[Lua] Unit ID string to integer

[strange_loop]

I'm new around here and I just recently started getting into W3 scripting now that Lua is a thing! I came up with a function that might be useful. If it's not, please just archive this thread and carry on

Functions like

native CreateUnit takes player id, integer unitid, real x, real y, real face returns unit

expect an integer unit id. In JASS, you can pass a 4-character string (such as "hfoo" for a footman) as an integer and Jass converts the string into its corresponding bytes. Lua does not do this automatically and it's more tricky. Here's a short little utility function that does this conversion.

function getUnitId (idString)
    local b1, b2, b3, b4 = string.byte(idString, 1, 4)
    return (b1 << 24) | (b2 << 16) | (b3 << 8) | b4
end

Then you can use it like this

local unit = CreateUnit(GetLocalPlayer(), getUnitId("hfoo"), 0, 0, 0)

Is there an easier solution that I'm not aware of? If not, I hope this serves useful!

 

[Pyrogasm]

There is a default Lua function that does this: FourCC("i000")

 

[Bribe]

There is a default Lua function that does this: FourCC("i000")

Came here to say this.

 

[strange_loop]

Good to know. I'm looking at the Lua reference and don't see that function. Nor do I see it in common.j. Where is it from?

 

[Dr Super Good]

There is also a way to do this by using string.unpack to unpack a 4 character type ID as an integer.

 

[yxq1122]

This is an issue that also confuses me. If any one could present a tutorial that clarifies the differences between Jass/vJass and Lua, it would be great.

 

[Prometheus3375]

Just read Lua manual on Lua site. 'word' and "word" are strings, quotes can be either single or double.

 

[~El]

This is an issue that also confuses me. If any one could present a tutorial that clarifies the differences between Jass/vJass and Lua, it would be great.

It doesn't really make sense to approach Lua in terms of its differences from Jass, because there's just so many. It's a different language with a different history and semantics. There's a lot of things that are done one way in Jass that are done differently in Lua. If you want to program in it, you should really just learn it like any other new language that isn't JASS, and not make any assumptions about its semantics. The PIL book is a good starting point.

 

[Bribe]

Syntax-wise, conversion from JASS to Lua is mostly find and replace:

Endfunction/loop/if become end
Loop becomes while (true) do
!= becomes ~=
Takes becomes (
Returns becomes )
Null becomes nil
Delete all types (integer, boolean, agent)

Exitwhen works differently (just uses 'break') and you may want to utilize some more simple iterations provided by Lua. For that you need to look over the Lua loop tutorials.

Arrays are declared differently - instead of "array name" it is "name = {}".

Arrays are not pre-initialized so sometimes you have to manually initialize indices.

Arrays are virtually infinite and work similarly to Hashtables (so no need for the Table vJass library).

Functions are just variables and can be assigned and passed dynamically. Calling code is very lightweight.

Plenty of others!

 

[~El]

Syntax-wise, conversion from JASS to Lua is mostly find and replace:

Endfunction/loop/if become end
Loop becomes while (true) do
!= becomes ~=
Takes becomes (
Returns becomes )
Null becomes nil
Delete all types (integer, boolean, agent)

Exitwhen works differently (just uses 'break') and you may want to utilize some more simple iterations provided by Lua. For that you need to look over the Lua loop tutorials.

Arrays are declared differently - instead of "array name" it is "name = {}".

Arrays are not pre-initialized so sometimes you have to manually initialize indices.

Arrays are virtually infinite and work similarly to Hashtables (so no need for the Table vJass library).

Functions are just variables and can be assigned and passed dynamically. Calling code is very lightweight.

Plenty of others!

There's also:

- Arrays are 1-indexed, unlike most other languages
- You don't need to null local variables
- Equality comparisons between handle types are currently somewhat broken and don't work. If you have two "unit" variables that come from different "sources", they may not compare equal. This is a major difference to jass, where equality comparisons work correctly.
- Strings are not limited to 2040-whatever character, and can be basically treated as binary buffers

This is why I don't recommend blindly rewriting existing JASS code in Lua. It will probably work, but unless you pay attention to all the small details and differences, you're going to run into some trouble. If you don't already know Lua and just think its a different version of JASS, you're going to run into a lot of trouble.

