/tg/ Station 13 - Modules - Types

Auxlua


Datums

DM datums are treated as Lua userdata, and can be stored in fields. Regular datums are referenced weakly, so if a datum has been deleted, the corresponding userdata will evaluate to nil when used in comparisons or functions.

Keep in mind that BYOND can't see that a datum is referenced in a Lua field, and will garbage collect it if it is not referenced anywhere in DM.

datum:get_var(var)

Equivalent to DM's datum.var

datum:set_var(var, value)

Equivalent to DM's datum.var = value

datum:call_proc(procName, ...)

Equivalent to DM's datum.procName(...)


Lists

In order to allow lists to be modified in-place across the DM-to-Lua language barrier, lists are treated as userdata. Whenever running code that expects a DM value, auxlua will attempt to convert tables into lists.

List references are subject to the same limitations as datum userdata, but you are less likely to encounter these limitations.

list.len

Equivalent to DM's list.len

list:get(index)

Equivalent to DM's list[index]

list:set(index, value)

Equivalent to DM's list[index] = value

list:add(value)

Equivalent to DM's list.Add(value)

list:to_table()

Converts a DM list into a lua table.

list:of_type(type_path)

Will extract only values of type type_path.


The dm table

The dm table consists of the basic hooks into the DM language.

dm.state_id

The address of the Lua state in memory. This is a copy of the internal value used by auxlua to locate the Lua state in a global hash map.

dm.global_proc(proc, ...)

Calls the global proc /proc/[proc] with ... as its arguments.

dm.world

A reference to DM's world, in the form of datum userdata. This reference will never evaluate to nil, since world always exists.

Due to limitations inherent in the wrapper functions used on tgstation, world:set_var and world:call_proc will raise an error.

dm.global_vars

A reference to DM's global, in the form of datum userdata. Subject to the same limitations as dm.world

dm.usr

A weak reference to DM's usr. As a rule of thumb, this is a reference to the mob of the client who triggered the chain of procs leading to the execution of Lua code. The following is a list of what usr is for the most common ways of executing Lua code:

  • For resumes and awakens, which are generally executed by the MC, usr is (most likely) null.
  • SS13.wait queues a resume, which gets executed by the MC. Therefore, usr is null after SS13.wait finishes.
  • For chunk loads, usr is generally the current mob of the admin that loaded that chunk.
  • For function calls done from the Lua editor, usr is the current mob of the admin calling the function.
  • SS13.register_signal creates a /datum/callback that gets executed by the SEND_SIGNAL macro for the corresponding signal. As such, usr is the mob that triggered the chain of procs leading to the invocation of SEND_SIGNAL.

Task management

The Lua Scripting subsystem manages the execution of tasks for each Lua state. A single fire of the subsystem behaves as follows:

  • All tasks that slept since the last fire are resumed in the order they slept.
  • For each queued resume, the corresponding task is resumed.

sleep()

Yields the current thread, scheduling it to be resumed during the next fire of SSlua. Use this function to prevent your Lua code from exceeding its allowed execution duration. Under the hood, sleep performs the following:

  • Sets the global flag __sleep_flag
  • Calls coroutine.yield()
  • Clears the sleep flag when determining whether the task slept or yielded
  • Ignores the return values of coroutine.yield() once resumed

The SS13 package

The SS13 package contains various helper functions that use code specific to tgstation.

SS13.state

A reference to the state datum (/datum/lua_state) handling this Lua state.

SS13.global_proc

A wrapper for the magic string used to tell WrapAdminProcCall to call a global proc. For instance, /datum/callback must be instantiated with SS13.global_proc as its first argument to specify that it will be invoking a global proc. The following example declares a callback which will execute the global proc to_chat:

local callback = SS13.new("/datum/callback", SS13.global_proc, "to_chat", dm.world, "Hello World")

SS13.istype(thing, type)

Equivalent to the DM statement istype(thing, text2path(type)).

SS13.new(type, ...)

Instantiates a datum of type type with ... as the arguments passed to /proc/_new The following example spawns a singularity at the caller's current turf:

SS13.new("/obj/singularity", dm.global_proc("_get_step", dm.usr, 0))

SS13.await(thing_to_call, proc_to_call, ...)

Calls proc_to_call on thing_to_call, with ... as its arguments, and sleeps until that proc returns. Returns two return values - the first is the return value of the proc, and the second is the message of any runtime exception thrown by the called proc. The following example calls and awaits the return of poll_ghost_candidates:

local ghosts, runtime = SS13.await(SS13.global_proc, "poll_ghost_candidates", "Would you like to be considered for something?")

SS13.wait(time, timer)

Waits for a number of seconds specified with the time argument. You can optionally specify a timer subsystem using the timer argument.

Internally, this function creates a timer that will resume the current task after time seconds, then yields the current task by calling coroutine.yield with no arguments and ignores the return values. If the task is prematurely resumed, the timer will be safely deleted.

SS13.register_signal(datum, signal, func, make_easy_clear_function)

Registers the Lua function func as a handler for signal on datum.

Like with signal handlers written in DM, Lua signal handlers should not sleep (either by calling sleep or coroutine.yield).

If make_easy_clear_function is truthy, a member function taking no arguments will be created in the SS13 table to easily unregister the signal handler.

This function returns the /datum/callback created to call func from DM.

The following example defines a function which will register a signal that makes target make a honking sound any time it moves:

function honk(target)
	SS13.register_signal(target, "movable_moved", function(source)
		dm.global_proc("playsound", target, "sound/items/bikehorn.ogg", 100, true)
	end)
end

SS13.unregister_signal(datum, signal, callback)

Unregister a signal previously registered using SS13.register_signal. callback should be a datum/callback previously returned by SS13.register_signal. If callback is not specified, ALL signal handlers registered on datum for signal will be unregistered.

SS13.set_timeout(time, func)

Creates a timer which will execute func after time seconds. func should not expect to be passed any arguments, as it will not be passed any. Unlike SS13.wait, SS13.set_timeout does not yield or sleep the current task, making it suitable for use in signal handlers for SS13.register_signal

The following example will output a message to chat after 5 seconds:

SS13.set_timeout(5, function()
	dm.global_proc("to_chat", dm.world, "Hello World!")
end)

Internal globals

Auxlua defines several globals for internal use. These are read-only.

__sleep_flag

This flag is used to designate that a yielding task should be put in the sleep queue instead of the yield table. Once auxlua determines that a task should sleep, __sleep_flag is cleared.

__set_sleep_flag(value)

A function that sets __sleep_flag to value. Calling this directly is not recommended, as doing so muddies the distinction between sleeps and yields.

__sleep_queue

A sequence of threads, each corresponding to a task that has slept. When calling /proc/__lua_awaken, auxlua will dequeue the first thread from the sequence and resume it. Threads in this queue can be resumed from Lua code, but doing so is heavily advised against.

__yield_table

A table of threads, each corresponding to a coroutine that has yielded. When calling /proc/__lua_resume, auxlua will look for a thread at the index specified in the index argument, and resume it with the arguments specified in the arguments argument. Threads in this table can be resumed from Lua code, but doing so is heavily advised against.

__task_info

A table of key-value-pairs, where the keys are threads, and the values are tables consisting of the following fields:

  • name: A string containing the name of the task
  • status: A string, either "sleep" or "yield"
  • index: The task's index in __sleep_queue or __yield_table

The threads constituting this table's keys can be resumed from Lua code, but doing so is heavily advised against.