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Fix overflow bug in SizeOfEquivalentValueRange #169

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Fix overflow bug in SizeOfEquivalentValueRange #169

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21 changes: 21 additions & 0 deletions HdrHistogram.UnitTests/HistogramTestBase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -546,6 +546,27 @@ public void GetPercentileAtOrBelowValue_NegativeValue_ReturnsZero()
histogram.GetPercentileAtOrBelowValue(long.MinValue).Should().Be(0.0);
}

[Fact]
public void SizeOfEquivalentValueRangeDoesNotOverflow()
{
var histogram = Create(long.MaxValue, DefaultSignificantFigures);

for (int i = 0; i < 8; i++)
{
histogram.RecordValue(1);
}

histogram.RecordValue((1L << 41) + 1);

histogram.RecordValue((1L << 50) + 1);

var p90 = histogram.GetValueAtPercentile(90);

p90.Should().BeGreaterThan((1L << 41) + 1);
histogram.SizeOfEquivalentValueRange((1L << 41) + 1).Should().Be((1L << 31));
p90.Should().Be((1L << 41) + (1L << 31) - 1);
}

private void CreateAndAdd(HistogramBase source)
{
source.RecordValueWithCount(1, 100);
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2 changes: 1 addition & 1 deletion HdrHistogram/HistogramBase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -355,7 +355,7 @@ public long SizeOfEquivalentValueRange(long value)
bucketIndex++;
}

var distanceToNextValue = 1 << (_unitMagnitude + bucketIndex);
var distanceToNextValue = 1L << (_unitMagnitude + bucketIndex);
return distanceToNextValue;
}

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