 

[Dr Super Good]

- Arrays are 1-indexed, unlike most other languages

Only when operating in list mode. Lua itself will still accept index 0 as valid, although with a performance impact (hash table rather than array).

 

[~El]

Only when operating in list mode. Lua itself will still accept index 0 as valid, although with a performance impact (hash table rather than array).

Unfortunately, a lot of things assume 1-based indexing in lua. The length operator (#) only counts elements from 1. table.insert will insert into an empty table at position 1. Table literals enumerate elements starting from 1. ipairs will only iterate starting from 1 as well. And like you mentioned, there's a performance impact associated with using 0 as an index.

 

[Pyrogasm]

Equality comparisons between handle types are currently somewhat broken and don't work. If you have two "unit" variables that come from different "sources", they may not compare equal. This is a major difference to jass, where equality comparisons work correctly.

So instead just compare handle ids?

 

[~El]

So instead just compare handle ids?

Yes, that's the solution for now. It's just important to note since this is a major difference to JASS. Blizzard is aware of this issue and they'll hopefully fix it in the future, however.

 

[Prometheus3375]

Another difference between JASS and Lua - boolexp are cached in JASS, but not in Lua. I.e. every time you call Condition() or Filter() for the same callback, boolexpr will be created only once in JASS, in Lua a new boolexpr will be created every time.

 

[Dr Super Good]

Another difference between JASS and Lua - boolexp are cached in JASS, but not in Lua. I.e. every time you call Condition() or Filter() for the same callback, boolexpr will be created only once in JASS, in Lua a new boolexpr will be created every time.

And is this a leak hazard?

 

[Tasyen]

one does not write "call" as one does not write "set".
Combines 2 strings with 2 "." example: "Hello" .. " World"
comments are -- it also supports multiline comments --[[ to --]]
one does not need a globals block (for variables) or Init_trig function, one can just write that lines defining variables, CreatingTriggers, starting timers... anywhere outside of functions.

This code can be placed anywhere outside of functions in Lua mode and it will create an any unit attacked trigger. That trigger prints attack Units. Prints after game started "TestTimer" and sets Reds Gold to 5000 before map Init TriggersActions were executed.

MyTrigger = CreateTrigger()
TriggerRegisterAnyUnitEventBJ(MyTrigger, EVENT_PLAYER_UNIT_ATTACKED)
TriggerAddAction(MyTrigger, function() print(GetUnitName(GetAttacker()), "attacks", GetUnitName(GetTriggerUnit())) end)
function Test()
    print("TestTimer")
end
TimerStart(CreateTimer(),0.0, false, Test)

function TestGold()
    SetPlayerState(Player(0), PLAYER_STATE_RESOURCE_GOLD, 5000)
end
TestGold()

Edit: MyTrigger is seen as garbage and is cleaned when the garbage collector runs.

 

[Prometheus3375]

And is this a leak hazard?

Yes.
Here (JASS) filter will be created once.

call GroupEnumUnitsInRange(g, x, y, r, Filter(function SomeFunc))

Here (Lua) filter will be created every time you execute this string.

GroupEnumUnitsInRange(g, x, y, r, Filter(SomeFunc))

You can check this easily just comparing handle ids every time.

 

[Tasyen]

Does running the garbage collector afterwards changes the result? I also thought that annonym functions in ForGroup/TimerStart would leak cause the handleIds were rising, but after forcing the garbage collector to run the ids were reused after 3 further executions of the same function. This function forced collectgarbage() as last action. collectgarbage was only added for the test.

 

[Prometheus3375]

Does running the garbage collector afterwards changes the result?

Perhaps, I did not make that test, it was made by one of XGM users.

after forcing the garbage collector to run the ids were reused after 3 further executions of the same function.

You are correct.
Create test map where N times per second you create and instantly delete timer outputting its handle id. In JASS they will be close to each other, in Lua handle id will increase. But if you add collectgarbage() at the end in Lua code then it will behave as JASS code.

Therefore, there is a big question when garbage collector runs automatically in WC3 Lua. Calling collectgarbage() manually in heavy maps can lead to freezes and may cause desyncs. Everything depends on how Blizzard have implemented Lua in WC3.

