Re: Re: Calculating Methods' Local Variable Sizes at Runtime

Thanks Eugene for the reply.

yes, using visitLocalVariable I am able to identify the set of parameters
passed to a method. What I can't figure out is how to get the actual values
for these parameters off the stack to calculate their real sizes. I can
figure out their names and their types from the method signature, and for
the primitive types a lookup table can give me the size of their memory
usage. What I don't know, is how to get the actual size of non-primitive
parameters. If the nonprimitive type contains an array or a list, the length
of the array or the list also size becomes a critical factor in figuring out
the amount of space it uses.

so if you or anyone in the list can give me a clue on how to access the
actual value of a parameter from the local stack and calculate its size,
that would be a great help to me indeed.

thanks a lot,
Nemo

On Mon, Mar 29, 2010 at 5:42 AM, Eugene Kuleshov <[email protected]>wrote:

>
>  So you want to calculate something at runtime before method call and after
> the method call. For your scenario, primitive types are obvious and for a
> non-primitive types the easiest would be to write a static helper method,
> which you call for every parameter and non-primitive method return value.
> All param and return types you can retrieve from the called method signature
> and then generate code to call your static method. You may have to create
> some temporary variables in order to get the parameter values off the stack,
> but your transformation sould not change state of the stack at the point
> original method is called.
>
>  Hope that helps.
>
>  regards,
>  Eugene
>
>
>
> Nemo Caviani wrote:
>
>> Hello All,
>>
>> I am a newbie to ASM and I would appreciate your help with the following
>> matter.
>> I have load-time instrumented my bytecode. I keep all sorts of information
>> for my classes and methods to measure CPU time, memory usage, etc. Now, what
>> I need to do is to calculate the actual amount of data that is passed from
>> one method to another through the input parameters and also its return value
>> of the method.
>>
>> This is in particular important for me as it enables me to measure the
>> actual amount of data that arrays and link lists take when they are passed
>> as arguments to a method or when they are returned from methods.
>>
>> I have checked the visitLocalVariable method, but I am not sure how I can
>> relate the name and the description of a local variable to its actual data
>> size in the local stack memory, especially when it is not a basic type like
>> INT or BOOLEAN.
>>
>> I also looked into visitFrame which seems to have more details about the
>> variables of a method. However, overwriting visitFrame results in a
>> VerifyError as it seems like I need to calculate the stack size for the
>> method manually, which I don't know how.
>>
>> I highly appreciate any help from you guys.
>>
>> thanks a lot,
>> Nemo
>>
>
>
>
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