ALTREP-backed zero-copy vectors for shared memory.
Details
These functions create ALTREP (Alternative Representation) vectors that are backed by shared memory segments. The key benefits are:
Zero-copy subsetting: Contiguous subsets return views into the same shared memory, not copies.
Diagnostics: Track when data pointers are accessed or when vectors are materialized (copied to standard R vectors).
Read-only protection: Optionally prevent write access to protect shared data.
Supported types: integer, double/numeric, logical, raw.