arena_allocator.h

// Description: Arena allocator
// Detail: A deallocate-once, arbitrary size memory allocator

#ifndef PASTELSYS_ARENA_ALLOCATOR_H
#define PASTELSYS_ARENA_ALLOCATOR_H

#include "pastel/sys/mytypes.h"

#include <list>

namespace Pastel
{

    //! A deallocate-once, arbitrary size memory allocator.

    class ArenaAllocator
    {
    public:
        //! Constructs with the given parameters.
        /*!
       Time complexity: constant
       Exception safety: strong
       */
        explicit ArenaAllocator(
            integer unitSize = 1,
            integer blockSize = 256);

        //! Destructs the allocators.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        ~ArenaAllocator();

        //! Swaps two allocators.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        void swap(ArenaAllocator& that);

        //! Deallocates all memory.
        /*!
       Time complexity: linear
       Exception safety: nothrow
       */
        void clear();

        //! Returns the unit size.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        integer unitSize() const;

        //! Returns the amount of units allocated this far.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        integer allocated() const;

        //! Returns the amount of units allocated internally.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        integer capacity() const;

        //! Allocates given number of units of memory.
        /*!
       Preconditions:
       units >= 0

       Time complexity: amortized constant
       Exception safety: nothrow

       If 'units' is zero a null pointer is
       returned.
       */
        void* allocate(integer units = 1);

        //! Deallocates given number of units of memory
        /*
       Time complexity: constant
       Exception safety: nothrow
       */
        void deallocate(const void* memoryIgnored, integer units = 1);

    private:
        ArenaAllocator(const ArenaAllocator& that) = delete;
        ArenaAllocator& operator=(const ArenaAllocator& that) = delete;

        struct Block
        {
            uint8* data_;
            integer unitsAllocated_;
            integer unitsReserved_;
        };

        using Container = std::list<Block>;
        using Iterator = Container::iterator;
        using ConstIterator = Container::const_iterator;

        void allocateBlock(integer minUnits);
        void deallocateBlock(Block* block);

        Container blocks_;
        integer unitsAllocated_;
        integer unitsReserved_;
        integer unitSize_;
        integer blockSize_;
    };

    void swap(ArenaAllocator& left, ArenaAllocator& right);

}

#include "pastel/sys/allocator/arena_allocator/arena_allocator.hpp"

#endif