Custom memory allocation in C# Part 8 — Unsafe list in .NET Core x64

This is the eighth part of the Custom memory allocation series. For your convenience you can find other parts in the table of contents in Part 1 — Allocating object on a stack

Today we are going to revisit an Unsafe list example using .NET Core. Since I use x64 edition, I need to adjust a code using pointers:

public void Add(T item)
{
	_currentIndex++;

	unsafe
	{
		TypedReference reference = __makeref(item);
		long* itemAddress = (long*) (*(long*) *(long*) &reference - 8);

		for (long i = 1; i < _elementSize; ++i)
		{
			_storage[_currentIndex*_elementSize + i] = *itemAddress;
			itemAddress = itemAddress + 1;
		}

		reference = __makeref(_storage);
		_storage[_currentIndex*_elementSize] = *(long*) *(long*) &reference + _currentIndex*_elementSize*8 + 32;
		_elements[_currentIndex] = GetInternal(_currentIndex);
	}
}

public void Add(T item)

{

_currentIndex++;

unsafe

{

TypedReference reference = __makeref(item);

long* itemAddress = (long*) (*(long*) *(long*) &reference - 8);

for (long i = 1; i < _elementSize; ++i)

{

_storage[_currentIndex*_elementSize + i] = *itemAddress;

itemAddress = itemAddress + 1;

}

reference = __makeref(_storage);

_storage[_currentIndex*_elementSize] = *(long*) *(long*) &reference + _currentIndex*_elementSize*8 + 32;

_elements[_currentIndex] = GetInternal(_currentIndex);

}

Changes are rather simple — one just needs to replace integers with longs and multiply all the offsets by two.

class Poco
{
	public long Field1;
	public long Field2;
	public long Field3;
	public long Field4;
	public long Field5;
	public long Field6;
	public long Field7;
	public long Field8;
	public long Field9;
	public long Field10;
	public long Field11;
	public long Field12;
	public long Field13;
	public long Field14;
	public long Field15;
	public long Field16;
}

class Poco

{

public long Field1;

public long Field2;

public long Field3;

public long Field4;

public long Field5;

public long Field6;

public long Field7;

public long Field8;

public long Field9;

public long Field10;

public long Field11;

public long Field12;

public long Field13;

public long Field14;

public long Field15;

public long Field16;

}

Here I just use long fields to make the code simpler. Of course one can detect the size of the object and work with integers as well.

Here are the results:

Results

Unsafe list is still faster.