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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.Syntax.InternalSyntax
{
internal class SyntaxListPool
{
private ArrayElement<SyntaxListBuilder?>[] _freeList = new ArrayElement<SyntaxListBuilder?>[10];
private int _freeIndex;
#if DEBUG
private readonly List<SyntaxListBuilder> _allocated = new List<SyntaxListBuilder>();
#endif
internal SyntaxListPool()
{
}
internal SyntaxListBuilder Allocate()
{
SyntaxListBuilder item;
if (_freeIndex > 0)
{
_freeIndex--;
item = _freeList[_freeIndex].Value!;
_freeList[_freeIndex].Value = null;
}
else
{
item = new SyntaxListBuilder(10);
}
#if DEBUG
Debug.Assert(!_allocated.Contains(item));
_allocated.Add(item);
#endif
return item;
}
internal SyntaxListBuilder<TNode> Allocate<TNode>() where TNode : GreenNode
{
return new SyntaxListBuilder<TNode>(this.Allocate());
}
internal SeparatedSyntaxListBuilder<TNode> AllocateSeparated<TNode>() where TNode : GreenNode
{
return new SeparatedSyntaxListBuilder<TNode>(this.Allocate());
}
internal void Free<TNode>(in SeparatedSyntaxListBuilder<TNode> item) where TNode : GreenNode
{
Free(item.UnderlyingBuilder);
}
internal void Free(SyntaxListBuilder? item)
{
if (item is null)
return;
item.Clear();
if (_freeIndex >= _freeList.Length)
{
this.Grow();
}
#if DEBUG
Debug.Assert(_allocated.Contains(item));
_allocated.Remove(item);
#endif
_freeList[_freeIndex].Value = item;
_freeIndex++;
}
private void Grow()
{
var tmp = new ArrayElement<SyntaxListBuilder?>[_freeList.Length * 2];
Array.Copy(_freeList, tmp, _freeList.Length);
_freeList = tmp;
}
public SyntaxList<TNode> ToListAndFree<TNode>(SyntaxListBuilder<TNode> item)
where TNode : GreenNode
{
if (item.IsNull)
return default;
var list = item.ToList();
Free(item);
return list;
}
public SeparatedSyntaxList<TNode> ToListAndFree<TNode>(in SeparatedSyntaxListBuilder<TNode> item)
where TNode : GreenNode
{
var list = item.ToList();
Free(item);
return list;
}
}
}
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