GVariant

GVariant is a data type in the GLib core library designed to hold a value together with its type information. It is immutable once created and is used to simplify inter-process communication and data serialization. GVariant values are described by a type signature, a string notation that encodes primitive and container types, such as s for string, i for 32-bit integer, b for boolean, and container forms like a{sv} for a dictionary mapping strings to variants, and (si) for a two-element tuple.

Implementation revolves around a small runtime type system composed of GVariantType objects that describe the shape of a value, and GVariant values themselves that store the data. The API favors efficiency through immutability and zero-copy representations where possible, and it uses reference counting for memory management via appropriate functions.

GLib provides builders and iterators for working with complex values: GVariantBuilder constructs nested variants, and GVariantIter allows streaming access to elements in arrays and dictionaries. Functions exist to print and parse textual representations as well as to integrate with D-Bus (GDBus) and GSettings, where GVariant is the standard value container.

GVariant is a central data container in GNOME software stacks because it enables robust, typed, and portable data exchange between processes and components. Its design emphasizes type-safety, cross-process compatibility, and efficient memory handling, making it a foundational element in GLib-based applications.