CentralizedControl/Veldrid.Common/ImageRender/BatchGroup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Veldrid.Common
{
    public class BatchGroup
    {
        private BatchItem[] _items;

        public BatchGroup()
        {
            _items = new BatchItem[64];
        }
        public int Count { get; private set; }

        public ref BatchItem Add()
        {
            if (Count >= _items.Length)
            {
                var lastSize = _items.Length;
                var newSize = (lastSize + lastSize / 2 + 63) & (~63);
                Array.Resize(ref _items, newSize);
            }

            return ref _items[Count++];
        }

        public void Clear()
        {
            Count = 0;
        }

        public ReadOnlySpan<BatchItem> GetSpan() => new ReadOnlySpan<BatchItem>(_items, 0, Count);

        public Enumerator GetEnumerator() => new Enumerator(_items, Count);

        public struct Enumerator
        {
            private readonly BatchItem[] _items;
            private readonly int _count;
            private int _index;

            internal Enumerator(BatchItem[] items, int count)
            {
                _items = items;
                _count = count;
                _index = -1;
            }

            public BatchItem Current => _items[_index];

            public bool MoveNext()
            {
                if (_index >= _count)
                    return false;
                _index++;
                return true;
            }

            public void Reset()
            {
                _index = -1;
            }
        }
    }
}