Joseph Doherty
43 lines
1.8 KiB
C#
43 lines
1.8 KiB
C#
using System;
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using System.Security.Cryptography;
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using System.Text;
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namespace ZB.MOM.WW.MxGateway.Worker.MxAccess;
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/// <summary>
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/// Derives a deterministic synthetic <see cref="Guid"/> from an alarm
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/// reference for the subtag-provider fallback path, which has no native
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/// MxAccess alarm GUID. Hashing the reference yields a stable identity so
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/// repeated transitions for the same alarm reference correlate downstream
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/// (acknowledge, snapshot, OPC UA mapping) without an alarmmgr-supplied GUID.
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/// </summary>
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public static class SyntheticAlarmGuid
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{
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/// <summary>
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/// Produces a stable <see cref="Guid"/> for the given alarm reference.
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/// The same reference always maps to the same GUID; distinct references
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/// map to distinct GUIDs with overwhelming probability.
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/// </summary>
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/// <param name="reference">
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/// The fully-qualified alarm reference (for example
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/// <c>"Galaxy!Area.Tag.HiHi"</c>). Treated as UTF-8 bytes.
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/// </param>
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/// <returns>A deterministic, non-empty GUID derived from the reference.</returns>
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/// <exception cref="ArgumentNullException">
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/// Thrown when <paramref name="reference"/> is <see langword="null"/>.
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/// </exception>
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public static Guid ForReference(string reference)
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{
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if (reference is null) throw new ArgumentNullException(nameof(reference));
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byte[] bytes = Encoding.UTF8.GetBytes(reference);
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// MD5 is used purely for a stable, non-cryptographic identity mapping
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// (reference -> 16-byte GUID), never for security. Its 128-bit output
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// fits a GUID exactly, which is why it is preferred here.
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using MD5 md5 = MD5.Create();
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byte[] hash = md5.ComputeHash(bytes);
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return new Guid(hash);
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}
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}
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