Toolkit2/Toolkit.UI.Controls.Avalonia/QrCode/Encoding/BitList.cs

using System.Collections;

namespace Gma.QrCodeNet.Encoding;

internal sealed class BitList : IEnumerable<bool>
{
    internal BitList()
    {
        Count = 0;
        List = new List<byte>(32);
    }

    internal BitList(IEnumerable<byte> byteArray)
    {
        Count = byteArray.Count();
        List = byteArray.ToList();
    }

    internal List<byte> List { get; }

    internal int Count { get; private set; }

    internal bool this[int index]
    {
        get
        {
            if (index < 0 || index >= Count)
            {
                throw new ArgumentOutOfRangeException(nameof(index), "Index out of range");
            }

            int value_Renamed = List[index >> 3] & 0xff;
            return ((value_Renamed >> (7 - (index & 0x7))) & 1) == 1;
        }
    }

    public IEnumerator<bool> GetEnumerator()
    {
        int numBytes = Count >> 3;
        int remainder = Count & 0x7;
        byte value;
        for (int index = 0; index < numBytes; index++)
        {
            value = List[index];
            for (int shiftNum = 7; shiftNum >= 0; shiftNum--)
            {
                yield return ((value >> shiftNum) & 1) == 1;
            }
        }
        if (remainder > 0)
        {
            value = List[numBytes];
            for (int index = 0; index < remainder; index++)
            {
                yield return ((value >> (7 - index)) & 1) == 1;
            }
        }
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    private int ToBit(bool item)
    {
        return item ? 1 : 0;
    }

    internal void Add(bool item)
    {
        int numBitsinLastByte = Count & 0x7;

        // Add one more byte to List when we have no bits in the last byte.
        if (numBitsinLastByte == 0)
        {
            List.Add(0);
        }

        List[Count >> 3] |= (byte)(ToBit(item) << (7 - numBitsinLastByte));
        Count++;
    }

    internal void Add(IEnumerable<bool> items)
    {
        foreach (bool item in items)
        {
            Add(item);
        }
    }

    internal void Add(int value, int bitCount)
    {
        if (bitCount is < 0 or > 32)
        {
            throw new ArgumentOutOfRangeException(nameof(bitCount), $"{nameof(bitCount)} must be greater than or equal to 0");
        }

        int numBitsLeft = bitCount;

        while (numBitsLeft > 0)
        {
            if ((Count & 0x7) == 0 && numBitsLeft >= 8)
            {
                // Add one more byte to List.
                byte newByte = (byte)((value >> (numBitsLeft - 8)) & 0xFF);
                AppendByte(newByte);
                numBitsLeft -= 8;
            }
            else
            {
                bool bit = ((value >> (numBitsLeft - 1)) & 1) == 1;
                Add(bit);
                numBitsLeft--;
            }
        }
    }

    private void AppendByte(byte item)
    {
        List.Add(item);
        Count += 8;
    }
}