ValueStringBuilder.cs

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using System.Buffers;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
 
namespace System.Text;
 
[DefaultMember("Item")]
internal ref struct ValueStringBuilder
{
    private char[] _arrayToReturnToPool;
 
    private Span<char> _chars;
 
    private int _pos;
 
    public int Length
    {
        set
        {
            _pos = value;
        }
    }
 
    public int Capacity => _chars.Length;
 
    public ValueStringBuilder(Span<char> initialBuffer)
    {
        _arrayToReturnToPool = null;
        _chars = initialBuffer;
        _pos = 0;
    }
 
    public void EnsureCapacity(int capacity)
    {
        if ((uint)capacity > (uint)_chars.Length)
        {
            Grow(capacity - _pos);
        }
    }
 
    public ref char GetPinnableReference()
    {
        return ref MemoryMarshal.GetReference(_chars);
    }
 
    public override string ToString()
    {
        string result = _chars.Slice(0, _pos).ToString();
        Dispose();
        return result;
    }
 
    [MethodImpl(MethodImplOptions.NoInlining)]
    private void Grow(int additionalCapacityBeyondPos)
    {
        char[] array = ArrayPool<char>.Shared.Rent((int)Math.Max((uint)(_pos + additionalCapacityBeyondPos), (uint)(_chars.Length * 2)));
        _chars.Slice(0, _pos).CopyTo(array);
        char[] arrayToReturnToPool = _arrayToReturnToPool;
        _chars = (_arrayToReturnToPool = array);
        if (arrayToReturnToPool != null)
        {
            ArrayPool<char>.Shared.Return(arrayToReturnToPool);
        }
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public void Dispose()
    {
        char[] arrayToReturnToPool = _arrayToReturnToPool;
        this = default(System.Text.ValueStringBuilder);
        if (arrayToReturnToPool != null)
        {
            ArrayPool<char>.Shared.Return(arrayToReturnToPool);
        }
    }
}