Tsuki

Tsuki is a port of Lua 5.4 to Rust. This is porting, not binding; which mean all code are Rust and can be using without C compiler¹. The initial works was done by C2Rust. Note that this port was done without compatibility with the previous version. You can see a list of the differences here.

Important

All types in Tsuki does not implement Send and Sync and no plan to implement this at the moment.

Status

The VM to run Lua code is fully working almost exactly as vanilla Lua (see the list of differences below). Some functions on Lua standard library are still missing.

Safety

All public API of Tsuki should provide 100% safety as long as you don't use unsafe API incorrectly.

Note that currently there is no way to limit the amount of memory to be used by Lua scripts. If this unacceptable you should not use Tsuki for now until this feature is implemented.

Features

• 100% Rust code.
  • libc is required at the moment.
• Support both synchronous and asynchronous.
• Safe and low overhead API.
• Any error propagated to the caller via Rust Result instead of a long jump.
• core::any::Any as Lua userdata and can be created without the need to define its metatable.
• Metatable for a userdata is lookup with core::any::TypeId instead of a string.

Differences from Lua

Language

• Binary chunk is not supported.
• Panic when memory allocation is failed without retry (Rust behavior).
• Chunk name does not have a prefix (e.g. @).
• Second argument to __close metamethod always nil.
• __gc metamethod is not supported.
• __name metavalue must be UTF-8 string.
• __tostring metamethod must return a UTF-8 string.
• C locale is ignored (once libc has been completely removed).

Standard library

• No _VERSION, collectgarbage, dofile, loadfile, xpcall, string.dump and debug library.
• Second argument of assert accept only a UTF-8 string.
• Arguments of error:
  • First argument accept only a UTF-8 string.
  • Second argument is not supported and it is always assume 1.
• Arguments of load:
  • First argument accept only a string.
  • Second argument accept only a UTF-8 string and will be empty when absent.
  • Third argument must be nil or "t".
• warn is enabled by default without message prefixes and does not support control message.
• string.format requires UTF-8 string for both format string and format value.
• Native module is not supported.
• Environment variable LUA_PATH and LUA_PATH_5_4 is ignored.
• LUA_NOENV in registry is ignored.

Non-goals

• Become a superset of Lua (e.g. Luau).
• C API compatibility.
• Stand-alone mode.
• 16-bit systems.

Roadmap

• Remove libc.
• JIT using Cranelift.

License

Same as Lua, which is MIT.

Footnotes

1. On Windows, a proxy to sprintf written in C++ is required at the moment. This proxy will be removed when we replace sprintf calls with Rust equivalent. ↩