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feat(net): CreateObject body parser — GUID + Position + SetupId extracted (Phase 4.7d)

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Decodes the CreateObject (0xF745) game message body far enough to hand
an entity off to acdream's existing IGameState/MeshRenderer pipeline.
Ported from ACE's WorldObject_Networking.cs (SerializeCreateObject,
SerializeModelData, SerializePhysicsData) and Position.cs.

Scope: the parser extracts exactly three fields —
  - GUID (u32 right after the opcode)
  - ServerPosition (landblockId + XYZ + rotation quaternion), if the
    Position bit is set in the PhysicsDescriptionFlag
  - SetupTableId (setup dat id for the visual mesh chain), if the
    CSetup bit is set

Everything else in a CreateObject body (weenie header, object description,
motion tables, palettes, texture overrides, animation frames, velocity,
acceleration, omega, scale, friction, elasticity, translucency,
default scripts, sequence timestamps, ...) is consumed-or-skipped with
just enough bytes to advance past the correct flag-gated sections.
The parser stops at the end of PhysicsData — we don't need weenie-header
fields for rendering placement.

Components parsed in order (all from ACE's serialize routines):
  1. Opcode u32 (must be 0xF745)
  2. u32 GUID
  3. ModelData header (byte 0x11 marker, byte subPaletteCount,
     byte textureChangeCount, byte animPartChangeCount), followed by
     PackedDword palette/subPalette fields, texture change records,
     anim part change records, aligned to 4 bytes at end
  4. u32 PhysicsDescriptionFlag
  5. u32 PhysicsState (skipped)
  6. Conditional Movement/AnimationFrame section
  7. Conditional Position section (LandblockId, X, Y, Z, RW, RX, RY, RZ)
  8. Conditional MTable/STable/PeTable u32 ids (all skipped)
  9. Conditional CSetup u32 (extracted as SetupTableId)

The PackedDword reader is a new helper: AC's variable-width uint format
where values ≤ 32767 encode as a u16, larger values use a marker bit in
the top of the first u16 and a continuation u16. Ported from
Extensions.WritePackedDword.

LIVE RUN AGAINST THE ACE SERVER (test account, Holtburg):

  step 4: CharacterList received account=testaccount count=2
    character: id=0x5000000A name=+Acdream
    character: id=0x50000008 name=+Wdw
  sent CharacterEnterWorldRequest
  step 6: CharacterEnterWorldServerReady received
  sent CharacterEnterWorld(guid=0x5000000A)
  step 8 summary: 83 GameMessages assembled, 68 CreateObject,
                  68 parsed, 52 w/position, 68 w/setup

  First 10 parsed CreateObjects:
    guid=0x5000000A lb=0xA9B40021 xyz=(104.89,15.05,94.01) setup=0x02000001
    guid=0x80000600 no position setup=0x02000181
    guid=0x800005FF no position setup=0x02000B77
    guid=0x80000603 no position setup=0x02000176
    guid=0x80000604 no position setup=0x02000D5C
    guid=0x80000694 no position setup=0x020005FF
    guid=0x80000697 no position setup=0x02000921
    guid=0x80000601 no position setup=0x02000179
    guid=0x80000605 no position setup=0x02000155
    guid=0x80000695 no position setup=0x020005FF

The first line is +Acdream himself — GUID matches what we picked from
CharacterList, landblock 0xA9B4 is Holtburg (the area we already render),
setup 0x02000001 is the default humanoid player mesh. The other 67 are
NPCs/weenies/scenery-weenies in the same area; the 16 without positions
are inventory items whose position is inherited from the parent.

ALL 68 CreateObjects parsed cleanly — no short reads, no format errors.
Phase 4.7d proves byte-level compatibility with ACE's outbound network
serialization format. The remaining Phase 4 work (WorldSession type +
GameWindow wiring) is glue code above a codec that now speaks the real
AC wire format.

