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rewritten BufferedEnumerator to reduce number of allocations to 1

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Timerix 2025-04-05 08:02:37 +05:00
parent e9c7c8f5c1
commit b0fefbf667
1 changed files with 55 additions and 17 deletions
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72
ParadoxSaveParser.Lib/BufferedEnumerator.cs
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@ -37,35 +37,73 @@ namespace ParadoxSaveParser.Lib;
/// 2 3 | 4 | 5
/// 3 4 | 5 |
/// </code>
public class BufferedEnumerator<T> : IEnumerator<LinkedListNode<T>>
public class BufferedEnumerator<T> : IEnumerator<BufferedEnumerator<T>.Node>
{
private readonly int _bufferSize;
private LinkedListNode<T>? _currentNode;
private int _currentNodeIndex = -1;
public class Node
{
#nullable disable
public Node Previous;
public Node Next;
public T Value;
#nullable enable
}
private readonly IEnumerator<T> _enumerator;
private readonly LinkedList<T> _llist = new();
private readonly Node[] _ringBuffer;
private Node? _currentNode;
private int _currentBufferIndex = -1;
private int _lastValueIndex = -1;
public BufferedEnumerator(IEnumerator<T> enumerator, int bufferSize)
{
_enumerator = enumerator;
_bufferSize = bufferSize;
_ringBuffer = new Node[bufferSize];
}
private void InitBuffer()
{
_ringBuffer[0] = new Node
{
Value = default!
};
for (int i = 1; i < _ringBuffer.Length; i++)
{
_ringBuffer[i] = new Node
{
Previous = _ringBuffer[i - 1],
Value = default!,
};
_ringBuffer[i - 1].Next = _ringBuffer[i];
}
_ringBuffer[^1].Next = _ringBuffer[0];
_ringBuffer[0].Previous = _ringBuffer[^1];
}
public bool MoveNext()
{
if (_currentNodeIndex >= _bufferSize / 2)
_llist.RemoveFirst();
while (_llist.Count < _bufferSize && _enumerator.MoveNext())
if (_currentBufferIndex == -1)
{
_llist.AddLast(_enumerator.Current);
InitBuffer();
int beforeMidpoint = _ringBuffer.Length / 2 - 1;
for (int i = 0; i <= beforeMidpoint && _enumerator.MoveNext(); i++)
{
_ringBuffer[i].Value = _enumerator.Current;
}
}
if (_llist.Count == 0)
_currentBufferIndex = (_currentBufferIndex + 1) % _ringBuffer.Length;
if (_enumerator.MoveNext())
{
int midpoint = (_currentBufferIndex + _ringBuffer.Length / 2) % _ringBuffer.Length;
_ringBuffer[midpoint].Value = _enumerator.Current;
_lastValueIndex = midpoint;
}
if(_currentBufferIndex == (_lastValueIndex + 1) % _ringBuffer.Length)
return false;
_currentNodeIndex++;
_currentNode = _currentNode is null ? _llist.First : _currentNode.Next;
return _currentNode is not null;
_currentNode = _ringBuffer[_currentBufferIndex];
return true;
}
public void Reset()
@ -73,7 +111,7 @@ public class BufferedEnumerator<T> : IEnumerator<LinkedListNode<T>>
throw new NotImplementedException();
}
public LinkedListNode<T> Current => _currentNode!;
public Node Current => _currentNode!;
object IEnumerator.Current => Current;