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any java lib can decode x86 cpu instruction

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  any java lib can decode x86 cpu instruction Peter <mcheung63@gmail.com> - 2014-07-01 01:55 +0800
    Re: any java lib can decode x86 cpu instruction Roedy Green <see_website@mindprod.com.invalid> - 2014-06-30 16:48 -0700
      Re: any java lib can decode x86 cpu instruction Peter <mcheung63@gmail.com> - 2014-07-02 01:10 +0800
        Re: any java lib can decode x86 cpu instruction Roedy Green <see_website@mindprod.com.invalid> - 2014-07-02 09:37 -0700
    Re: any java lib can decode x86 cpu instruction "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-14 12:18 +0100

#28878 — any java lib can decode x86 cpu instruction

any java lib can decode x86 cpu instruction?

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#28880

On Tue, 01 Jul 2014 01:55:03 +0800, Peter <mcheung63@gmail.com> wrote,
quoted or indirectly quoted someone who said :

>any java lib can decode x86 cpu instruction?

The JVM in written at the lowest level in X86 CPU instructions, so
when it runs, such code is decoded, but doubt that is what you are
asking.

Are you looking for a disassembler?

Are you asking is it possible to integrate X86 assembler code into
Java?  See http://mindprod.com/jgloss/jni.html


-- 
Roedy Green Canadian Mind Products http://mindprod.com
A program is only as good as its worst piece of code.
~ Joshua Cramer

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#28886

於 1/7/14上午7:48, Roedy Green 提到:
> On Tue, 01 Jul 2014 01:55:03 +0800, Peter <mcheung63@gmail.com> wrote,
> quoted or indirectly quoted someone who said :
>
>> any java lib can decode x86 cpu instruction?
>
> The JVM in written at the lowest level in X86 CPU instructions, so
> when it runs, such code is decoded, but doubt that is what you are
> asking.
>
> Are you looking for a disassembler?
>
> Are you asking is it possible to integrate X86 assembler code into
> Java?  See http://mindprod.com/jgloss/jni.html
>
>

I am looking for a x86 disassembler in java

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#28908

On Wed, 02 Jul 2014 01:10:57 +0800, Peter <mcheung63@gmail.com> wrote,
quoted or indirectly quoted someone who said :

>I am looking for a x86 disassembler in java

I wrote my own assembler years for 16 bit 8086 apps.  At the time
VTech had a 16-bit disassembler. I also used Periscope which let me
trace and disassemble. I used them to help verify my work.  Both
disappeared, and I was never able to find a 32 or 64-bit disassembler
written in any language.

The Intel instruction set is difficult to disassemble. You have to do
a lot of guessing. You can't even tell for certain if something is
instructions or data. 

The Motorola chips, in contrast, were ever so much simpler.

Very few people actually write any assembler any more:
C compiler writers, Jet Java compiler optimisers. It is generated by
programs. At one point Jet could be persuaded to show me an assembler
listing of its generated code.  I was astounded to discover it did
better than my best hand-generated code where I calculated the cycles
for every instruction and did all-possibilities analysis. It considers
pipelines and does versioning too. Writing assembler code is now, like
chess, best left to machines.

There are of course Java decompilers and disassemblers, that work on
class files.  Java is REALLY easy to decompile.
http://mindprod.com/jgloss/decompiler.html
-- 
Roedy Green Canadian Mind Products http://mindprod.com
A program is only as good as its worst piece of code.
~ Joshua Cramer

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#29094

Peter wrote:

> any java lib can decode x86 cpu instruction?

When I needed just that some years ago I looked but couldn't find anything I 
could use (can't remember now if I found nothing or only things with 
incompatible licences).

But there are /lots/ of x86 dissemblers written in C/C++, with many different 
licences, so I just wrapped one of those.

(In my case I embedded it as a callable library, but I suspect that it would 
often be sufficient to invoke it as an external program.)

    -- chris 

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