 

[Bribe]

I suppose this can be rectified by manually overwriting the Filter() native to cache the original boolexpr. Condition() probably works the same way, but is typically only utilized once in GUI triggerconditions.

 

[~El]

I believe if you're running in Lua mode, you can just pass a function directly, without having to wrap it into a Filter or a Condition.

 

[Bribe]

I believe if you're running in Lua mode, you can just pass a function directly, without having to wrap it into a Filter or a Condition.

I've not tried, but that sounds like a cool thing to test. I bet there would be a performance improvement in triggerconditions linked to code rather than boolexpr if so.

 

[Dr Super Good]

Therefore, there is a big question when garbage collector runs automatically in WC3 Lua. Calling collectgarbage() manually in heavy maps can lead to freezes and may cause desyncs. Everything depends on how Blizzard have implemented Lua in WC3.

They use the standard incremental garbage collector. Nothing magical or hidden about it.

By default it aims to complete a collection cycle around the time that the Lua virtual machine heap size has grown to double the size it was after the last collection cycle. It does the collection incrementally so as to avoid freezing the application for an extended period. The rate at which an increment traverses the heap and the rate at which full collection cycles complete can be adjusted as required. Garbage collection is client local, meaning that use of __gc metafunction is prone to OoS errors.

Be aware that the Lua garbage collector in default operating mode runs at a rate determined by the Lua heap and not the Warcraft III heap. This is important since Warcraft III objects are not factored into the Lua heap size so even if a garbage collection cycle would free them, it may take a very long time to happen since they effectively multiply the garbage memory size without influencing the collector rate. One can work around this by setting the collector to run more frequently by setting its memory multiplier target to a smaller number. For example if the Warcraft III garbage is 3 times the Lua heap garbage then setting the collector to run at 125% heap size would yield the desired doubling in memory frequency.

Explicitly calling collectgarbage() forces the completion of a full garbage collection cycle. It will complete any underway incremental cycle. One should much rather adjust the collection frequency parameters or instruct it to run an incremental work. The incremental work mode will tell you when the work done resulted in the completion of the current cycle. Incremental work mode is recommended in your case since it will avoid freezes, however be aware that due to heap size variances incremental mode shares the same OoS hazards as the standard garbage collector.

Adjusting the default garbage collector parameters is the most recommended approach as Lua is smart enough to handle its own garbage collection and heap as long as one tunes it appropriately. One should only force full garbage collection cycles if one uses __gc metafunctions which are an OoS hazard, for example my Lua location/group/force garbage collector.

 

[Prometheus3375]

without having to wrap it into a Filter or a Condition

You must wrap it, since boolexpr is expected. I also didn't test it, but some people say that wrapping is necessary or error will be thrown.

 

[WaterKnight]

@Prometheus3375 Then overwrite Filter/Condition. I had used the behavior of them before to assign unique ids to code values (functions). That's not necessary in Lua anymore, however. You can use function pointers as table keys.

 

[yxq1122]

There is also a way to do this by using string.unpack to unpack a 4 character type ID as an integer.

Can this method return a correct unit/item type ID (same as that in Jass)?

Syntax-wise, conversion from JASS to Lua is mostly find and replace:

Endfunction/loop/if become end
Loop becomes while (true) do
!= becomes ~=
Takes becomes (
Returns becomes )
Null becomes nil
Delete all types (integer, boolean, agent)

Exitwhen works differently (just uses 'break') and you may want to utilize some more simple iterations provided by Lua. For that you need to look over the Lua loop tutorials.

Arrays are declared differently - instead of "array name" it is "name = {}".

Arrays are not pre-initialized so sometimes you have to manually initialize indices.

Arrays are virtually infinite and work similarly to Hashtables (so no need for the Table vJass library).

Functions are just variables and can be assigned and passed dynamically. Calling code is very lightweight.

Plenty of others!

Thanks a lot, @Bribe. You present a prototype of a Jass2Lua converter. But how about the issue of this thread? Any other good solutions?

 

[Bribe]

Can this method return a correct unit/item type ID (same as that in Jass)?


Thanks a lot, @Bribe. You present a prototype of a Jass2Lua converter. But how about the issue of this thread? Any other good solutions?

Just use FourCC as had been earlier recommended. This thread has been resolved for a long time.