I'm trying to make a mod for the game Don't Starve Together, which makes use of Lua. For this reason, I can't modify their source variables/files.
In order to try to modify the world generation, I need to access a local table that was instantiated in another file (the file is called "levels.lua"). The variable name is "levellist". Is there a way to access the variable so that I can add certain elements to the table?
Namely, I want to add {"task_set", "cave_custom"} to levellist[DST_CAVE].overrides.
If someone could help or even just tell me if this is possible or not, that would be great. Thanks!
What you are trying to do simply doesn't make sense. Local variables are accessible only from the scope it was defined in, and it's nested scopes. There is no, normal, way to change it from different scopes, let alone an entirely different script.
If you want variables that all your scripts use, use globals.
Of course you can't get to local variables (i.e. "pointers") used by another function, save for obscure debug methods that are rarely exposed to user sandbox, but you don't need to. Because you do not want to modify some local variable (i.e. make it point to another table for example), but get to some table and modify value inside it. So you just need to find any place where it is exposed to you in any way.
You should somehow edit in relevant content in your question because it is PITA to Alt-Tab back and forth to your files. According to structure from comments/chat AddLevel(LEVELTYPE.SURVIVAL, ...) inserts an entry into levellist[LEVELTYPE.SURVIVAL] table. If you check levels.lua you can also see that it returns table with sandbox_levels assigned exactly to this.
So:
local levels = require "levels"
print(levels.sandbox_levels)
-- Will print "table: SOMENUMBERS" - i.e. address of levellist[LEVELTYPE.SURVIVAL]
You now can iterate it with for idx = 1, #levels.sandbox_levels or ipairs and find entry belonging to "DST_CAVE". I can't tell how field with ID will be called or how it will be structured because data is preprocessed with function Level before inserting that you did not include in the files you posted.
As others have suggested, this may not be your best strategy.
But depending on your environment, it may be possible to abuse some more esoteric features of the runtime to let you indirectly modify values that aren't "yours". Have a look at debug.sethook and setfenv.
Related
I have been given the task of creating a DXL script. First problem is that I have never used DXL before, even though I have many years experience with DOORS itself. I have been surfing the Net to seek guidance on my particular problem. I also have a few specimen DXL scripts for reference.
My new client requires that for each View of a given Module, of which there are many Views, new "reduced" Modules are to be produced reflecting each View.
By "reduced", I mean that these new Modules are to contain nothing that isn't actually needed for that View., i.e. Columns, Attributes etc. These new Modules will only have the single View.
So, the way forward as I see it, is to take copies of the single master Module, one for each View, rename those copies to reflect a given Master Module/Required View, select that required View in the given copy Module and then delete everything that is not needed by that View, i.e. available Columns, Attributes etc.
This would be simple if I had the required DXL knowledge, which I am endeavouring to pick up as fast as I can.
If at all possible, this script has to be generic and be able to work upon any of the master Module copies to produce the associated "reduced" Module reflecting a particular View.
The client aims to use the script periodically for View archiving (I know, that's the way they want it).
Clarification
Some clarification of what I believe is required, given the following text from my original question:
If at all possible, this script has to be generic and be able to work upon any of the master Module copies to produce the associated "reduced" Module reflecting a particular View.
So, say there are ten views of the master Module, outside of the DXL script, I would copy the master Module ten times, renaming each copy to reflect each of the ten views. Unless you know different, each of those ten copies will reflect the same “Absolute Number”s as are in the master Module, so no problem there?
So, starting with the first of the copied Modules, each named to reflect the View it will eventually represent, its View would be set from the ten Views available to it, that which matches its title.
The single generic DXL script would then be run against that first copy Module, the aim being to delete everything not actually needed for that view, i.e. Attributes, Columns etc. Would some kind of purging command be required in the script for any aforementioned deleted items?
The single generic DXL script would then delete ALL views from that copy Module. The log that is produced when running the script also needs capturing, but I’m not sure whether this should be done from within the script, if possible or as a separate manual task outside of the script.
The aforementioned (indented) process would then be repeated, using the same generic script, against the remaining nine copied Modules. The intension is to leave us with ten copy Modules, each one reflecting one of the ten possible Views, with each one containing only the Attributes, Columns etc. required for that View.
