Supercell.GUT/Supercell.GUT.Titan/Encoding/Streamed/ByteStream.cs

using Supercell.GUT.Titan.Math;
using System.Buffers.Binary;
using System.Runtime.CompilerServices;
using TextEncoding = System.Text.Encoding;

namespace Supercell.GUT.Titan.Encoding.Streamed;

public class ByteStream : ChecksumEncoder
{
    public byte[] Buffer { get; set; }

    private int _bitIndex;
    private int _length;

    public int Offset { get; set; }

    public int Length => _length > 0 ? _length : Offset;

    public ByteStream(byte[] buffer, int length)
    {
        Buffer = buffer;
        _length = length;
    }

    public ByteStream(int capacity)
    {
        Buffer = new byte[capacity];
    }

    public ByteStream()
    {
        Buffer = new byte[10];
    }

    public void SetByteArray(byte[] buffer, int length)
    {
        Buffer = buffer;
        _length = length;
    }

    public bool ReadBoolean()
    {
        if (_bitIndex == 0)
            ++Offset;

        bool value = (Buffer[Offset - 1] & 1 << _bitIndex) != 0;
        _bitIndex = _bitIndex + 1 & 7;
        return value;
    }

    public byte ReadByte()
    {
        _bitIndex = 0;
        return Buffer[Offset++];
    }

    public short ReadShort()
    {
        _bitIndex = 0;

        short ret = BinaryPrimitives.ReadInt16BigEndian(Buffer.AsSpan()[Offset..]);
        Offset += 2;

        return ret;
    }

    public int ReadInt()
    {
        _bitIndex = 0;

        int ret = BinaryPrimitives.ReadInt32BigEndian(Buffer.AsSpan()[Offset..]);
        Offset += 4;

        return ret;
    }

    public int ReadVInt()
    {
        _bitIndex = 0;

        int value = 0;
        byte byteValue = Buffer[Offset++];

        if ((byteValue & 0x40) != 0)
        {
            value |= byteValue & 0x3F;

            if ((byteValue & 0x80) != 0)
            {
                value |= ((byteValue = Buffer[Offset++]) & 0x7F) << 6;

                if ((byteValue & 0x80) != 0)
                {
                    value |= ((byteValue = Buffer[Offset++]) & 0x7F) << 13;

                    if ((byteValue & 0x80) != 0)
                    {
                        value |= ((byteValue = Buffer[Offset++]) & 0x7F) << 20;

                        if ((byteValue & 0x80) != 0)
                        {
                            value |= ((_ = Buffer[Offset++]) & 0x7F) << 27;
                            return (int)(value | 0x80000000);
                        }

                        return (int)(value | 0xF8000000);
                    }

                    return (int)(value | 0xFFF00000);
                }

                return (int)(value | 0xFFFFE000);
            }

            return (int)(value | 0xFFFFFFC0);
        }

        value |= byteValue & 0x3F;

        if ((byteValue & 0x80) != 0)
        {
            value |= ((byteValue = Buffer[Offset++]) & 0x7F) << 6;

            if ((byteValue & 0x80) != 0)
            {
                value |= ((byteValue = Buffer[Offset++]) & 0x7F) << 13;

                if ((byteValue & 0x80) != 0)
                {
                    value |= ((byteValue = Buffer[Offset++]) & 0x7F) << 20;

                    if ((byteValue & 0x80) != 0)
                    {
                        value |= ((_ = Buffer[Offset++]) & 0x7F) << 27;
                    }
                }
            }
        }

        return value;
    }

    public LogicLong ReadLong()
    {
        LogicLong ll = new();
        ll.Decode(this);

        return ll;
    }

    public string? ReadString()
    {
        int length = ReadInt();
        if (length is < 0 or > 900000)
            return null;
        else if (length == 0)
            return string.Empty;

        string ret = TextEncoding.UTF8.GetString(Buffer, Offset, length);
        Offset += length;

        return ret;
    }

    public string ReadStringReference()
    {
        int length = ReadInt();
        if (length is <= 0 or > 900000) return string.Empty;

        string ret = TextEncoding.UTF8.GetString(Buffer, Offset, length);
        Offset += length;

        return ret;
    }

    public byte[] ReadBytes(int length)
    {
        _bitIndex = 0;

        byte[] ret = Buffer.Skip(Offset).Take(length).ToArray();
        Offset += length;

        return ret;
    }

    public override ChecksumEncoder WriteBoolean(bool value)
    {
        base.WriteBoolean(value);

        if (_bitIndex == 0)
        {
            EnsureCapacity(1);
            Buffer[Offset++] = 0;
        }

        Buffer[Offset - 1] |= (byte)(value ? 1 : 0);
        _bitIndex = _bitIndex + 1 & 7;

        return this;
    }

    public override ChecksumEncoder WriteByte(byte value)
    {
        base.WriteByte(value);
        EnsureCapacity(1);

        Buffer[Offset++] = value;

        return this;
    }

    public override ChecksumEncoder WriteShort(short value)
    {
        base.WriteShort(value);
        EnsureCapacity(2);

        BinaryPrimitives.WriteInt16BigEndian(Buffer.AsSpan()[Offset..], value);
        Offset += 2;

        return this;
    }

    public override ChecksumEncoder WriteInt(int value)
    {
        base.WriteInt(value);
        EnsureCapacity(4);

        WriteIntToByteArray(value);
        return this;
    }

    public override ChecksumEncoder WriteString(string? value)
    {
        base.WriteString(value);
        if (value == null)
        {
            WriteIntToByteArray(-1);
            return this;
        }

        int size = TextEncoding.UTF8.GetByteCount(value);
        WriteIntToByteArray(size);

        EnsureCapacity(size);
        TextEncoding.UTF8.GetBytes(value, Buffer.AsSpan()[Offset..]);

        Offset += size;
        return this;
    }

    public override ChecksumEncoder WriteBytes(ReadOnlySpan<byte> value)
    {
        base.WriteBytes(value);

        WriteIntToByteArray(value.Length);

        EnsureCapacity(value.Length);
        value.CopyTo(Buffer.AsSpan()[Offset..]);
        Offset += value.Length;

        return this;
    }

    public override bool IsCheckSumOnlyMode => false;

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private void WriteIntToByteArray(int value)
    {
        EnsureCapacity(4);

        BinaryPrimitives.WriteInt32BigEndian(Buffer.AsSpan()[Offset..], value);
        Offset += 4;
    }

    public void EnsureCapacity(int capacity)
    {
        _bitIndex = 0;
        int bufferLength = Buffer.Length;

        if (Offset + capacity > bufferLength)
        {
            byte[] tmpBuffer = new byte[Buffer.Length + capacity + 100];
            System.Buffer.BlockCopy(Buffer, 0, tmpBuffer, 0, bufferLength);
            Buffer = tmpBuffer;
        }
    }

    public bool IsAtEnd()
    {
        return Offset >= Buffer.Length;
    }

    public void ResetOffset()
    {
        this.Offset = 0;
    }

    public void Destruct()
    {
        ;
    }
}