Eliminate RepeatedPtrFieldBase::Rep::allocated_size: fix slow extending
#23938
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−122
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…ding Fixes the slowdown in the field mutations caused by `memset`ting newly added elements to nulls in `RepeatedPtrField::InternalExtend()`: * Instead of `memset`ting the entire new array, sets only one or at most two sentinel elements to nulls. * The first sentinel immediately follows the last allocated (non-null) element, if there is an unallocated gap due to intentional overallocating in `InternalExtend()`. This is used to terminate several for-loops that previously relied on `allocated_size()`, and to reimplement `allocated_size()` (now `AllocatedSize()` because it's now slower and no longer trivial) for just a couple remaining places that still use the value. * The second sentinel is always the last unallocated element, just before `Capacity()`, also when there is an unallocated gap and possibly coinciding with the other sentinel if the gap is just 1 element. This sentinel is used to determine if the fuild has unallocated elements. * The methods that previously incremented or decremented `allocated_size()` now move the sentinels in the appropriate direction. PiperOrigin-RevId: 814520734
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Eliminate
RepeatedPtrFieldBase::Rep::allocated_size: fix slow extendingFixes the slowdown in the field mutations caused by
memsetting newly added elements to nulls inRepeatedPtrField::InternalExtend():memsetting the entire new array, sets only one or at most two sentinel elements to nulls.InternalExtend(). This is used to terminate several for-loops that previously relied onallocated_size(), and to reimplementallocated_size()(nowAllocatedSize()because it's now slower and no longer trivial) for just a couple remaining places that still use the value.Capacity(), also when there is an unallocated gap and possibly coinciding with the other sentinel if the gap is just 1 element. This sentinel is used to determine if the fuild has unallocated elements.allocated_size()now move the sentinels in the appropriate direction.