R/ARMeilleure/Translation/Cache/CacheMemoryAllocator.cs

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using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
namespace ARMeilleure.Translation.Cache
{
class CacheMemoryAllocator
{
private struct MemoryBlock : IComparable<MemoryBlock>
{
public int Offset { get; }
public int Size { get; }
public MemoryBlock(int offset, int size)
{
Offset = offset;
Size = size;
}
public int CompareTo([AllowNull] MemoryBlock other)
{
return Offset.CompareTo(other.Offset);
}
}
private readonly List<MemoryBlock> _blocks = new List<MemoryBlock>();
public CacheMemoryAllocator(int capacity)
{
_blocks.Add(new MemoryBlock(0, capacity));
}
public int Allocate(int size)
{
for (int i = 0; i < _blocks.Count; i++)
{
MemoryBlock block = _blocks[i];
if (block.Size > size)
{
_blocks[i] = new MemoryBlock(block.Offset + size, block.Size - size);
return block.Offset;
}
else if (block.Size == size)
{
_blocks.RemoveAt(i);
return block.Offset;
}
}
// We don't have enough free memory to perform the allocation.
return -1;
}
public void Free(int offset, int size)
{
Insert(new MemoryBlock(offset, size));
}
private void Insert(MemoryBlock block)
{
int index = _blocks.BinarySearch(block);
if (index < 0)
{
index = ~index;
}
if (index < _blocks.Count)
{
MemoryBlock next = _blocks[index];
int endOffs = block.Offset + block.Size;
if (next.Offset == endOffs)
{
block = new MemoryBlock(block.Offset, block.Size + next.Size);
_blocks.RemoveAt(index);
}
}
if (index > 0)
{
MemoryBlock prev = _blocks[index - 1];
if (prev.Offset + prev.Size == block.Offset)
{
block = new MemoryBlock(block.Offset - prev.Size, block.Size + prev.Size);
_blocks.RemoveAt(--index);
}
}
_blocks.Insert(index, block);
}
}
}