Re: C++ Memory Management Innovation: GC Allocator

On Apr 22, 4:13 am, xushiwei <xushiwe...@gmail.com> wrote:


[ the rest skipped]

Had a look at your code... Looks unnecessarily complicated to me. Here
is the result of about 15 minutes of work:

[code]
#include <deque>
#include <cassert>

using namespace std;

struct FastAlloc
{
    struct Block
    {
        unsigned char memory[1024];
    };
    deque<Block> m_pool;
    size_t m_left;

    FastAlloc() : m_left(0) {}

    void* allocate(size_t size)
    {
        assert(size <= 1024);
        if (size > m_left)
        {
            m_pool.resize(m_pool.size() + 1);
            m_left = 1024;
        }

        void* res = m_pool.back().memory + 1024 - m_left;
        m_left -= size;
        return res;
    }
};

template<class T>
class my_alloc
{
public:
    FastAlloc* m_alloc;
typedef T value_type;

    typedef value_type* pointer;
typedef value_type& reference;
typedef value_type const* const_pointer;
typedef value_type const& const_reference;

    typedef std::size_t size_type;
    typedef std::ptrdiff_t difference_type;

template<class _Other>
struct rebind
{ // convert an my_alloc<_Ty> to an my_alloc <_Other>
typedef my_alloc<_Other> other;
};

pointer address(reference _Val) const
{ // return address of mutable _Val
return pointer(&_Val);
}

const_pointer address(const_reference _Val) const
{ // return address of nonmutable _Val
return const_pointer(&_Val);
}
/*
my_alloc()
{ // construct default my_alloc (do nothing)
}
        */

        my_alloc(FastAlloc& alloc) : m_alloc(&alloc)
{ // construct default my_alloc (do nothing)
}

my_alloc(const my_alloc<T>& o)
{ // construct by copying (do nothing)
            m_alloc = o.m_alloc;
}

template<class _Other>
my_alloc(const my_alloc<_Other>& o)
{ // construct from a related my_alloc (do nothing)
            m_alloc = o.m_alloc;
}

template<class _Other>
my_alloc<T>& operator=(const my_alloc<_Other>&)
{ // assign from a related my_alloc (do nothing)
            m_alloc = o.m_alloc;
     return (*this);
}

void deallocate(pointer _Ptr, size_type)
{ // deallocate object at _Ptr, ignore size
}

pointer allocate(size_type _Count, const void _FARQ * = 0)
{ // allocate array of _Count elements, ignore hint
            return pointer(m_alloc->allocate(_Count*sizeof(T)));
}

void construct(pointer _Ptr, T const& _Val)
{ // construct object at _Ptr with value _Val
new (_Ptr) T(_Val);
}

void destroy(pointer _Ptr)
{ // destroy object at _Ptr
(*_Ptr).~T();
}

    std::size_t max_size() const
{ // estimate maximum array size
std::size_t _Count = (std::size_t)(-1) / sizeof (T);
return (0 < _Count ? _Count : 1);
}
};

int main()
{
    FastAlloc alloc;

    deque<int, my_alloc<int> > q(alloc);

    q.push_back(1024);
    return 1;
}
[/code]

add STD_NEW/STD_DELETE support, parametrize my_alloc with allocator
type, write few different allocator classes and that's it. Looks much
more simple.

Sincerely yours,
Michael.

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