Tests: 77 core + 83 net (+1 live test) = 161 passing, all green.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-04-11 15:18:54 +02:00
parent 94da385ff4
commit 9e4313f3d3
2 changed files with 295 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

263
src/AcDream.Core.Net/Messages/CreateObject.cs Normal file
View file

@ -0,0 +1,263 @@
using System.Buffers.Binary;
namespace AcDream.Core.Net.Messages;
/// <summary>
/// Inbound <c>CreateObject</c> GameMessage (opcode <c>0xF745</c>). This is
/// the primary spawn-an-entity-into-my-world message — the server sends
/// one for every visible weenie (players, creatures, items, scenery
/// weenies like the Holtburg foundry statue) in the client's loaded area.
///
/// <para>
/// acdream's parser extracts only the fields needed to hand the spawn off
/// to <c>IGameState</c>:
/// </para>
/// <list type="bullet">
/// <item><b>GUID</b> — always at the start of the body (after the opcode).</item>
/// <item><b>Position</b> (landblock id + local XYZ + rotation quaternion) — present
/// when <see cref="PhysicsDescriptionFlag.Position"/> is set in the physics
/// description flags. We need this to place the entity in the world.</item>
/// <item><b>SetupTableId</b> — present when <see cref="PhysicsDescriptionFlag.CSetup"/>
/// is set. This is the dat-id for the visual model
/// (<c>Setup</c>/<c>GfxObj</c> chain) that acdream's existing
/// SetupMesh + GfxObjMesh pipeline already knows how to render.</item>
/// </list>
///
/// <para>
/// All other fields (weenie header, object description, motion tables,
/// palettes, texture overrides, animation frames, velocity, ...) are
/// consumed-but-ignored so the parse position ends up wherever the
/// client-side caller wanted — a <c>Parse</c> call doesn't need to reach
/// the end of the body to return useful output. We stop after PhysicsData
/// since that's the last segment containing fields acdream cares about
/// in this phase.
/// </para>
///
/// <para>
/// Ported by reading <c>ACE/Source/ACE.Server/WorldObjects/WorldObject_Networking.cs</c>
/// (SerializeCreateObject, SerializeModelData, SerializePhysicsData) plus
/// <c>ACE.Entity/Position.cs</c> and <c>PhysicsDescriptionFlag.cs</c>.
/// See NOTICE.md.
/// </para>
/// </summary>
public static class CreateObject
{
public const uint Opcode = 0xF745u;
[Flags]
public enum PhysicsDescriptionFlag : uint
{
None = 0x000000,
CSetup = 0x000001,
MTable = 0x000002,
Velocity = 0x000004,
Acceleration = 0x000008,
Omega = 0x000010,
Parent = 0x000020,
Children = 0x000040,
ObjScale = 0x000080,
Friction = 0x000100,
Elasticity = 0x000200,
Timestamps = 0x000400,
STable = 0x000800,
PeTable = 0x001000,
DefaultScript = 0x002000,
DefaultScriptIntensity = 0x004000,
Position = 0x008000,
Movement = 0x010000,
AnimationFrame = 0x020000,
Translucency = 0x040000,
}
/// <summary>
/// The three fields acdream cares about. Position and SetupTableId are
/// nullable because their corresponding physics-description-flag bits
/// may not be set on every CreateObject.
/// </summary>
public readonly record struct Parsed(
uint Guid,
ServerPosition? Position,
uint? SetupTableId);
/// <summary>A server-side position: landblock id + local XYZ + unit quaternion rotation.</summary>
public readonly record struct ServerPosition(
uint LandblockId,
float PositionX, float PositionY, float PositionZ,
float RotationW, float RotationX, float RotationY, float RotationZ);
/// <summary>
/// Parse a reassembled CreateObject body. <paramref name="body"/> must
/// start with the 4-byte opcode. Returns <c>null</c> if the body is
/// malformed (truncated field); returns a populated <see cref="Parsed"/>
/// on success. The parser stops at the end of PhysicsData; subsequent
/// weenie-header fields are deliberately not consumed.
/// </summary>
public static Parsed? TryParse(ReadOnlySpan<byte> body)
{
try
{
int pos = 0;
uint opcode = ReadU32(body, ref pos);
if (opcode != Opcode)
return null;
uint guid = ReadU32(body, ref pos);
// --- ModelData ---
// Header: byte 0x11 marker, byte subPalettes, byte textureChanges, byte animPartChanges
if (body.Length - pos < 4) return null;
byte _marker = body[pos]; pos += 1;
byte subPaletteCount = body[pos]; pos += 1;
byte textureChangeCount = body[pos]; pos += 1;
byte animPartChangeCount = body[pos]; pos += 1;
if (subPaletteCount > 0)
_ = ReadPackedDword(body, ref pos); // overall palette id
for (int i = 0; i < subPaletteCount; i++)
{
_ = ReadPackedDword(body, ref pos); // subPaletteId
if (body.Length - pos < 2) return null;
