Infinite loop due to integer overflow

[codahale]

The following code never returns:

new Histogram(20000000, 100000000, 5);

It hangs here:

at org.HdrHistogram.AbstractHistogram.getBucketsNeededToCoverValue(AbstractHistogram.java:1440)
at org.HdrHistogram.AbstractHistogram.init(AbstractHistogram.java:189)
at org.HdrHistogram.AbstractHistogram.<init>(AbstractHistogram.java:152)
at org.HdrHistogram.Histogram.<init>(Histogram.java:139)

At line 1440, it sets trackableValue to (subBucketCount - 1) << unitMagnitude which is (262144 - 1) << 24, which overflows to -16777216. As a result the loop condition never returns true, because trackableValue eventually shifts down to 0.

[giltene]

The bug is in int / long conversion (shift left ops done on int instead of long before assignment).

Fixed with change dc4f9eb

Added test case with change 9c1b0b1

The test case also demonstrates the percentile roll-over point due to rounding (3 total values in histogram 83.33% will round down to 2nd value, 83.34% will round up to 3rd value).

[mikeb01]

Was broken in the C port too. Fix also applied in 9abf30a.