variabeletype

Variabeletype is a proposed or hypothetical data type used in discussions of type systems to represent values with variable structure and size. A variabeletype combines a fixed-size descriptor, including a type tag and a length field, with a payload that can vary in length or structure. This arrangement allows a single value to encode different data shapes, enabling flexible serialization, inter-process communication, and protocol design.

In practice, implementations resemble tagged unions or variants with heap-allocated payloads, sometimes using inline small payloads or length-prefixed blobs. Key properties include runtime-determined size, a stable tag-based discriminator, and a defined encoding used for serialization and cross-language exchange.

Safety requires validating the tag before accessing the payload and handling endianness and alignment correctly. Common use cases include network protocols with heterogeneous frames, binary file formats, and data interchange schemas where fields vary between records. Performance considerations involve the cost of indirection, memory management, and potential fragmentation, balanced against the flexibility gained.

It is not a standard type in mainstream languages, but concepts similar to variants, sum types, and dynamic blobs appear in several ecosystems. A minimal encoding might place a one-byte type tag, a two- to four-byte length, and a payload of variable length.

See also: variant, tagged union, dynamic type, blob, serialization.