UUIDv47: UUIDv7-in / UUIDv4-out (SipHash-masked timestamp)

uuidv47 is a header-only C library (C89, no dependencies) that stores sortable UUIDv7 values in a database while emitting UUIDv4-looking identifiers at the API boundary. It XOR-masks the 48-bit UUIDv7 timestamp with a keyed SipHash-2-4 stream derived from the UUID's random bits, so the mapping is deterministic and exactly invertible when the key is known. The project also ships an optional PostgreSQL extension, Go, JavaScript, C#, Ruby, PHP, Python and Rust ports, and is released under the MIT license by Stateless Limited.