typemapping

Typemapping is the process of relating or translating data types between different type systems or data representation formats. It is used to enable interoperability between programming languages, database schemas, and data interchange formats. Typemapping can be explicit, where developers provide conversion rules or functions that define how each source type maps to a target type, or implicit, where a language or library applies automatic casting or coercion.

In programming, typemapping is common in foreign function interfaces and language bindings, where a source language must represent values defined in another language, such as mapping C integers to the host language integer types, or mapping pointers to opaque wrappers. In databases and APIs, typemapping aligns SQL or JSON types with in-memory types, handling issues like nullability, precision, and complex structures.

Key challenges include preserving precision and range, handling nulls, and mapping complex types such as arrays, maps, unions, or user-defined types. Version compatibility and platform differences can complicate mappings over time. To address these, typemapping often relies on schema-driven rules, metadata annotations, or code generation, producing boilerplate conversion code or runtime libraries that implement the mappings.

Related concepts include type conversion versus type coercion, and typemaps used in tools such as SWIG for wrapping C/C++ libraries for higher-level languages. Proper typemapping improves data integrity, performance, and interoperability in multi-language ecosystems.