Variable Optimization by the Flash Compiler 2004-03-02 - By Jesse Warden
Back
Well, it started as a designer's tool. Now, the Flash Ecosystem upon us, I
think AS2 will compile to true classes in 8; my 2 cents.
-- --Original Message-- --
From: Justin Palmer [mailto:justin@(protected)]
Sent: Monday, March 01, 2004 05:45 PM
To: flashnewbie@(protected)
Subject: RE: [Flashnewbie] Variable Optimization by the Flash Compiler
Hi,
Good explanation. It leads me to think back to my Java experience, and yes
Java does not allow such things like:
<quote>
idx = 11;
function setValue(someVar){
someVar = 11;
}
setValue("myReallyReallyReallyLongVariableName" + idx);
</quote>
So I guess that is where the compiler does not need to worry about this. So
what you are saying is MM would rather have more flexibility in programming
style than they care about performance. After all Flash is/used to be a
designers tool and not a programming platform. Hmmmmmmmm.....I think they
have some decisions to make if they really want to push for leading the web
in RIA applications. Anyways thanks for the answers.
Regards,
Justin Palmer
-- --Original Message-- --
From: Darron J. Schall [mailto:darron@(protected)]
Sent: Monday, March 01, 2004 2:30 PM
To: flashnewbie@(protected)
Subject: Re: [Flashnewbie] Variable Optimization by the Flash Compiler
> I have heard many times to watch your variables lengths in your movies
> to help execute code faster and to make smaller movies. Is this true?
> If so, why?
Without knowing the complete inner workings of the Flash Player, this answer
is not guaranteed to be correct. However, this is my best educated guess
being as I have knowledge of compilers, assemblers, and emulators (virtual
machines).
The simple answer is that it takes longer to parse longer pieces of text.
When the variable's value is looked up, the name of the variable is
translated to a location in memory behind the scenes. The longer the
variable name, the longer it takes to figure out its location in the lookup
table.
The reason Flash doesn't do this automatically is pretty simple too.
Consider the following:
myReallyReallyReallyLongVariableName1 = 1;
myReallyReallyReallyLongVariableName2 = "981247"; // etc
Now, wouldn't it be cool if that was compiled down to m1 and m2,
respectively? Yup.. except..
What if there's code that dynamically does variable name lookup?
idx = 1;
this["myReallyReallyReallyLongVariableName" + idx] = 11;
Or better yet:
idx = 11;
function setValue(someVar){
someVar = 11;
}
setValue("myReallyReallyReallyLongVariableName" + idx);
The Flash compiler has no way of knowing that the string inside the brackets
is actually part of the variable name. Thus, if the variable was renamed at
compile-time, the above two lines of code would break since
this["myReallyReallyReallyLongVariableName" + idx] would be undefined.
This has been a problem with obfuscators that do renaming.. Because of
Flash's dynamic nature, it's very hard to implement. I want to say it's
impossible.. but, well, some day I hope it happens, and when it does I don't
want to eat my words.
There's also another problem that deals with MovieClip instance names. You
wouldn't want the renamed variable to be the same as a MovieClip instance..
and you'd have to udpate the .swf file to update all of the MovieClip names
if they're used as variable names. In as2, it's common to do...
class X {
private var myMovieClipInstanceNameOnTheStage:MovieClip;
}
.. so that you can reference an MC on the Stage inside of your class file.
There's just a whole lot of bookkeeping involved, and if you do it wrong
your movie won't work right. Then, the question becomes "is it my fault
that the movie doesn't work right, or did the compiler screw it up on it's
own?"
For now, you can always do renaming by hand if you know it's safe. Make
sure to keep a backup of your original code though.. :-)
-d
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