ryujinx/Ryujinx.HLE/Memory/ArenaAllocator.cs

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using System.Collections.Generic;
namespace Ryujinx.HLE.Memory
{
class ArenaAllocator
{
private class Region
{
public long Position { get; set; }
public long Size { get; set; }
public Region(long Position, long Size)
{
this.Position = Position;
this.Size = Size;
}
}
private LinkedList<Region> FreeRegions;
public long TotalAvailableSize { get; private set; }
public long TotalUsedSize { get; private set; }
public ArenaAllocator(long ArenaSize)
{
TotalAvailableSize = ArenaSize;
FreeRegions = new LinkedList<Region>();
FreeRegions.AddFirst(new Region(0, ArenaSize));
}
public bool TryAllocate(long Size, out long Position)
{
LinkedListNode<Region> Node = FreeRegions.First;
while (Node != null)
{
Region Rg = Node.Value;
if ((ulong)Rg.Size >= (ulong)Size)
{
Position = Rg.Position;
Rg.Position += Size;
Rg.Size -= Size;
TotalUsedSize += Size;
return true;
}
Node = Node.Next;
}
Position = 0;
return false;
}
public void Free(long Position, long Size)
{
long End = Position + Size;
Region NewRg = new Region(Position, Size);
LinkedListNode<Region> Node = FreeRegions.First;
LinkedListNode<Region> PrevSz = Node;
while (Node != null)
{
LinkedListNode<Region> NextNode = Node.Next;
Region Rg = Node.Value;
long RgEnd = Rg.Position + Rg.Size;
if (Rg.Position == End)
{
NewRg.Size += Rg.Size;
FreeRegions.Remove(Node);
}
else if (RgEnd == Position)
{
NewRg.Position = Rg.Position;
NewRg.Size += Rg.Size;
FreeRegions.Remove(Node);
}
else if ((ulong)Rg.Size < (ulong)NewRg.Size &&
(ulong)Rg.Size > (ulong)PrevSz.Value.Size)
{
PrevSz = Node;
}
Node = NextNode;
}
if ((ulong)PrevSz.Value.Size < (ulong)Size)
{
FreeRegions.AddAfter(PrevSz, NewRg);
}
else
{
FreeRegions.AddFirst(NewRg);
}
TotalUsedSize -= Size;
}
}
}