Use spans for serialization

[paulomorgado]

Addresses #6543

Changes

Refactored serialization logic to use Span<byte> for buffer manipulation, improving performance, memory efficiency, and code readability. Updated method signatures to eliminate explicit writePosition management, replaced incremental write logic with consistent += operations, and streamlined encoding methods. Enhanced test coverage to validate edge cases and updated all test cases to align with the new implementation. Applied changes consistently across all serializers, ensuring backward compatibility and laying the groundwork for future optimizations. Improved error handling, debugging, and documentation for better maintainability and robustness.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.46%. Comparing base (3d0d972) to head (a67075d).
⚠️ Report is 5 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6544      +/-   ##
==========================================
- Coverage   86.70%   86.46%   -0.24%     
==========================================
  Files         258      258              
  Lines       11888    11648     -240     
==========================================
- Hits        10308    10072     -236     
+ Misses       1580     1576       -4     

Flag	Coverage Δ
unittests-UnstableCoreLibraries-Experimental	85.87% <ø> (+0.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ementation/Serializer/ProtobufOtlpLogSerializer.cs	99.08% <ø> (+0.59%)	⬆️
...ntation/Serializer/ProtobufOtlpMetricSerializer.cs	98.23% <ø> (-0.55%)	⬇️
...ation/Serializer/ProtobufOtlpResourceSerializer.cs	90.00% <ø> (-1.67%)	⬇️
...Implementation/Serializer/ProtobufOtlpTagWriter.cs	93.33% <ø> (-2.62%)	⬇️
...entation/Serializer/ProtobufOtlpTraceSerializer.cs	95.16% <ø> (+0.14%)	⬆️
...ol/Implementation/Serializer/ProtobufSerializer.cs	82.35% <ø> (-9.16%)	⬇️

[paulomorgado]

Hi @martincostello, @Kielek, can you help me here with the test failures?

[martincostello]

Put the blank line back, and the style analyser won't fail the build.

[Kielek]

In general, it is good practice to run local build in Release mode. Debug allows to compile with Warnings, Release is extremely strict.

[paulomorgado]

My bad! Sorry!

I have fixed the style errors, but I still have a test failing:

Failed OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests.OtlpAttributeTests.IntegralTypesSupported(value: [1, 2, 3]) [< 1 ms]
Error Message:
 Google.Protobuf.InvalidProtocolBufferException : Protocol message contained an invalid tag (zero).

I can't figure out how this is related to my changes.

Runing the tests in debug mode I get this:

 OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests.OtlpAttributeTests.IntegralTypesSupported(value: [1, 2, 3])
   Source: OtlpAttributeTests.cs line 56
   Duration: 7 ms

  Message: 
Microsoft.VisualStudio.TestPlatform.TestHost.DebugAssertException : Method Debug.Fail failed with 'bytesWritten did not match numberOfUtf8CharsInString
', and was translated to Microsoft.VisualStudio.TestPlatform.TestHost.DebugAssertException to avoid terminating the process hosting the test.

  Stack Trace: 
TestHostTraceListener.GetException(String message)
TestHostTraceListener.Fail(String message, String detailMessage)
TraceInternal.Fail(String message, String detailMessage)
Debug.Fail(String message, String detailMessage)
ProtobufOtlpTagWriter.TryWriteByteArrayTag(OtlpTagWriterState& state, String key, ReadOnlySpan`1 value) line 94
TagWriter`2.TryWriteTag(TTagState& state, String key, Object value, Nullable`1 tagValueMaxLength) line 70
TagWriter`2.TryWriteTag(TTagState& state, KeyValuePair`2 tag, Nullable`1 tagValueMaxLength) line 28
OtlpAttributeTests.TryTransformTag(KeyValuePair`2 tag, KeyValue& attribute) line 293
OtlpAttributeTests.IntegralTypesSupported(Object value) line 59

This happens because ProtobufOtlpTagWriter.TryWriteByteArrayTag is calling ProtobufSerializer.WriteStringWithTag with ProtobufOtlpCommonFieldNumberConstants.KeyValue_Key (1) for numberOfUtf8CharsInString with key as "key".

What am I missing here?

[github-actions]

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