T list[N]) { std::copy_n(list, N, v_); }
};


// * * * * * * * * * * * * * * * * * Traits  * * * * * * * * * * * * * * * * //

//- FixedList is contiguous if the type is contiguous
template<class T, unsigned N>
struct is_contiguous<FixedList<T, N>> : is_contiguous<T> {};

//- Check for FixedList of labels
template<class T, unsigned N>
struct is_contiguous_label<FixedList<T, N>> : is_contiguous_label<T> {};

//- Check for FixedList of scalars
template<class T, unsigned N>
struct is_contiguous_scalar<FixedList<T, N>> : is_contiguous_scalar<T> {};

//- Hashing for FixedList data
template<class T, unsigned N>
struct Hash<FixedList<T, N>> : FixedList<T, N>::hasher {};

//- Test if FixedList is the base class
template<class T>
inline constexpr bool is_fixedlist_v
    = stdFoam::is_template_nttp_base_of_v<Foam::FixedList, T>;


// * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //

//- Read List contents from Istream, list must have the proper size!
template<class T, unsigned N>
Istream& operator>>(Istream& is, FixedList<T, N>& list)
{
    return list.readList(is);
}


//- Write List to Ostream, as per FixedList::writeList() with default length.
//  The default short-length is given by Foam::ListPolicy::short_length
template<class T, unsigned N>
Ostream& operator<<(Ostream& os, const FixedList<T, N>& list)
{
    return list.writeList(os, Foam::ListPolicy::short_length<T>::value);
}


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

} // End namespace Foam

// * * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * //

namespace Foam
{

//- Swap FixedList contents - see FixedList::swap().
//  Essentially std::swap_ranges
template<class T, unsigned N>
inline void Swap(FixedList<T, N>& a, FixedList<T, N>& b)
{
    a.swap(b);
}


// * * * * * * * * * * * * * * * ADL Lookups * * * * * * * * * * * * * * * * //

template<std::size_t I, class T, unsigned N>
constexpr T& get(FixedList<T, N>& list) noexcept
{
    static_assert(I < N, "FixedList index out-of-range");
    return *(list.data() + I);
}

template<std::size_t I, class T, unsigned N>
constexpr const T& get(const FixedList<T, N>& list) noexcept
{
    static_assert(I < N, "FixedList index out-of-range");
    return *(list.cdata() + I);
}

template<std::size_t I, class T, unsigned N>
constexpr T&& get(FixedList<T, N>&& list) noexcept
{
    static_assert(I < N, "FixedList index out-of-range");
    return std::move(*(list.data() + I));
}

template<std::size_t I, class T, unsigned N>
constexpr const T&& get(const FixedList<T, N>&& list) noexcept
{
    static_assert(I < N, "FixedList index out-of-range");
    return std::move(*(list.cdata() + I));
}

} // End namespace Foam


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

// Specializations (structured binding)
namespace std
{

//- The tuple_size of FixedList is (N)
template<class T, unsigned N>
struct tuple_size<Foam::FixedList<T, N>>
: std::integral_constant<std::size_t, N> {};

//- Identical type for all elements of FixedList
template<std::size_t I, class T, unsigned N>
struct tuple_element<I, Foam::FixedList<T, N>> { using type = T; };

} // End namespace std


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

#include "FixedListI.H"

// * * * * * * * * * * * * * * * Implementations * * * * * * * * * * * * * * //

// FUTURE?
// template<class T, unsigned N>
// constexpr Foam::UList<T>::UList(const FixedList<T>& list) noexcept
// :
//     UList<T>(const_cast<T*>(list.cdata()), list.size())
// {}


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

#ifdef NoRepository
    #include "FixedList.txx"
    #include "FixedListIO.txx"
#endif

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

#endif

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