rust-and-c++.md

Rust and C++

Taskwarrior has historically been a C++ project, but as of taskwarrior-3.0.0, the storage backend is now provided by a Rust library called TaskChampion.

TaskChampion

TaskChampion implements storage and access to "replicas" containing a user's tasks. It defines an abstract model for this data, and also provides a simple Rust API for manipulating replicas. It also defines a method of synchronizing replicas and provides an implementation of that method in the form of a sync server. TaskChampion provides a C interface via the taskchampion-lib crate, at src/tc/lib.

Other applications, besides Taskwarrior, can use TaskChampion to manage tasks. Taskwarrior is just one application using the TaskChampion interface.

Taskwarrior's use of TaskChampion

Taskwarrior's interface to TaskChampion has a few layers:

• A Rust library, takschampion-lib, that presents extern "C" functions for use from C++, essentially defining a C interface to TaskChampion.
• C++ wrappers for the types from taskchampion-lib, defined in src/tc, ensuring memory safety (with unique_ptr) and adding methods corresponding to the Rust API's methods. The wrapper types are in the C++ namespace, tc.