Supercell.GUT/Supercell.GUT.Titan/Encoding/ChecksumEncoder.cs

using Supercell.GUT.Titan.Math;
using System.Runtime.CompilerServices;

namespace Supercell.GUT.Titan.Encoding;
public class ChecksumEncoder
{
    private int _checksum;
    private int _snapshotChecksum;

    public ChecksumEncoder()
    {
        IsChecksumEnabled = true;
    }

    public virtual bool IsCheckSumOnlyMode => true;

    public virtual ChecksumEncoder WriteBoolean(bool value) => UpdateCheckSum(value ? 13 : 7);

    public virtual ChecksumEncoder WriteByte(byte value) => UpdateCheckSum(value + 11);

    public virtual ChecksumEncoder WriteShort(short value) => UpdateCheckSum(value + 19);

    public virtual ChecksumEncoder WriteInt(int value) => UpdateCheckSum(value + 9);

    public virtual void WriteLong(LogicLong value) => value.Encode(this);

    public virtual ChecksumEncoder WriteString(string? value) =>
        UpdateCheckSum(value != null ? value.Length + 28 : 27);

    public virtual ChecksumEncoder WriteBytes(ReadOnlySpan<byte> value) =>
        UpdateCheckSum(value.Length + 28);

    public bool IsChecksumEnabled { get; private set; }

    public int CheckSum => IsChecksumEnabled ? _checksum : _snapshotChecksum;

    public ChecksumEncoder EnableCheckSum(bool enable)
    {
        if (!IsChecksumEnabled && enable)
        {
            _checksum = _snapshotChecksum;
        }
        else
        {
            _snapshotChecksum = _checksum;
        }

        IsChecksumEnabled = enable;
        return this;
    }

    public ChecksumEncoder ResetCheckSum()
    {
        _checksum = 0;
        return this;
    }

    public override bool Equals(object? obj)
    {
        ChecksumEncoder? otherEncoder = obj as ChecksumEncoder;
        return otherEncoder?.CheckSum == CheckSum;
    }

    public override int GetHashCode()
    {
        // original: Debugger::error("ChecksumEncoder hashCode not designed");
        return CheckSum;
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private ChecksumEncoder UpdateCheckSum(int value)
    {
        _checksum = value + Ror4(_checksum, 31);
        return this;
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static int Ror4(int v, int c) => v >> c | v << 32 - c;
}