ModernUO/Projects/Server/Serialization/IGenericReader.cs

/*************************************************************************
 * ModernUO                                                              *
 * Copyright 2019-2026 - ModernUO Development Team                       *
 * Email: hi@modernuo.com                                                *
 * File: IGenericReader.cs                                               *
 *                                                                       *
 * This program is free software: you can redistribute it and/or modify  *
 * it under the terms of the GNU General Public License as published by  *
 * the Free Software Foundation, either version 3 of the License, or     *
 * (at your option) any later version.                                   *
 *                                                                       *
 * You should have received a copy of the GNU General Public License     *
 * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 *************************************************************************/

using System;
using System.Buffers;
using System.Collections;
using System.IO;
using System.Net;

namespace Server;

public interface IGenericReader
{
    string ReadString(bool intern = false);
    public string ReadStringRaw(bool intern = false);

    long ReadLong();
    ulong ReadULong();
    int ReadInt();
    uint ReadUInt();
    short ReadShort();
    ushort ReadUShort();
    double ReadDouble();
    float ReadFloat();
    byte ReadByte();
    sbyte ReadSByte();
    bool ReadBool();
    Serial ReadSerial();
    Type ReadType();

    DateTime ReadDateTime() => new(ReadLong(), DateTimeKind.Utc);
    TimeSpan ReadTimeSpan() => new(ReadLong());

    /// <summary>
    /// Decodes a legacy delta-time value. Only for reading old-version payloads (version
    /// fallbacks and migration replays) — current formats store anchored time and read it
    /// with <see cref="ReadAnchoredTime" />. <see cref="IGenericWriter.WriteDeltaTime" /> is
    /// obsolete: no current-version format may write delta time.
    /// </summary>
    DateTime ReadDeltaTime()
    {
        return ReadLong() switch
        {
            long.MinValue => DateTime.MinValue,
            long.MaxValue => DateTime.MaxValue,
            var delta     => new DateTime(delta + DateTime.UtcNow.Ticks, DateTimeKind.Utc)
        };
    }

    /// <summary>
    /// Elapsed time between the loaded save starting and this load, applied by
    /// <see cref="ReadAnchoredTime" />. Zero when the source carries no anchor.
    /// </summary>
    TimeSpan AnchoredTimeShift => TimeSpan.Zero;

    /// <summary>
    /// UTC start of the loaded save. <see cref="ReadAnchoredTime" /> leaves a value at or before
    /// it unshifted. Default when unknown, which shifts every value.
    /// </summary>
    DateTime AnchoredTimeOrigin => default;

    /// <summary>
    /// Reads an anchored timestamp. A deadline still in the future when the save started is
    /// shifted by <see cref="AnchoredTimeShift" />, so it keeps the time it had left. A value at or
    /// before the save start is returned as saved: an expired deadline stays expired instead of
    /// coming back, and a record of something that already happened (a last-use or last-loss stamp)
    /// keeps its bytes across restarts, with downtime counting toward its window.
    /// </summary>
    DateTime ReadAnchoredTime()
    {
        var value = ReadDateTime();

        if (value == DateTime.MinValue || value == DateTime.MaxValue)
        {
            return value;
        }

        var shift = AnchoredTimeShift;
        if (shift == TimeSpan.Zero || value <= AnchoredTimeOrigin)
        {
            return value;
        }

        var ticks = value.Ticks + shift.Ticks;

        if (ticks >= DateTime.MaxValue.Ticks)
        {
            return DateTime.MaxValue;
        }

        return ticks <= 0 ? DateTime.MinValue : new DateTime(ticks, DateTimeKind.Utc);
    }
    decimal ReadDecimal() => new([ReadInt(), ReadInt(), ReadInt(), ReadInt()]);
    int ReadEncodedInt()
    {
        int v = 0, shift = 0;
        byte b;

        do
        {
            b = ReadByte();
            v |= (b & 0x7F) << shift;
            shift += 7;
        }
        while (b >= 0x80);

        return v;
    }
    IPAddress ReadIPAddress()
    {
        var length = ReadByte();
        // Either 2 ushorts, or 8 ushorts
        Span<byte> integer = stackalloc byte[length];
        Read(integer);
        return Utility.Intern(new IPAddress(integer));
    }
    Point3D ReadPoint3D() => new(ReadInt(), ReadInt(), ReadInt());
    Point2D ReadPoint2D() => new(ReadInt(), ReadInt());
    Rectangle2D ReadRect2D() => new(ReadPoint2D(), ReadPoint2D());
    Rectangle3D ReadRect3D() => new(ReadPoint3D(), ReadPoint3D());
    Map ReadMap() => Map.Maps[ReadByte()];
    Race ReadRace() => Race.Races[ReadByte()];
    int Read(Span<byte> buffer);
    unsafe T ReadEnum<T>() where T : unmanaged, Enum
    {
        switch (sizeof(T))
        {
            case 1:
                {
                    var num = ReadByte();
                    return *(T*)&num;
                }
            case 2:
                {
                    var num = ReadShort();
                    return *(T*)&num;
                }
            case 4:
                {
                    var num = ReadEncodedInt();
                    return *(T*)&num;
                }
            case 8:
                {
                    var num = ReadLong();
                    return *(T*)&num;
                }
        }

        return default;
    }
    Guid ReadGuid()
    {
        Span<byte> bytes = stackalloc byte[16];
        Read(bytes);
        return new Guid(bytes);
    }

    public BitArray ReadBitArray()
    {
        var bitLength = ReadEncodedInt();
        var byteLength = (bitLength + 7) / 8;

        var buffer = ArrayPool<byte>.Shared.Rent(byteLength);
        try
        {
            Read(buffer.AsSpan(0, byteLength));
            return new BitArray(buffer) { Length = bitLength };
        }
        finally
        {
            ArrayPool<byte>.Shared.Return(buffer);
        }
    }

    TextDefinition ReadTextDefinition()
    {
        return ReadEncodedInt() switch
        {
            0 => TextDefinition.Empty,
            1 => ReadEncodedInt(),
            2 => ReadString(),
            _ => null
        };
    }

    long Seek(long offset, SeekOrigin origin);
}