pos += 2; // offset + length bytes
}
for (int i = 0; i < textureChangeCount; i++)
{
if (body.Length - pos < 1) return null;
pos += 1; // partIndex
_ = ReadPackedDword(body, ref pos); // oldTexture
_ = ReadPackedDword(body, ref pos); // newTexture
}
for (int i = 0; i < animPartChangeCount; i++)
{
if (body.Length - pos < 1) return null;
pos += 1; // index
_ = ReadPackedDword(body, ref pos); // animationId
}
AlignTo4(ref pos);
// --- PhysicsData ---
if (body.Length - pos < 8) return null;
var physicsFlags = (PhysicsDescriptionFlag)BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(pos));
pos += 4;
pos += 4; // PhysicsState (skip)
if ((physicsFlags & PhysicsDescriptionFlag.Movement) != 0)
{
// u32 length, length bytes of serialized MovementData, u32 isAutonomous flag
if (body.Length - pos < 4) return null;
uint movementLen = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(pos));
pos += 4;
if (movementLen > 0)
{
if (body.Length - pos < (int)movementLen) return null;
pos += (int)movementLen;
if (body.Length - pos < 4) return null;
pos += 4; // isAutonomous
}
}
else if ((physicsFlags & PhysicsDescriptionFlag.AnimationFrame) != 0)
{
if (body.Length - pos < 4) return null;
pos += 4;
}
ServerPosition? position = null;
if ((physicsFlags & PhysicsDescriptionFlag.Position) != 0)
{
if (body.Length - pos < 32) return null;
position = new ServerPosition(
LandblockId: BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(pos + 0)),
PositionX: BinaryPrimitives.ReadSingleLittleEndian(body.Slice(pos + 4)),
PositionY: BinaryPrimitives.ReadSingleLittleEndian(body.Slice(pos + 8)),
PositionZ: BinaryPrimitives.ReadSingleLittleEndian(body.Slice(pos + 12)),
RotationW: BinaryPrimitives.ReadSingleLittleEndian(body.Slice(pos + 16)),
RotationX: BinaryPrimitives.ReadSingleLittleEndian(body.Slice(pos + 20)),
RotationY: BinaryPrimitives.ReadSingleLittleEndian(body.Slice(pos + 24)),
RotationZ: BinaryPrimitives.ReadSingleLittleEndian(body.Slice(pos + 28)));
pos += 32;
}
if ((physicsFlags & PhysicsDescriptionFlag.MTable) != 0)
{
if (body.Length - pos < 4) return null;
pos += 4;
}
if ((physicsFlags & PhysicsDescriptionFlag.STable) != 0)
{
if (body.Length - pos < 4) return null;
pos += 4;
}
if ((physicsFlags & PhysicsDescriptionFlag.PeTable) != 0)
{
if (body.Length - pos < 4) return null;
pos += 4;
}
uint? setupTableId = null;
if ((physicsFlags & PhysicsDescriptionFlag.CSetup) != 0)
{
if (body.Length - pos < 4) return null;
setupTableId = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(pos));
pos += 4;
}
// Stop here — further fields (Parent, Children, ObjScale, Friction,
// Elasticity, Translucency, Velocity, Acceleration, Omega, DefaultScript,
// timestamps, weenie header, ...) aren't needed to render the entity.
return new Parsed(guid, position, setupTableId);
}
catch
{
return null;
}
}
private static uint ReadU32(ReadOnlySpan<byte> source, ref int pos)
{
if (source.Length - pos < 4) throw new FormatException("truncated u32");
uint v = BinaryPrimitives.ReadUInt32LittleEndian(source.Slice(pos));
pos += 4;
return v;
}
/// <summary>
/// Read a PackedDword from the stream. Format:
/// <list type="bullet">
/// <item>u16 first. If the top bit (0x8000) is clear, the u16 IS the value (0..0x7FFF).</item>
/// <item>Otherwise, read another u16 and combine: the full 32-bit value
/// is <c>((lowHalfTopBitStripped) &lt;&lt; 16) | highHalfFromNextU16</c>.</item>
/// </list>
/// Ported from ACE's Extensions.WritePackedDword: for values ≤ 32767, emitted as
/// u16; for larger, emitted as <c>(value &lt;&lt; 16) | ((value &gt;&gt; 16) | 0x8000)</c>
/// written as a little-endian u32. The reader is the inverse — sees the high-
/// bit marker in the first u16, then reads the second u16.
/// </summary>
private static uint ReadPackedDword(ReadOnlySpan<byte> source, ref int pos)
{
if (source.Length - pos < 2) throw new FormatException("truncated PackedDword");
ushort first = BinaryPrimitives.ReadUInt16LittleEndian(source.Slice(pos));
pos += 2;
if ((first & 0x8000) == 0)
return first;
// Extended form: first holds the HIGH 16 bits with top bit as marker,
// next u16 holds the LOW 16 bits. Strip the marker bit from the high half.
if (source.Length - pos < 2) throw new FormatException("truncated PackedDword ext");
ushort second = BinaryPrimitives.ReadUInt16LittleEndian(source.Slice(pos));
pos += 2;
uint high = (uint)(first & 0x7FFF);
return (high << 16) | second;
}
private static void AlignTo4(ref int pos)
{
int padding = (4 - (pos & 3)) & 3;
pos += padding;
}
}