Creating a mirror of a module with this approach is not so easy IMO. Think e.g. about "Absolute Number". If the original module contains the numbers 15 (level 1), 2000 (level 2), 1 (level 1), you will have to create 2000 objects, purge 1997 of them and move them to the correct place.
There is a "duplicate" tool at https://www.ibm.com/developerworks/community/forums/html/topic?id=43862118-113d-4eac-b3f1-21d3b73959d1 which tries to do this, but as stated there, this script is said not to work correctly in all situations.
So, I would rather use the approach "string clipCopy (Item i); string clipPaste(Folder folderRef)". Should be faster and less error prone. But: all Out-Links will also be copied with this method, you will probably have to delete these after the copy or else the link target module(s) will have lots of In-Links.
The problem is still not so easy to solve, as every view might have DXL columns that rely on some or other attribute, and it might contain DXL attributes which again might rely on sth else. I doubt that there is a way to analyze DXL code "on the fly" and find out which columns may be deleted.
Perhaps a totally different approach would be feasible: open each view and create an export to Excel, this way you will get rid of any dynamic dependencies. Then re-import the excel sheet to a new DOORS module. You will still have the "Absolute Number" problem, but perhaps you can make a deal that you will have a pseudo attribute "Original Absolute Number" and disregard the "new" "Absolute Number"'
Quite a big task for a DXL beginner....
Update: On second thought, perhaps you might want to combine these approaches
agree with your employer that you will use an alternative attribute for Absolute Number
use a loop like Russel suggested, when creating objects remember that objects might have to be created "below" or "after" its predecessor or sibling
for DXL attributes do not copy the DXL code but the actual current value of the object
for DXL columns create pseudo attributes _ and create a new view that uses these pseudo attributes instead of the original value
Copying the entire module, then deleting everything not in that view, seems worse than just copying the things you need from each particular view.
I would take the following as the outline of your program:
for view in main module do {
for column in view do {
Find attribute for each column and store (possibly in a skip list?)
Store name of column
}
create new module
create needed types / attributes in new module
create new view in new module
for object in main module {
create object in new module
for attribute in main module {
check if attribute is in new module {
copy info from old object to new
}
}
}
}
Each of these for X in y loops should be in the DXL reference manual in some for or another.
If you need more help, let me know!
I'm trying to use phpBB3 (forum app) along with ZF2. For that, I have to include a file from the phpBB3. In theory this is as simple as:
include('/path/to/phpbb3/common.php');
$user->session_begin(); //$user is defined in common.php file
In common.php a lot of globals are defined, and after that are required some files which are using those globals.
In ZF2 simply including the common.php would not work, because the scope of the globals will not span over the required files, so I tried a little trick:
//in Application/Forum/Service
public function callForumAPI(){
$zf_dir = getcwd();
chdir('/var/www/html/phpBB3');
include('common.php');
$user->session_begin();
chdir($zf_dir);
}
Neither in this case the scope of the global variables didn't span over the required files, so all the globals where NULL in those files.
How could I solve this issue?
I consider 2 main problems:
1. Loading resources
I dont know if you changed the code of phpBB3, since if you dont, your problem is other.
Phpbb3, as many systems, doesnt let you access directly to any file, you have to go through index.php. As you can see in common.php
if (!defined('IN_PHPBB'))
{
exit;
}
IN_PHPBB is defined in index.php, so you can simply use
Also, common.php and other files, makes use of $phpbb_root_path, that is defined in index.php.
So, at least, when you are going to include common.php you need
$zf_dir = getcwd();
chdir('/var/www/html/phpBB3');
define('IN_PHPBB', true);
$phpbb_root_path = (defined('PHPBB_ROOT_PATH')) ? PHPBB_ROOT_PATH : './';
include('common.php');
...
chdir($zf_dir);
probably there are some other things you have to take care about.
2. Variable scopes
Also, consider than in PHP, like in almost every language, a variable declared inside a function, is considered local, and will be undefined outside that function. So for sure, if you do that inside callForumAPI(), you wont have any variable outside, and moreover, depending on where you are doing that includes...it could be actually inside a function, no matter you can notice it or not, since ZF2 is a framenwork with a complex, non-obvius architecture.
