e928c5dd02
Decode headers, optional fields, fragments, and single-fragment messages directly over pooled datagrams. Copy only fragment state that crosses a datagram lifetime, preserve synchronous dispatch and ACK ordering, and lock the path to the owned decoder with differential and zero-allocation tests.
69 lines
2.4 KiB
C#
69 lines
2.4 KiB
C#
using System;
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using System.Buffers.Binary;
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namespace AcDream.Core.Net.Messages;
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/// <summary>
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/// Parsed header of a retail AC <c>0xF7B0</c> GameEvent envelope (S→C).
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///
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/// <para>
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/// Wire layout
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/// (references/ACE/Source/ACE.Server/Network/GameEvent/GameEventMessage.cs):
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/// <code>
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/// u32 0xF7B0 // GameMessage opcode (GameEvent envelope)
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/// u32 guid // session's player guid (0 if none yet)
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/// u32 gameEventSequence // per-session, incremented by server
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/// u32 eventType // GameEventType sub-opcode (94 values)
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/// <payload> // variable; type-dispatched
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/// </code>
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/// </para>
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///
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/// <para>
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/// Payload is returned as a <see cref="ReadOnlyMemory{T}"/> view into the
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/// original message body — no copy. Per-event parsers slice from this.
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/// </para>
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/// </summary>
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public readonly record struct GameEventEnvelope(
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uint PlayerGuid,
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uint Sequence,
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GameEventType EventType,
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ReadOnlyMemory<byte> Payload)
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{
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/// <summary>GameMessage opcode of the outer envelope.</summary>
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public const uint Opcode = 0xF7B0u;
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/// <summary>Header size (4×u32 = 16 bytes before payload).</summary>
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public const int HeaderSize = 16;
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/// <summary>
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/// Parse a raw 0xF7B0 GameMessage body into the header + payload view.
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/// Returns null if the body is shorter than the header or the outer
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/// opcode doesn't match.
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/// </summary>
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public static GameEventEnvelope? TryParse(byte[] body)
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{
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ArgumentNullException.ThrowIfNull(body);
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return TryParseBorrowed(body);
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}
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/// <summary>
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/// Internal receive-path parser. The returned payload borrows
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/// <paramref name="body"/> and must not escape synchronous dispatch.
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/// </summary>
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internal static GameEventEnvelope? TryParseBorrowed(
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ReadOnlyMemory<byte> body)
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{
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if (body.Length < HeaderSize) return null;
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ReadOnlySpan<byte> span = body.Span;
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uint outer = BinaryPrimitives.ReadUInt32LittleEndian(span);
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if (outer != Opcode) return null;
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uint guid = BinaryPrimitives.ReadUInt32LittleEndian(span.Slice(4));
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uint sequence = BinaryPrimitives.ReadUInt32LittleEndian(span.Slice(8));
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uint eventType = BinaryPrimitives.ReadUInt32LittleEndian(span.Slice(12));
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ReadOnlyMemory<byte> payload = body.Slice(HeaderSize);
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return new GameEventEnvelope(guid, sequence, (GameEventType)eventType, payload);
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}
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}
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