Variable Optimization by the Flash Compiler 2004-03-01 - By Justin Palmer
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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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