So, what i recomend, as soon as you load the file, is to use the ZF2 service manager to store all the variables and object than you would use in your application. This is a good measure even if you didnt need it,since this way you can have everything integrated as much as possible, it is important to minimize and localize access to phpbb3, since it is not meant to be a library, maintenance could be tricky, so if everyhing is in the same file, and then you create your own internal api through the service manager, it will more encapsulated and nicer. I assume you already know how to do this, if you dont, just let me know.
try this, and tell me if its enough or we need more research
I've heard mumblings around the internets about being able to hot-swap code in Lua similar to how it's done in Java, Erlang, Lisp, etc. However, 30 minutes of googling for it has turned up nothing. Has anyone read anything substantial about this? Anyone have any experience doing it? Does it work in LuaJIT or only in the reference VM?
I'm more interested in the technique as a shortcut in development/debugging than an upgrade path in a live environment.
Lua, and most scripting languages for that matter, do not support the most generalized form of "hot swapping" as you define it. That is, you cannot guaranteeably change a file on disk and have any changes in it propagate itself into an executing program.
However, Lua, and most scripting languages for that matter, are perfectly capable of controlled forms of hot swapping. Global functions are global functions. Modules simply load global functions (if you use them that way). So if a module loads global functions, you can reload the module again if it is changed, and those global function references will change to the newly loaded functions.
However, Lua, and most scripting languages for that matter, makes no guarantees about this. All that's happening is the changing of global state data. If someone copied an old function into a local variable, they can still access it. If your module uses local state data, the new version of the module cannot access the old module's state. If a module creates some kind of object that has member functions, unless those members are fetched from globals, these objects will always refer to the old functions, not the new ones. And so forth.
Also, Lua is not thread safe; you can't just interrupt a lua_State at some point and try to load a module again. So you would have to set up some specific point in time for it to check stuff out and reload changed files.
So you can do it, but it isn't "supported" in the sense that it can just happen. You have to work for it, and you have to be careful about how you write things and what you put in local vs. global functions.
As Nicol said, the language itself doesn't do it for you.
If you want to implement something like this yourself though, it's not that hard, the only thing "preventing" you is any "leftover" references (which will still point to the old code) and the fact require caches its return value in package.loaded.
The way I'd do it is by dividing your code into 3 modules:
the reloading logic at entry point (main.lua)
any data you want to preserve across reloads (data.lua)
the actual code to reload (payload.lua), making sure you don't keep any references to that (which is sometimes not possible when you e.g. have to give callbacks to some library; see below).
-- main.lua:
local PL = require("payload")
local D = require("data")
function reload(module)
package.loaded[module]=nil -- this makes `require` forget about its cache
return require(module)
end
PL.setX(5)
PL.setY(10)
PL.printX()
PL.printY()
-- .... somehow detect you want to reload:
print "reloading"
PL = reload("payload") -- make sure you don't keep references to PL elsewhere, e.g. as a function upvalue!
PL.printX()
PL.printY()
-- data.lua:
return {} -- this is a pretty dumb module, it's literally just a table stored in `package.loaded.data` to make sure everyone gets the same instance when requiring it.
-- payload.lua:
local D = require("data")
local y = 0
return {
setX = function(nx) D.x = nx end, -- using the data module is preserved
setY = function(ny) y = ny end, -- using a local is reset upon reload
printX = function() print("x:",D.x) end,
printY = function() print("y:", y) end
}
output:
x: 5
y: 10
reloading
x: 5
y: 0
you could flesh out that logic a bit better by having a "registry module" that keeps track of all the requiring/reloading for you and abstracts away any access into modules (thus allowing you to replace the references), and, using the __index metatable on that registry you could make it pretty much transparent without having to call ugly getters all over the place. this also means you can supply "one liner" callbacks that then actually just tail-call through the registry, if any 3rd party library needs that.
I am creating a web project and want it to be optimized. Instead of accessing lookup values in the database (to minimize access), I think it should be stored somewhere in symfony. What is the best way to this? In YML with PHP Array?
You can put values that don't change often in lib/app.yml
You can access those values by using sfConfig::get('value').
app.yml is cool because you can store enviroment specific values in it.
Another option I use for values that should never change and that are not environment-specific is to define constants in a relevant model or helper class.
The advantages are:
1) if you name those constants well using them helps make the code more self-documenting
2) if you use an IDE with autocompletion features it will look up and verify their names as you're coding.
3) they are the fastest possible method of lookup.
I'm lead dev for Bitfighter, and we're using Lua as a scripting language to allow players to program their own custom robot ships.
