SegmentStringBuilder.cs

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using System.Buffers;
using System.Diagnostics;
using System.Runtime.CompilerServices;
 
namespace System.Text;
 
[DebuggerDisplay("Count = {_count}")]
internal struct SegmentStringBuilder
{
    private ReadOnlyMemory<char>[] _array;
 
    private int _count;
 
    public int Count => _count;
 
    public static SegmentStringBuilder Create()
    {
        SegmentStringBuilder result = default(SegmentStringBuilder);
        result._array = Array.Empty<ReadOnlyMemory<char>>();
        return result;
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public void Add(ReadOnlyMemory<char> segment)
    {
        ReadOnlyMemory<char>[] array = _array;
        int count = _count;
        if ((uint)count < (uint)array.Length)
        {
            array[count] = segment;
            _count = count + 1;
        }
        else
        {
            GrowAndAdd(segment);
        }
    }
 
    [MethodImpl(MethodImplOptions.NoInlining)]
    private void GrowAndAdd(ReadOnlyMemory<char> segment)
    {
        ReadOnlyMemory<char>[] array = _array;
        int minimumLength = ((array.Length == 0) ? 256 : (array.Length * 2));
        ReadOnlyMemory<char>[] array2 = (_array = ArrayPool<ReadOnlyMemory<char>>.Shared.Rent(minimumLength));
        Array.Copy(array, array2, _count);
        ArrayPool<ReadOnlyMemory<char>>.Shared.Return(array, clearArray: true);
        array2[_count++] = segment;
    }
 
    public Span<ReadOnlyMemory<char>> AsSpan()
    {
        return new Span<ReadOnlyMemory<char>>(_array, 0, _count);
    }
 
    public override string ToString()
    {
        ReadOnlyMemory<char>[] array = _array;
        Span<ReadOnlyMemory<char>> span = new Span<ReadOnlyMemory<char>>(array, 0, _count);
        int num = 0;
        for (int i = 0; i < span.Length; i++)
        {
            num += span[i].Length;
        }
        string result = string.Create(num, this, delegate(Span<char> dest, SegmentStringBuilder builder)
        {
            Span<ReadOnlyMemory<char>> span2 = builder.AsSpan();
            for (int j = 0; j < span2.Length; j++)
            {
                ReadOnlySpan<char> span3 = span2[j].Span;
                span3.CopyTo(dest);
                dest = dest.Slice(span3.Length);
            }
        });
        span.Clear();
        this = default(SegmentStringBuilder);
        ArrayPool<ReadOnlyMemory<char>>.Shared.Return(array);
        return result;
    }
}