liboscore

This is the main crate of libOSCORE when accessing libOSCORE through Rust.

It performs different tasks that are relatively tightly coupled:

• It builds the C header files for the Rust backend implementations using cbindgen.
• It configures and builds Rust "header" files from the C header files (excluding types that are already native Rust types), as a -sys crate would do.
• It compiles the C files of liboscore directly for static linking.
• It implements coap-message on top of OSCORE protected messages.

At present, it pulls in both the cryptography and the message backends written in Rust (liboscore-cryptobackend and liboscore-msgbackend). Making the cryptography backend optional would be simple and straightforward (and is just waiting for an application to need it). Using an non-Rust message backend would be possible in theory, but the author fails to imagine when that would be useful. Some extra constructors for protected messages might be needed.