Ensure HashSet.TrimExcess() does not change the count
#97989
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ghost
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Tagging subscribers to this area: @dotnet/area-system-collections Issue DetailsFix #97947.
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weltkante
approved these changes
Feb 5, 2024
stephentoub
approved these changes
Feb 5, 2024
This was referenced Feb 5, 2024
rhuijben
reviewed
Feb 6, 2024
| @@ -1055,7 +1049,7 @@ private void SetCapacity(int capacity) | |||
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| _count = capacity; | |||
| _count = count; | |||
| _freeCount = 0; | |||
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_freeCount = capacity - count; ?
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no, not necessarily
- _count is the number of "used" array slots (both free and actual hashset content)
- _freeCount is the number of free slots within the first _count array slots
So the slots starting from index _count to the end of the backing array are not counted in _freeCount. This is beneficial because you can skip this section when iterating the hashset, so you don't want to include them in the counters. Trimming moves all content to the front of the new array so you get the most out of this repacking by leaving _freeCount at zero.
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Fix #97947.