Add support for seeking to arbitrary ticks

[saul]

This PR adds a new SeekToTickAsync method that can jump to arbitrary ticks within the demo. It supports seeking backwards and forwards, and makes use of Source 2 demo 'snapshot' ticks to do this efficiently.

• [x] Refactor the code out of DemoParser.cs
• [x] Add unit tests

Closes #47

[github-actions[bot]]

BenchmarkDotNet v0.13.9+228a464e8be6c580ad9408e98f18813f6407fb5a, Ubuntu 22.04.4 LTS (Jammy Jellyfish)
AMD EPYC 7763, 1 CPU, 4 logical and 2 physical cores
.NET SDK 8.0.200
  [Host]     : .NET 8.0.2 (8.0.224.6711), X64 RyuJIT AVX2
  Job-LFXIPO : .NET 8.0.2 (8.0.224.6711), X64 RyuJIT AVX2
  Job-KRGKAI : .NET 8.0.2 (8.0.224.6711), X64 RyuJIT AVX2

InvocationCount=1  MaxIterationCount=16  UnrollFactor=1  
WarmupCount=1  

Method	Job	Arguments	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
ParseDemo	Job-LFXIPO	/p:Baseline=true	2.335 s	0.0972 s	0.0955 s	1.00	0.00	6000.0000	1000.0000	594.31 MB	1.00
ParseDemo	Job-KRGKAI	Default	2.195 s	0.0119 s	0.0106 s	0.95	0.04	5000.0000	2000.0000	489.9 MB	0.82

[in0finite]

when i do this:

        await demo.StartReadingAsync(File.OpenRead(path), default);

        await demo.SeekToTickAsync(new DemoTick(500), default);

it gives me:

System.IndexOutOfRangeException
  HResult=0x80131508
  Message=Index was outside the bounds of the array.
  Source=DemoFile
  StackTrace:
   at DemoFile.DemoParser.OnPacketEntities(CSVCMsg_PacketEntities msg) in /_/src/DemoFile/DemoParser.Entities.cs:line 418
   at DemoFile.PacketEvents.ParseNetMessage(Int32 msgType, ReadOnlySpan`1 buf) in /_/src/DemoFile/PacketEvents.cs:line 136
   at DemoFile.DemoParser.OnDemoPacket(CDemoPacket msg) in /_/src/DemoFile/DemoParser.cs:line 134
   at DemoFile.DemoParser.OnDemoFullPacket(CDemoFullPacket fullPacket) in /_/src/DemoFile/DemoParser.FullPacket.cs:line 157
   at DemoFile.DemoEvents.ReadDemoCommand(EDemoCommands msgType, ReadOnlySpan`1 buffer) in /_/src/DemoFile/DemoEvents.cs:line 48
   at DemoFile.DemoParser.<MoveNextCoreAsync>d__67.MoveNext() in /_/src/DemoFile/DemoParser.cs:line 287
   at System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1.ConfiguredValueTaskAwaiter.GetResult()
   at DemoFile.DemoParser.<SeekToTickAsync>d__125.MoveNext() in /_/src/DemoFile/DemoParser.FullPacket.cs:line 98
   at Program.<Main>d__0.MoveNext()
   at Program.<Main>(String[] args)

[saul]

Just pushed a fix for the IndexOutOfRangeException - can you try now?

[in0finite]

If I seek to 5000, it gives me 1 player death event, when I seek to 50000, there are no death events. Is this expected ?

[in0finite]

Also, for match (map Overpass) : https://www.hltv.org/matches/2369507/faze-vs-spirit-iem-katowice-2024 I get this:

Unhandled exception. System.Exception: Delta on non-existent entity 1
   at DemoFile.DemoParser.OnPacketEntities(CSVCMsg_PacketEntities msg) in /_/src/DemoFile/DemoParser.Entities.cs:line 366
   at DemoFile.PacketEvents.ParseNetMessage(Int32 msgType, ReadOnlySpan`1 buf) in /_/src/DemoFile/PacketEvents.cs:line 136
   at DemoFile.DemoParser.OnDemoPacket(CDemoPacket msg) in /_/src/DemoFile/DemoParser.cs:line 134
   at DemoFile.DemoEvents.ReadDemoCommand(EDemoCommands msgType, ReadOnlySpan`1 buffer) in /_/src/DemoFile/DemoEvents.cs:line 33
   at DemoFile.DemoParser.MoveNextCoreAsync(EDemoCommands msgType, Boolean isCompressed, Int32 size, CancellationToken cancellationToken) in /_/src/DemoFile/DemoParser.cs:line 303
   at DemoFile.DemoParser.SeekToTickAsync(DemoTick targetTick, CancellationToken cancellationToken) in /_/src/DemoFile/DemoParser.FullPacket.cs:line 98
   at Program.Main(String[] args) in /_/examples/DemoFile.Example.Basic/Program.cs:line 19
   at Program.<Main>(String[] args)

