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M3 R3.2: HistorianHistoricalWriteProtocol — the "ON" AddStreamValues serializer (golden-validated)

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Managed serializer for the historical-write "ON" buffer, byte-for-byte matching the live capture
(WcfHistoricalWriteProtocolTests golden-tests the exact 56-byte native buffer). Layout: "ON"(0x4E4F)
+ count + lengths + 16B tag GUID + sample FILETIME + u16 quality(192) + 4B descriptor + received
FILETIME + value. Value encoding (Float, captured): an 8-byte slot = u32(0) + float32(value) — the
4-byte float in the high dword, NOT a double. The 16B tag GUID is the per-tag GUID the SDK already
parses as ParseTagInfoRecord's "typeId" (confirmed: it appears at offset 8 of GetTagInfosFromName's
response = where typeId is read, and in EnsureTags' response + the "ON" buffer).

Only the Float encoding is captured; other types rejected until captured. Next: gRPC orchestrator
(write-enabled session -> EnsureTags -> resolve tag GUID -> AddStreamValues) + public
AddHistoricalValuesAsync + live write/read-back.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B6mcaT2PjRFKcogzp9UkfC
This commit is contained in:
Joseph Doherty
2026-06-21 21:17:14 -04:00
parent 0e78d638d0
commit 85f0c2f0fa
2 changed files with 142 additions and 0 deletions
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src/AVEVA.Historian.Client/Wcf/HistorianHistoricalWriteProtocol.cs
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using System.Buffers.Binary;
namespace AVEVA.Historian.Client.Wcf;
/// <remarks>
/// Serializer for the M3 historical (non-streamed original / backfill) value write — the
/// <c>HistoryService.AddStreamValues</c> <c>values</c> buffer. Decoded byte-for-byte from a live
/// capture of the native 2023 R2 gRPC client driving
/// <c>HistorianAccess.AddNonStreamedValue → SendValues</c> against a sandbox tag (see
/// <c>docs/plans/revision-write-path.md</c> §"R3.1 CAPTURED"). The native non-streamed write does
/// NOT use the TransactionService <c>AddNonStreamValues</c> path the static decompile suggested — it
/// rides <c>HistoryService.AddStreamValues</c> with an "ON" storage-sample buffer, the analog sibling
/// of the AddS2 "OS" event buffer (<see cref="HistorianEventWriteProtocol"/>).
///
/// <code>
/// values buffer (single analog sample):
/// 0x00 UInt16 0x4E4F // "ON" signature
/// 0x02 UInt16 sampleCount = 1
/// 0x04 UInt32 10 + valueBlob.Length // total buffer length
/// 0x08 UInt16 valueBlob.Length
/// 0x0A valueBlob (46 bytes for one analog double):
/// +0x00 GUID tag GUID (the per-tag GUID = the value ParseTagInfoRecord reads as "typeId")
/// +0x10 Int64 sample FILETIME (UTC — the VTQ value timestamp)
/// +0x18 UInt16 OpcQuality = 192 (good)
/// +0x1A 4 bytes analog value descriptor (constant for the Float path: C0 10 01 00)
/// +0x1E Int64 received/version FILETIME (UTC)
/// +0x26 UInt32 0 // value high dword (zero for a 4-byte Float)
/// +0x2A Float32 value // the Float value sits in the high half of the 8-byte slot
/// </code>
///
/// Captured against a Float tag: the value occupies an 8-byte slot as <c>u32(0) + float32(value)</c>
/// (the 4-byte IEEE-754 float in the high dword, NOT an 8-byte double). Only the Float encoding is
/// captured; Double/Int/string tag types use a different descriptor + value width and are rejected
/// until captured.
/// </remarks>
internal static class HistorianHistoricalWriteProtocol
{
public const ushort BufferSignature = 0x4E4F; // "ON"
public const ushort OpcQualityGood = 192;
// Captured constant for the analog double value path. The other observed quality/descriptor
// bytes in the AddS2 "OS" buffer are event-specific; here this 4-byte block sits between the
// quality and the received-time FILETIME and was constant across captured analog writes.
private static readonly byte[] AnalogDoubleDescriptor = [0xC0, 0x10, 0x01, 0x00];
private const int ValueBlobLength = 16 + 8 + 2 + 4 + 8 + 8; // 46
/// <summary>
/// Builds the <c>AddStreamValues</c> <c>values</c> buffer for a single analog historical sample.
/// <paramref name="tagGuid"/> is the per-tag GUID (from the gRPC tag-info read), and
/// <paramref name="receivedTimeUtc"/> is the storage/received timestamp the orchestrator stamps.
/// </summary>
public static byte[] SerializeAddStreamValuesBuffer(
Guid tagGuid,
DateTime sampleTimeUtc,
double value,
DateTime receivedTimeUtc,
ushort quality = OpcQualityGood)
{
byte[] valueBlob = SerializeValueBlob(tagGuid, sampleTimeUtc, value, receivedTimeUtc, quality);
byte[] buffer = new byte[10 + valueBlob.Length];
BinaryPrimitives.WriteUInt16LittleEndian(buffer.AsSpan(0, 2), BufferSignature);
BinaryPrimitives.WriteUInt16LittleEndian(buffer.AsSpan(2, 2), 1); // sampleCount
BinaryPrimitives.WriteUInt32LittleEndian(buffer.AsSpan(4, 4), checked((uint)(10 + valueBlob.Length)));
BinaryPrimitives.WriteUInt16LittleEndian(buffer.AsSpan(8, 2), checked((ushort)valueBlob.Length));
valueBlob.CopyTo(buffer.AsSpan(10));
return buffer;
}
private static byte[] SerializeValueBlob(
Guid tagGuid,
DateTime sampleTimeUtc,
double value,
DateTime receivedTimeUtc,
ushort quality)
{
byte[] blob = new byte[ValueBlobLength];
Span<byte> span = blob;
tagGuid.ToByteArray().CopyTo(span[..16]);
BinaryPrimitives.WriteInt64LittleEndian(span.Slice(16, 8), ToFileTime(sampleTimeUtc));
BinaryPrimitives.WriteUInt16LittleEndian(span.Slice(24, 2), quality);
AnalogDoubleDescriptor.CopyTo(span.Slice(26, 4));
BinaryPrimitives.WriteInt64LittleEndian(span.Slice(30, 8), ToFileTime(receivedTimeUtc));
// The value sits in an 8-byte slot as u32(0) + float32(value): the captured Float tag stored
// a 4-byte IEEE-754 float in the high dword, not an 8-byte double.
BinaryPrimitives.WriteUInt32LittleEndian(span.Slice(38, 4), 0);
BinaryPrimitives.WriteSingleLittleEndian(span.Slice(42, 4), (float)value);
return blob;
}
private static long ToFileTime(DateTime value)
{
DateTime utc = value.Kind == DateTimeKind.Utc ? value : value.ToUniversalTime();
return utc.ToFileTimeUtc();
}
}