[shared] Add TagWriter implementation (#5476)

OpenTelemetry.sln

@@ -348,6 +348,13 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Configuration", "Configurat
  src\Shared\Configuration\OpenTelemetryConfigurationExtensions.cs = src\Shared\Configuration\OpenTelemetryConfigurationExtensions.cs
  EndProjectSection
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "TagWriter", "TagWriter", "{993E65E5-E71B-40FD-871C-60A9EBD59724}"
+ ProjectSection(SolutionItems) = preProject
+ src\Shared\TagWriter\ArrayTagWriter.cs = src\Shared\TagWriter\ArrayTagWriter.cs
+ src\Shared\TagWriter\JsonStringArrayTagWriter.cs = src\Shared\TagWriter\JsonStringArrayTagWriter.cs
+ src\Shared\TagWriter\TagWriter.cs = src\Shared\TagWriter\TagWriter.cs
+ EndProjectSection
+EndProject
 Global
  GlobalSection(SolutionConfigurationPlatforms) = preSolution
  Debug|Any CPU = Debug|Any CPU
@@ -694,6 +701,7 @@ Global
  {7BE494FC-4B0D-4340-A62A-9C9F3E7389FE} = {A115CE4C-71A8-4B95-96A5-C1DF46FD94C2}
  {19545B37-8518-4BDD-AD49-00C031FB3C2A} = {3862190B-E2C5-418E-AFDC-DB281FB5C705}
  {87A20A76-D524-4AAC-AF92-8725BFED0415} = {A49299FB-C5CD-4E0E-B7E1-B7867BBD67CC}
+ {993E65E5-E71B-40FD-871C-60A9EBD59724} = {A49299FB-C5CD-4E0E-B7E1-B7867BBD67CC}
  EndGlobalSection
  GlobalSection(ExtensibilityGlobals) = postSolution
  SolutionGuid = {55639B5C-0770-4A22-AB56-859604650521}

src/Shared/TagWriter/ArrayTagWriter.cs

@@ -0,0 +1,24 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#nullable enable
+
+namespace OpenTelemetry.Internal;
+
+internal abstract class ArrayTagWriter<TArrayState>
+ where TArrayState : notnull
+{
+ public abstract TArrayState BeginWriteArray();
+
+ public abstract void WriteNullValue(ref TArrayState state);
+
+ public abstract void WriteIntegralValue(ref TArrayState state, long value);
+
+ public abstract void WriteFloatingPointValue(ref TArrayState state, double value);
+
+ public abstract void WriteBooleanValue(ref TArrayState state, bool value);
+
+ public abstract void WriteStringValue(ref TArrayState state, string value);
+
+ public abstract void EndWriteArray(ref TArrayState state);
+}

src/Shared/TagWriter/JsonStringArrayTagWriter.cs

@@ -0,0 +1,99 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#nullable enable
+
+using System.Diagnostics;
+using System.Text.Json;
+
+namespace OpenTelemetry.Internal;
+
+internal abstract class JsonStringArrayTagWriter<TTagState> : TagWriter<TTagState, JsonStringArrayTagWriter<TTagState>.JsonArrayTagWriterState>
+ where TTagState : notnull
+{
+ protected JsonStringArrayTagWriter()
+ : base(new JsonArrayTagWriter())
+ {
+ }
+
+ protected sealed override void WriteArrayTag(ref TTagState writer, string key, ref JsonArrayTagWriterState array)
+ {
+ var result = array.Stream.TryGetBuffer(out var buffer);
+
+ Debug.Assert(result, "result was false");
+
+ this.WriteArrayTag(ref writer, key, buffer);
+ }
+
+ protected abstract void WriteArrayTag(ref TTagState writer, string key, ArraySegment<byte> arrayUtf8JsonBytes);
+
+ internal readonly struct JsonArrayTagWriterState(MemoryStream stream, Utf8JsonWriter writer)
+ {
+ public MemoryStream Stream { get; } = stream;
+
+ public Utf8JsonWriter Writer { get; } = writer;
+ }
+
+ internal sealed class JsonArrayTagWriter : ArrayTagWriter<JsonArrayTagWriterState>
+ {
+ [ThreadStatic]
+ private static MemoryStream? threadStream;
+
+ [ThreadStatic]
+ private static Utf8JsonWriter? threadWriter;
+
+ public override JsonArrayTagWriterState BeginWriteArray()
+ {
+ var state = EnsureWriter();
+ state.Writer.WriteStartArray();
+ return state;
+ }
+
+ public override void EndWriteArray(ref JsonArrayTagWriterState state)
+ {
+ state.Writer.WriteEndArray();
+ state.Writer.Flush();
+ }
+
+ public override void WriteBooleanValue(ref JsonArrayTagWriterState state, bool value)
+ {
+ state.Writer.WriteBooleanValue(value);
+ }
+
+ public override void WriteFloatingPointValue(ref JsonArrayTagWriterState state, double value)
+ {
+ state.Writer.WriteNumberValue(value);
+ }
+
+ public override void WriteIntegralValue(ref JsonArrayTagWriterState state, long value)
+ {
+ state.Writer.WriteNumberValue(value);
+ }
+
+ public override void WriteNullValue(ref JsonArrayTagWriterState state)
+ {
+ state.Writer.WriteNullValue();
+ }
+
+ public override void WriteStringValue(ref JsonArrayTagWriterState state, string value)
+ {
+ state.Writer.WriteStringValue(value);
+ }
+
+ private static JsonArrayTagWriterState EnsureWriter()
+ {
+ if (threadStream == null)
+ {
+ threadStream = new MemoryStream();
+ threadWriter = new Utf8JsonWriter(threadStream);
+ return new(threadStream, threadWriter);
+ }
+ else
+ {
+ threadStream.SetLength(0);
+ threadWriter!.Reset(threadStream);
+ return new(threadStream, threadWriter);
+ }
+ }
+ }
+}