[saul]

You can't depend on game events etc. occuring while seeking. This is the reason why Valve removed the round_start/end events as you can't rely on them to know when rounds are starting and finishing.

As for this:

Unhandled exception. System.Exception: Delta on non-existent entity 1

Please can you share the code that reproduces the exception?

[in0finite]

Please can you share the code that reproduces the exception?

var path = "test.dem";

var demo = new DemoParser();

demo.Source1GameEvents.PlayerDeath += e =>
{
    Console.WriteLine($"{e.Attacker?.PlayerName} [{e.Weapon}] {e.Player?.PlayerName}");
};

await demo.StartReadingAsync(File.OpenRead(path), default);

await demo.SeekToTickAsync(new DemoTick(50000), default);

[in0finite]

You can't depend on game events etc. occuring while seeking

But why are game events firing while seeking ? In my understanding, parser should ignore all events (and entity changes) while seeking.

[saul]

I've just pushed another change that should fix the seeking to tick 50,000 issue

[in0finite]

It works now, but game events are still being fired. Is it possible to seek without invoking any callbacks ? Or without parsing anything except StringTables ?

[in0finite]

I get some weird error:

Unhandled exception. System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')
   at System.Collections.Generic.List`1.set_Item(Int32 index, T value)
   at DemoFile.StringTable.ReadUpdate(ReadOnlySpan`1 stringData, Int32 entries) in /_/src/DemoFile/StringTable.cs:line 126
   at DemoFile.DemoParser.OnUpdateStringTable(CSVCMsg_UpdateStringTable msg) in /_/src/DemoFile/DemoParser.StringTables.cs:line 61
   at DemoFile.PacketEvents.ParseNetMessage(Int32 msgType, ReadOnlySpan`1 buf) in /_/src/DemoFile/PacketEvents.cs:line 106
   at DemoFile.DemoParser.OnDemoPacket(CDemoPacket msg) in /_/src/DemoFile/DemoParser.cs:line 134
   at DemoFile.DemoEvents.ReadDemoCommandCore[T](Action`1 callback, MessageParser`1 parser, ReadOnlySpan`1 buffer, Boolean isCompressed) in /_/src/DemoFile/DemoEvents.cs:line 79
   at DemoFile.DemoEvents.ReadDemoCommand(EDemoCommands msgType, ReadOnlySpan`1 buffer, Boolean isCompressed) in /_/src/DemoFile/DemoEvents.cs:line 37
   at DemoFile.DemoParser.MoveNextCoreAsync(EDemoCommands msgType, Boolean isCompressed, Int32 size, CancellationToken cancellationToken) in /_/src/DemoFile/DemoParser.cs:line 301
   at Program.TestBug(String path) in /_/examples/DemoFile.Example.Basic/Program.cs:line 73

with this code :

public static async Task TestBug(string path)
{
    var stream = new MemoryStream(File.ReadAllBytes(path));

    var demo = new DemoParser();

    await demo.StartReadingAsync(stream, default);

    var tickCount = demo.TickCount.Value;

    const int FullPacketInterval = 64 * 60;

    for (int i = FullPacketInterval * 4; i <= tickCount; i += FullPacketInterval)
    {
        Console.WriteLine($"Seeking to tick {i}");

        demo = new DemoParser();

        //stream = new MemoryStream(File.ReadAllBytes(path));
        stream.Position = 0;
        await demo.StartReadingAsync(stream, default);

        await demo.SeekToTickAsync(new DemoTick(i), default);

        while (await demo.MoveNextAsync(default))
        {
        }
    }
}

[saul]

This is because DemFullPackets only contains the string tables that changed since the last DemFullPacket.

I'm going to have to rethink how stringtables are stored to allow seeking. Will let you know when I've pushed a fix.