fixedcapacityvector.hpp

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//==================================================================================================
/// \file
/// This header file is part of module \alib_containers of the \aliblong.
///
/// \emoji :copyright: 2013-2024 A-Worx GmbH, Germany.
/// Published under \ref mainpage_license "Boost Software License".
//==================================================================================================
#ifndef HPP_ALIB_MONOMEM_CONTAINERS_FIXED_CAPACITY_VECTOR
#define HPP_ALIB_MONOMEM_CONTAINERS_FIXED_CAPACITY_VECTOR
#pragma once
#if !defined(DOXYGEN)
#   include "alib/alib.hpp"
#endif
ALIB_ASSERT_MODULE(CONTAINERS)
#include <array>
#include <queue>
 
namespace alib {  namespace containers {
 
//==================================================================================================
/// This class fills the gap between standard types <c>std::array</c> and <c>std::vector</c> by
/// implementing a fixed size array, with a current filling size index.
/// With that methods #push_back and #pop_back could be implemented, which satisfies the constraints
/// given for example to underlying containers of type <c>std::priority_queue</c>.
///
/// The rationale here is to use fixed size memory allocation or even stack allocation, in situations
/// where the maximum capacity needed at runtime is known upfront.
///
/// Besides aforementioned methods \c push_back and \c pop_back, a few necessary other methods
/// of parent class <c>std::array</c> have been replaced, but are not explicitly mentioned with
/// this reference documentation. Among them are \c size(), \c end(), \c rend() or \c cend().
///
/// \attention
///   While this type inherits <c>std::array</c> publicly, not all standard methods and type
///   traits have been overwritten according to the ever more complicated C++ specification.
///   Therefore, there is not only no guarantee given that this type behaves as it is supposed to in
///   each and every complex situation (e.g template meta programing).
///   However, the use in accordance with type \c std::priority_queue is certified.
///
/// @tparam T     The type to store.
/// @tparam TSize The fixed sitze of the vector.
//==================================================================================================
template<typename T, std::size_t TSize>
class FixedCapacityVector : public std::array<T, TSize>
{
    protected:
        std::size_t fillSize= 0;       ///< The current fill
 
    public:
       /// Increases the size of this vector by inserting given \p value at the end.<br>
       /// In debug compilations, an \alib assertion is raised, if this fixed sized vector's
       /// capacity is exceeded.
       /// @param value The value to insert.
        void push_back( const T& value )
        {
            ALIB_ASSERT_ERROR( fillSize < TSize, "MONOMEM/UT", "FixedCapacityVector overflow: ",
                                                              int(fillSize) )
            (*this)[fillSize++]= value;
        }
 
       /// Decreases the size of this vector by destructing and removing the given \p value at the
       /// current end.<br>
       /// In debug compilations, an \alib assertion is raised, if no elements are left.
        void pop_back()
        {
            ALIB_ASSERT_ERROR( fillSize > 0   , "MONOMEM/UT", "FixedCapacityVector underflow: ",
                                                              int(fillSize) )
            (*this)[--fillSize].~T();
        }
 
#if !DOXYGEN
    ALIB_WARNINGS_ALLOW_UNSAFE_BUFFER_USAGE
        [[nodiscard]]
        typename std::array<T, TSize>::size_type
        size() const
        { return fillSize; }
 
        [[nodiscard]]
        constexpr typename std::array<T, TSize>::iterator                   end()           noexcept
        { return std::array<T, TSize>::begin() + fillSize; }
 
        [[nodiscard]]
        constexpr typename std::array<T, TSize>::const_iterator             end()   const   noexcept
        { return std::array<T, TSize>::begin() + fillSize; }
 
        [[nodiscard]]
        constexpr
        typename std::array<T, TSize>::const_iterator                       cend()          noexcept
        { return std::array<T, TSize>::cbegin() + fillSize; }
 
        [[nodiscard]]
        constexpr
        typename std::array<T, TSize>::const_iterator                       cend()  const   noexcept
        { return std::array<T, TSize>::cbegin() + fillSize; }
    ALIB_WARNINGS_RESTORE
#endif // !DOXYGEN
 
}; // FixedCapacityVector
 
/// Type alias which denotes a <c>std::priority_queue</c> using
/// a \alib{containers;FixedCapacityVector} as its underlying container type.
template<typename T, std::size_t TSize, typename TCompare= std::less<T>>
using FixedSizePriorityQueue = std::priority_queue< T, FixedCapacityVector<T, TSize>, TCompare>;
 
} // namespace alib[::containers]
 
 
/// Type alias in namespace \b alib.
template<typename T, std::size_t TSize>
using     FixedCapacityVector  =   containers::FixedCapacityVector<T, TSize>;
 
 
/// Type alias in namespace \b alib, which denotes a <c>std::priority_queue</c> using
/// a \alib{containers;FixedCapacityVector} as its underlying container type.
template<typename T, std::size_t TSize, typename TCompare= std::less<T>>
using FixedSizePriorityQueue = std::priority_queue< T, FixedCapacityVector<T, TSize>, TCompare>;
 
} // namespace [alib]
 
 
 
#endif // HPP_ALIB_MONOMEM_CONTAINERS_FIXED_CAPACITY_VECTOR