Lance Parker cbf157f924 [stdlib]Unify String hashing implementation (#14921) ...

* Add partial range subscripts to _UnmanagedOpaqueString

* Use SipHash13+_NormalizedCodeUnitIterator for String hashes on all platforms

* Remove unecessary collation algorithm shims

* Pass the buffer to the SipHasher for ASCII

* Hash the ascii parts of UTF16 strings the same way we hash pure ascii strings

* De-dupe some code that can be shared between _UnmanagedOpaqueString and _UnmanagedString<UInt16>

* ASCII strings now hash consistently for in hashASCII() and hashUTF16()

* Fix zalgo comparison regression

* Use hasher

* Fix crash when appending to an empty _FixedArray

* Compact ASCII characters into a single UInt64 for hashing

* String: Switch to _hash(into:)-based hashing

This should speed up String hashing quite a bit, as doing it through hashValue involves two rounds of SipHash nested in each other.

* Remove obsolete workaround for ARC traffic

* Ditch _FixedArray<UInt8> in favor of _UIntBuffer<UInt64, UInt8>

* Bad rebase remnants

* Fix failing benchmarks

* michael's feedback

* clarify the comment about nul-terminated string hashes

2018-03-17 22:13:37 -07:00

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