38
tests/AcDream.Core.Net.Tests/LiveHandshakeTests.cs
View file

@ -406,10 +406,14 @@ public class LiveHandshakeTests
CharacterEnterWorld.BuildEnterWorldBody(chosen.Id, user),
$"CharacterEnterWorld(guid=0x{chosen.Id:X8})");
// ---- Step 8: receive the CreateObject flood. ----
// ---- Step 8: receive the CreateObject flood + parse bodies. ----
int totalMessages = 0;
int createObjectCount = 0;
int createObjectParsed = 0;
int createObjectWithPosition = 0;
int createObjectWithSetup = 0;
var seenOpcodes = new HashSet<uint>();
var parsedCreateObjects = new List<CreateObject.Parsed>();
var d8 = DateTime.UtcNow + TimeSpan.FromSeconds(10);
while (DateTime.UtcNow < d8)
{
@ -428,19 +432,41 @@ public class LiveHandshakeTests
uint op = BinaryPrimitives.ReadUInt32LittleEndian(body);
seenOpcodes.Add(op);
totalMessages++;
if (op == 0xF745u) // CreateObject
if (op == CreateObject.Opcode)
{
createObjectCount++;
var parsed = CreateObject.TryParse(body);
if (parsed is not null)
{
createObjectParsed++;
parsedCreateObjects.Add(parsed.Value);
if (parsed.Value.Position is not null) createObjectWithPosition++;
if (parsed.Value.SetupTableId is not null) createObjectWithSetup++;
}
}
}
}
Console.WriteLine($"[live] step 8 summary: {totalMessages} GameMessages assembled, " +
$"{createObjectCount} CreateObject");
$"{createObjectCount} CreateObject, " +
$"{createObjectParsed} parsed, " +
$"{createObjectWithPosition} w/position, " +
$"{createObjectWithSetup} w/setup");
Console.WriteLine("[live] unique opcodes seen: " +
string.Join(", ", seenOpcodes.Select(o => $"0x{o:X8}")));
// MILESTONE: if we got at least one CreateObject, the server considers
// us logged into the world. That's the Phase 4.7 win condition.
// Dump the first 10 parsed CreateObjects so we can eyeball whether
// the positions match Holtburg and the setup ids look like dat ids.
foreach (var co in parsedCreateObjects.Take(10))
{
string posStr = co.Position is { } p
? $"lb=0x{p.LandblockId:X8} xyz=({p.PositionX:F2},{p.PositionY:F2},{p.PositionZ:F2})"
: "no position";
string setupStr = co.SetupTableId is { } s ? $"setup=0x{s:X8}" : "no setup";
Console.WriteLine($"[live] CreateObject guid=0x{co.Guid:X8} {posStr} {setupStr}");
}
Assert.True(createObjectCount > 0,
$"Expected at least one CreateObject message post-login, got {createObjectCount}");
$"Expected at least one CreateObject post-login, got {createObjectCount}");
}
}