On Oct 17, 7:02 am, Michele <[EMAIL PROTECTED]> wrote:
> Hi,
> I write a simple encoder in python and Java; they do the same
> computations, with the same inputs
No they don't.
> however they won't produce the same
> output.
> Let me explain with code.
You have a strange understanding of the word "explain".
>
> First of all, you need a test file for input:
> $ dd if=/dev/urandom of=test.img bs=1048576 count=1
>
> I have attached the code.
> As you can see we have xor-red the same inputs (bitlists are the same,
> thus the selected blocks to xor are the same - you can easily see it,
> whenever a block is xor-red both programs will print out its hash).
> But here comes the strange: the random_block that the
> create_random_block function returns is not the same: in Java this block
> has an hash which is different from the Python one.
> Why?
>
> Thank you
>
> [test.py1K ]
> random_block = ['0']*blocksize
This initialises each element to '0'. ord('0') is 48, not 0. Either
I'm hallucinating, or I pointed this out to you in response to your
previous posting (within the last few days).
> random_block[j] = chr(ord(random_block[j]) ^
> ord(block[j]))
>
> [Test.java2K ]
> byte[] random_block = new byte[16384];
Presumably java initialises each element to 0 (or maybe random
gibberish); it is highly unlikely to be 48!
> random_block[j] = (byte)
> (random_block[j] ^ block[j]);
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