mirror of
https://github.com/OPCFoundation/UA-.NETStandard.git
synced 2026-10-19 15:22:15 +08:00
Marc Schier
889572472f
Convert `DataValue` from a mutable reference type (`class`) to a `readonly struct` to eliminate per-allocation GC pressure on every attribute read, subscription publish, and history sample. ### Key API changes (user-visible) | Before | After | Pattern | |---|---|---| | `class DataValue` | `readonly struct DataValue : INullable` | Foundation | | `Equals(DataValue?)` / `operator ==(DataValue?, DataValue?)` | `Equals(DataValue)` / `operator ==(DataValue, DataValue)` | Value semantics | | `IEncoder.WriteDataValue(string?, DataValue?)` | `IEncoder.WriteDataValue(string?, DataValue)` | Non-nullable wire API | | `IDecoder.ReadDataValue(...) -> DataValue?` | `IDecoder.ReadDataValue(...) -> DataValue` | Same | | `IDataChangeMonitoredItemQueue.PeekLast/Oldest()` | `TryPeekLastValue/Oldest(out DataValue)` | TryGet pattern | | `IAggregateCalculator.GetProcessedValue(bool)` | `TryGetProcessedValue(bool, out DataValue)` | Same | | `IUaPubSubDataStore.ReadPublishedDataItem(...)` | `TryReadPublishedDataItem(NodeId, uint, out DataValue)` | Same | | `Dictionary<uint, DataValue?>` (NodeCacheContext) | `Dictionary<uint, DataValue>` | Default + IsNull | | `IHistoryDataSource.FirstRaw/NextRaw` | `TryFirstRaw/TryNextRaw(out DataValue)` | TryGet pattern | | `NodeState.ReadAttribute(... DataValue)` | `NodeState.ReadAttribute(... ref DataValue)` | Sync mutation via ref | | `NodeState.ReadAttributeAsync(... DataValue)` | `NodeState.ReadAttributeAsync(...) -> ValueTask<(ServiceResult, DataValue)>` | Async return tuple | | `obj as DataValue` (heterogeneous Dictionary<string, object>) | `obj is DataValue dv ? dv : default(DataValue)` | Safe struct cast | | `Assert.That(dv, Is.Not.Null)` (tests) | `Assert.That(dv.IsNull, Is.False)` | Struct test pattern | | `[Obsolete] Value` setter, all property setters | Removed; use ctor or `With*()` | Immutability | | `[DataContract]` + `[DataMember]` | Removed; surrogate via `SerializableDataValue` + `DataValueSurrogateProvider` | Serialization | ### Wire format Wire format is **byte-identical** to the previous class-based implementation across binary / JSON / XML encoders. Default DataValue (`.IsNull == true`) is treated as the equivalent of the old null reference (writes JSON `null`, binary `byte 0`, XML omitted element). ### Why TryGet pattern (instead of leaving `DataValue?`) For methods that previously returned `DataValue?` to signal "no value available" (queue peek, aggregate result, data store lookup, history navigation), the conversion to `bool TryGet(out DataValue)` matches BCL conventions (`Dictionary.TryGetValue`, `Queue.TryPeek`, `Int32.TryParse`) and gives the caller an explicit "may be absent" affordance without `Nullable<DataValue>` overhead. ### Breaking changes summary - `DataValue` is now a `readonly struct` - boxing/unboxing semantics change for callers using `object`-typed APIs. - `IEncoder.WriteDataValue` / `IDecoder.ReadDataValue` / `ReadDataValueArray` interface signatures lose the `Nullable` wrapper. - `IDataChangeMonitoredItemQueue.PeekLastValue` / `PeekOldestValue` -> `TryPeekLastValue` / `TryPeekOldestValue` (out parameter). - `IAggregateCalculator.GetProcessedValue` -> `TryGetProcessedValue` (out parameter). - `IUaPubSubDataStore.ReadPublishedDataItem` -> `TryReadPublishedDataItem` (out parameter). - `NodeState.ReadAttribute` takes `ref DataValue`; `ReadAttributeAsync` returns `ValueTask<(ServiceResult, DataValue)>`. - `DataValue` property setters removed (use constructor + `With*` mutators).
85 lines
2.9 KiB
C#
85 lines
2.9 KiB
C#
/* ========================================================================
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* Copyright (c) 2005-2025 The OPC Foundation, Inc. All rights reserved.
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*
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* OPC Foundation MIT License 1.00
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*
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* The complete license agreement can be found here:
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* http://opcfoundation.org/License/MIT/1.00/
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* ======================================================================*/
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using System;
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namespace Opc.Ua.PubSub.PublishedData
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{
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/// <summary>
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/// Base class for a DataSet field
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/// </summary>
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public class Field : ICloneable
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{
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/// <summary>
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/// Get/Set Value
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/// </summary>
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public DataValue Value { get; set; }
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/// <summary>
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/// Get/Set Target NodeId
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/// </summary>
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public NodeId TargetNodeId { get; set; }
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/// <summary>
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/// Get/Set target attribute
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/// </summary>
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public uint TargetAttribute { get; set; }
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/// <summary>
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/// Get configured <see cref="FieldMetaData"/> object for this <see cref="Field"/> instance.
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/// </summary>
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public FieldMetaData? FieldMetaData { get; internal set; }
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/// <inheritdoc/>
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public virtual object Clone()
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{
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return MemberwiseClone();
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}
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/// <summary>
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/// Create a deep copy of current DataSet
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/// </summary>
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public new object MemberwiseClone()
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{
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var copy = base.MemberwiseClone() as Field;
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if (!Value.IsNull && copy != null)
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{
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copy.Value = Value.Copy();
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}
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if (FieldMetaData != null && copy != null)
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{
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copy.FieldMetaData = CoreUtils.Clone(FieldMetaData);
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}
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// base.MemberwiseClone() always returns a non-null Field instance.
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return copy!;
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}
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}
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}
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