libcubescript

Overview

Libcubescript is an embeddable implementation of the CubeScript scripting language. CubeScript is the console/config language of the Cube engines/games (and derived engines/games). It's a simplistic language defined around the idea of everything being a string, with Lisp-like syntax (allowing various control structures to be defined as commands).

Benefits and use cases

CubeScript is suitable for any use that calls for a simple scripting language that is easy to embed. It's particularly strong at macro processing, so it can be used as a preprocessor, or for any string-heavy use. Since it has descended from a console language for a video game, it can still be used for that very purpose, as well as a configuration file language.

Its thread-friendliness allows for usage in any context that requires parallel processing and involvement of the scripting system in it.

As far as benefits over the original implementation go, while it is based on the original implementation, it's largely rewritten; thus, it's gained many advantages, including:

• Independent implementation (can be embedded in any project)
• No global state (multiple CubeScripts in a single program)
• Modern C++20 API
• C++ lambdas can be used as commands (including captures and type inference)
• Error handling including recovery (protected call system similar to Lua)
• Stricter parsing (strings cannot be left unfinished etc.)
• Loop control statements (break and continue)
• No manual memory mangement, values manage themselves
• Clean codebase that is easy to read and contribute to
• Support for arbitrary size integers and floats (can be set at compile time)
• Allows building into a static or shared library, supports -fvisibility=hidden
• Custom allocator support (control over how heap memory is allocated)

There are some features that are a work in progress and will come later:

• More helpful debug information (proper line infos at both parse and run time)
• A degree of thread safety (see below)
• Coroutines

The API is currently very unstable, as is the actual codebase. Therefore you should not use the project in production environments just yet, but you're also free to experiment - feedback is welcome.

The project is also open for contributions. You can use pull requests on GitHub and there is also a discussion channel #octaforge on FreeNode; this project is a part of the larger OctaForge umbrella.

Threads and coroutines

(In progress)

Libcubescript supports integration with coroutines and threads by providing a concept of threads itself. You can create a thread (child state) using the main state and it will share global data with the main state, but it also has its own call stack.

The "global" state is thread safe, allowing concurrent access from multiple threads. The "local" state can be yielded as a part of the coroutine without affecting any other threads.

This functionality is not exposed into the language itself, but it can be utilized in the outside native code.

Building and usage

There are no dependencies (other than a suitable compiler and the standard library).

Libcubescript is built using meson. After installing it, you can do something like this:

mkdir build && cd build
meson ..
ninja all

Link the libcubescript library together with your application and everything should just work. It also builds the REPL by default.

For the REPL (when not disabled with -Drepl=disabled) you have a choice of two line editing libraries - either the readline library (which is always disabled by default, so you need to enable it manually) or the linenoise library (bundled and enabled by default). There is also a fallback without any line editing, used when you disable both (but then there is no line editing or history).

The version of linenoise bundled with the project is cpp-linenoise, available at https://github.com/yhirose/cpp-linenoise. Our version is modified, so that it builds cleanly with our flags, and so that it supports the "hints" feature available in original linenoise. Other than the modifications, it is baseed on upstream git revision a927043cdd5bfe203560802e56a7e7ed43156ed3.

Licensing

See COPYING.md for licensing information.