In Lua, you need not declare variables, and all variables default to global scope, unless declared otherwise. This leads to some problems. Take the following snippet, for example:
loc = bot:getLoc()
items = bot:findItems(ShipType) -- Find a Ship
minDist = 999999
found = false
for indx, item in ipairs(items) do
local d = loc:distSquared(item:getLoc())
if(d < minDist) then
closestItem = item
minDist = d
end
end
if(closestItem != nil) then
firingAngle = getFiringSolution(closestItem)
end
In this snippet, if findItems() returns no candidates, then closestItem will still refer to whatever ship it found the last time around, and in the intervening time, that ship could have been killed. If the ship is killed, it no longer exists, and getFiringSolution() will fail.
Did you spot the problem? Well, neither will my users. It's subtle, but with dramatic effect.
One solution would be to require that all variables be declared, and for all variables to default to local scope. While that change would not make it impossible for programmers to refer to objects that no longer exist, it would make it more difficult to do so inadvertently.
Is there any way to tell Lua to default all vars to local scope, and/or to require that they be declared? I know some other languages (e.g. Perl) have this option available.
Thanks!
Lots of good answers here, thanks!
I've decided to go with a slightly modified version of the Lua 'strict' module. This seems to get me where I want to go, and I'll hack it a little to improve the messages and make them more appropriate for my particular context.
There is no option to set this behavior, but there is a module 'strict' provided with the standard installation, which does exactly that (by modifying the meta-tables).
Usage:
require 'strict'
For more in-depth info and other solutions: http://lua-users.org/wiki/DetectingUndefinedVariables, but I recommend 'strict'.
Sorta.
In Lua, globals notionally live in the globals table _G (the reality is a bit more complex, but from the Lua side there's no way to tell AFAIK). As with all other Lua tables, it's possible to attach a __newindex metatable to _G that controls how variables are added to it. Let this __newindex handler do whatever you want to do when someone creates a global: throw an error, permit it but print a warning, etc.
To meddle with _G, it's simplest and cleanest to use setfenv. See the documentation.
"Local by default is wrong". Please see
http://lua-users.org/wiki/LocalByDefault
http://lua-users.org/wiki/LuaScopingDiscussion
You need to use some kind of global environment protection. There are some static tools to do that (not too mature), but the most common solution is to use runtime protection, based on __index and __newindex in _G's metatable.
Shameles plug: this page may also be useful:
http://code.google.com/p/lua-alchemy/wiki/LuaGlobalEnvironmentProtection
Note that while it discusses Lua embedded into swf, the described technique (see sources) do work for generic Lua. We use something along these lines in our production code at work.
Actually, the extra global variable with the stale reference to the ship will be sufficient to keep the GC from discarding the object. So it could be detected at run time by noticing that the ship is now "dead" and refusing to do anything with it. It still isn't the right ship, but at least you don't crash.
One thing you can do is to keep user scripts in a sandbox, probably a sandbox per script. With the right manipulation of either the sandbox's environment table or its metatable, you can arrange to discard all or most global variables from the sandbox before (or just after) calling the user's code.
Cleaning up the sandbox after calls would have the advantage of discarding extra references to things that shouldn't hang around. This could be done by keeping a whitelist of fields that are allowed to remain in the environment, and deleting all the rest.
For example, the following implements a sandboxed call to a user-supplied function with an environment containing only white-listed names behind a fresh scratch table supplied for each call.
-- table of globals that will available to user scripts
local user_G = {
print=_G.print,
math=_G.math,
-- ...
}
-- metatable for user sandbox
local env_mt = { __index=user_G }
-- call the function in a sandbox with an environment in which new global
-- variables can be created and modified but they will be discarded when the
-- user code completes.
function doUserCode(user_code, ...)
local env = setmetatable({}, env_mt) -- create a fresh user environment with RO globals
setfenv(user_code, env) -- hang it on the user code
local results = {pcall(user_code, ...)}
setfenv(user_code,{})
return unpack(results)
end
This could be extended to make the global table read-only by pushing it back behind one more metatable access if you wanted.
Note that a complete sandbox solution would also consider what to do about user code that accidentally (or maliciously) executes an infinite (or merely very long) loop or other operation. General solutions for this are an occasional topic of discussion on the Lua list, but good solutions are difficult.