public unsafe override SkipListNode GetNode(long nodeLocation)
{
var ptr = (byte *)_pointer.ToPointer() + nodeLocation;
var length = Unsafe.Read <int>(ptr);
var node = new SkipListNode(new Span <byte>(ptr, length), nodeLocation);
return(node);
}
public SimpleAllocator(long maxSize, byte maxHeight)
: base(maxHeight)
{
_maxSize = maxSize;
_buffer.Add(null);
var headNodeSize = SkipListNode.CalculateSizeNeeded(maxHeight, 0);
_headNodeLocation = AllocateNode(headNodeSize, out var memory);
_ = new SkipListNode(memory, _headNodeLocation, maxHeight, Array.Empty <byte>());
}
private SearchResult Search(ReadOnlySpan <byte> key, out SkipListNode node)
{
var currentNode = _allocator.HeadNode;
var level = (byte)(_allocator.CurrentHeight - 1);
while (true)
{
var nextNodeLocation = currentNode.GetTableLocation(level);
if (nextNodeLocation == 0)
{
if (level > 0)
{
level--;
continue;
}
else
{
node = default;
return(SearchResult.NotFound);
}
}
node = _allocator.GetNode(nextNodeLocation);
var compare = key.SequenceCompareTo(node.Key);
if (compare == 0)
{
if (node.IsDeleted)
{
return(SearchResult.Deleted);
}
else
{
return(SearchResult.Found);
}
}
else if (compare > 0)
{
currentNode = node;
continue;
}
if (level > 0)
{
level--;
continue;
}
return(SearchResult.NotFound);
}
}
public SkipListNode AllocateNode(ReadOnlySpan <byte> key)
{
var height = _heightGenerator.GetHeight();
var memoryNeeded = SkipListNode.CalculateSizeNeeded(height, key.Length);
var nodeLocation = AllocateNode(memoryNeeded, out var memory);
if (nodeLocation == 0)
{
return(new SkipListNode());
}
var returnValue = new SkipListNode(memory, nodeLocation, height, key);
return(returnValue);
}
public NativeAllocator(long maxSize, byte maxHeight)
: base(maxHeight)
{
_maxSize = maxSize;
_pointer = VirtualAlloc(IntPtr.Zero, (UIntPtr)maxSize, AllocationType.MEM_COMMIT | AllocationType.MEM_RESERVE, Protection.PAGE_READWRITE);
if (_pointer == IntPtr.Zero)
{
var error = Marshal.GetLastWin32Error();
throw new OutOfMemoryException($"We could not allocate memory for the skip list error code was {error}");
}
_currentPointer = ALIGNMENTSIZE;
var headNodeSize = SkipListNode.CalculateSizeNeeded(maxHeight, 0);
AllocateNode(headNodeSize, out var memory);
_ = new SkipListNode(memory, ALIGNMENTSIZE, maxHeight, Array.Empty <byte>());
}
