cityjson-lib-ffi-core

cityjson-lib-ffi-core is the shared low-level C ABI for the release-facing bindings in this repository.

It intentionally stays small and explicit:

• opaque model handles with owned transfer helpers
• stable status and error categories
• parse, serialize, summary, and workflow entry points
• opaque model-selection handles for CityObject and geometry extraction workflows
• generated C headers under include/cityjson_lib/cityjson_lib.h

The C++ and Python bindings build on this crate. The wasm adapter uses the same substrate internally, but it is not part of the public release surface yet.

Selection and merge ABI

The C core exposes the same selection carrier used by the Rust operations API as an opaque cj_model_selection_t*. Callers create selections from a model, combine or expand them as needed, then pass them back to cj_model_extract_selection(...) to materialize a new cj_model_t*.

cj_string_view_t ids[] = {
    {.data = (const uint8_t *)"building-part-1", .len = 15},
};

cj_model_selection_t *selection = NULL;
cj_status_t status = cj_model_select_cityobjects_by_id(
    model,
    ids,
    1,
    &selection);

cj_model_selection_t *with_relatives = NULL;
status = cj_model_selection_include_relatives(selection, model, &with_relatives);

cj_model_t *extracted = NULL;
status = cj_model_extract_selection(model, with_relatives, &extracted);

cj_model_free(extracted);
cj_model_selection_free(with_relatives);
cj_model_selection_free(selection);

Geometry-level selection uses cj_geometry_selection_spec_t, pairing a CityObject id with the geometry index inside that CityObject. Selection handles can be combined with cj_model_selection_union(...) and cj_model_selection_intersection(...); cj_model_selection_is_empty(...) reports whether a selection has no retained CityObjects or geometries.

Multiple complete models can be merged through cj_model_merge_models(...). The array must contain at least one non-null cj_model_t*; the returned model is owned by the caller and must be released with cj_model_free(...).

This crate is dual-licensed under MIT or Apache-2.0. See the package metadata and the license files in this repository.