We specialize `Optional<T>` for value types that inherently support some
kind of "empty" value or whose value range allow for a unlikely to be
useful sentinel value that can mean "empty", instead of the boolean flag
a regular Optional<T> needs to store. Because of padding, this often
means saving 4 to 8 bytes per instance.
By extending the new `SentinelOptional<T, Traits>`, these
specializations are significantly simplified to just having to define
what the sentinel value is, and how to identify a sentinel value.
This reverts commit c14173f651. We
should only annotate the minimum number of symbols that external
consumers actually use, so I am starting from scratch to do that
To prepare for an upcoming Utf16String, this migrates Utf16View to store
its data as a char16_t. Most function definitions are moved inline and
made constexpr.
This also adds a UDL to construct a Utf16View from a string literal:
auto string = u"hello"sv;
This let's us remove the NTTP Utf16View constructor, as we have found
that such constructors bloat binary size quite a bit.
For the slight cost of counting code points when converting between
encodings and a teeny bit of memory, this commit adds a fast path for
all-happy utf-16 substrings and code point operations.
This seems to be a significant chunk of time spent in many regex
benchmarks.
