Lots of high performance goodness. Implement function taking Span as a parameter and it can be called with an array, stackalloc'd memory, native memory with a s

Lots of high performance goodness. Implement function taking Span as a parameter and it can be called with an array, stackalloc'd memory, native memory with a single implementation and in a type safe way. However, an item I think is often overlooked is the safety: ArraySegment or the triple: "array, offset, length" when used; only provides a suggestion to the called function - it still has full access to the array and can happily read and write out of offset->length portion of the array. Span only allows access to the window, so the called function can't operate out of its permitted bounds. Further to this ReadOnlySpan finally gives read-only array elements; so rather than having to a defensive copy and passing out a newly allocated array; you can pass out (or in) a ReadOnlySpan