Add library support to Luacontrollers

This allows mods to provide their own libraries that can be accessed from within a Luacontroller, for example to make working with advanced digilines peripherals somewhat easier.
Libraries can be added to the mesecon.luacontroller_libraries table, and then the code running in the Luacontroller can use require() to request one. require() will return nil if the library is not present.

mesecons/util.lua

@@ -193,6 +193,25 @@ function mesecon.tablecopy(obj) -- deep copy
 	return obj
 end
 
+-- Performs a deep copy of a table, changing the environment of any functions.
+-- Adapted from the builtin table.copy() function.
+function mesecon.tablecopy_change_env(t, env, seen)
+	local n = {}
+	seen = seen or {}
+	seen[t] = n
+	for k, v in pairs(t) do
+		if type(v) == "function" then
+			local newfunc = v
+			setfenv(newfunc, env)
+			n[(type(k) == "table" and (seen[k] or mesecon.tablecopy_change_env(k, env, seen))) or k] = newfunc
+		else
+		n[(type(k) == "table" and (seen[k] or mesecon.tablecopy_change_env(k, env, seen))) or k] =
+			(type(v) == "table" and (seen[v] or mesecon.tablecopy_change_env(v, env, seen))) or v
+		end
+	end
+	return n
+end
+
 -- Returns whether two values are equal.
 -- In tables, keys are compared for identity but values are compared recursively.
 -- There is no protection from infinite recursion.

mesecons_luacontroller/init.lua

@@ -459,6 +459,16 @@ local function get_digiline_send(pos, itbl, send_warning)
 	end
 end
 
+mesecon.luacontroller_libraries = {}
+
+local function get_require(env)
+	return function(name)
+		if mesecon.luacontroller_libraries[name] then
+			return mesecon.tablecopy_change_env(mesecon.luacontroller_libraries[name],env)
+		end
+	end
+end
+
 local safe_globals = {
 	-- Don't add pcall/xpcall unless willing to deal with the consequences (unless very careful, incredibly likely to allow killing server indirectly)
 	"assert", "error", "ipairs", "next", "pairs", "select",
@@ -546,6 +556,8 @@ local function create_environment(pos, mem, event, itbl, send_warning)
 	for _, name in pairs(safe_globals) do
 		env[name] = _G[name]
 	end
+	
+	env.require = get_require(env)
 
 	return env
 end