LabelInstructionInterpretter.cs

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using System.Collections.Concurrent;
using System.Collections.Generic;
 
namespace System.Diagnostics.Metrics;
 
internal class LabelInstructionInterpretter<TObjectSequence, TAggregator> where TObjectSequence : struct, IObjectSequence, IEquatable<TObjectSequence> where TAggregator : Aggregator
{
    private int _expectedLabelCount;
 
    private LabelInstruction[] _instructions;
 
    private ConcurrentDictionary<TObjectSequence, TAggregator> _valuesDict;
 
    private Func<TObjectSequence, TAggregator> _createAggregator;
 
    public LabelInstructionInterpretter(int expectedLabelCount, LabelInstruction[] instructions, ConcurrentDictionary<TObjectSequence, TAggregator> valuesDict, Func<TAggregator> createAggregator)
    {
        _expectedLabelCount = expectedLabelCount;
        _instructions = instructions;
        _valuesDict = valuesDict;
        _createAggregator = (TObjectSequence _) => createAggregator();
    }
 
    public bool GetAggregator(ReadOnlySpan<KeyValuePair<string, object>> labels, out TAggregator aggregator)
    {
        aggregator = null;
        if (labels.Length != _expectedLabelCount)
        {
            return false;
        }
        TObjectSequence val = default(TObjectSequence);
        if (val is ObjectSequenceMany)
        {
            val = (TObjectSequence)(object)new ObjectSequenceMany(new object[_expectedLabelCount]);
        }
        Span<object> span = val.AsSpan();
        for (int i = 0; i < _instructions.Length; i++)
        {
            LabelInstruction labelInstruction = _instructions[i];
            if (labelInstruction.LabelName != labels[labelInstruction.SourceIndex].Key)
            {
                return false;
            }
            span[i] = labels[labelInstruction.SourceIndex].Value;
        }
        if (!_valuesDict.TryGetValue(val, out aggregator))
        {
            aggregator = _createAggregator(val);
            if (aggregator == null)
            {
                return true;
            }
            aggregator = _valuesDict.GetOrAdd(val, aggregator);
        }
        return true;
    }
}