Steer Clear, Binary in here

[killgORE]

Feeling like a dumb ass. But thinkning in binary has never been my strong suit. The problem is I have to write a java prog that spits out a series of bytes - to "AN" output stream. This is fine. WriteBytes(x) would suffice. My problem is getting the correct definition of data inside x.

x is probably going to be a byte array (or whatever if you guys can suggest something better). x[0] has to be = 0x47 in hex. So this part is fine. The place where - for some reason - my head waves a flag is at x[1]. At this point I need to define only 3 binary digits - which are flags. Then the start of a 13 bit address (so only the first 5 bits of this are in x[1] then rest are in x[2]).

How ?? Do you write in binary in java ? It really appears as though it is hidden VERY well.

[Mart]

Have a look at the bit shift operators (>>>,>> and <) for moving bits around and and the bitwise OR operator( |) for combining values.

[killgORE]

I have played about with those bitwise operators a 'bit' back (excuse that little pun, keeps me amused).

I believe my thinking has become too obscure for this problem... I know that in my mind I think of the data as 3 bits (flags) followed by 13 bits (addressing). What this equates to is 2 entries in the byte array (3+13 = 16). So I just don't know what to do because the flags are variable.

How to combine these ?

I have knocked up some code for printing out a string representation of a given byte or integer. So I can see how the shifting moves the 1's....

[Mart]

Heres an example, syntax may be incorrect because I'm a c++ programmer not a Java programmer...

short sAddress = 0x1234; // Var to hold 13 bit address just fill bottom 13 bits)
short sBytes = 0; // var to hold 2 bytes to write to stream

// Copy the address to the bottom 13 bits
sBytes = nAddress & 0x1FFF;

// Set each flag to 1 as necessary, omit for 0
sBytes |= 0x2000 // Set bit 13 to 1
sBytes |= 0x4000 // Set bit 14 to 1
sBytes |= 0x8000 // Set bit 15 to 1

// Append the data to the stream object
DataOutputStream dos;
dos.writeByte(0x47);
dos.writeShort(sBytes);

.. keep on appending the bytes, shorts or ints until you have finished.

Obviously you dont need sAddress and sBytes, I did this to make it easier to comprehend.

Mart

[Mart]

Now without the typos...

Heres an example, syntax may be incorrect because I'm a c++ programmer not a Java programmer...

short sAddress = 0x1234; // Var to hold 13 bit address just fill bottom 13 bits
short sBytes = 0; // var to hold 2 bytes to write to stream

// Copy the address to the bottom 13 bits
sBytes = sAddress & 0x1FFF;

// Set each flag to 1 as necessary, omit for 0
sBytes |= 0x2000 // Set bit 13 to 1
sBytes |= 0x4000 // Set bit 14 to 1
sBytes |= 0x8000 // Set bit 15 to 1

// Append the data to the stream object
DataOutputStream dos;
dos.writeByte(0x47);
dos.writeShort(sBytes);

.. keep on appending the bytes, shorts or ints until you have finished.

Obviously you dont need sAddress and sBytes, I did this to make it easier to comprehend.

Mart

[killgORE]

I hacked that code into java... flung it through my lovely numbers to String method... And it pumped out this. Assuming that sAddress = 0x1234.

00000000 00000000 00000000 01000111 //0x47
00000000 00000000 00010010 00110100 //sAddress & 0x1FFF
00000000 00000000 00110010 00110100 //sBytes | 0x2000
00000000 00000000 01110010 00110100 //sBytes | 0x4000
00000000 00000000 11110010 00110100 //sBytes | 0x8000

Whenever I am satisfied with what I get... I will trust it to just write the bytes somewhere. But I personally can't read those lovely object memory addresses that get spat out... They are not for human consumption. Just the JVM.

p.s. you can edit your messages on these boards ! Rather than make another post... bottom right corner of your 'box'

[Mart]

Your last post is a little confusing? The binary looks fine to me.

I'm not trying to be funny but do you understand how to convert from hex to binary + vice versa?

Mart

[killgORE]

yes.... That was just for your information ! I am at a point where I should be able to run with this prog... It is nothing major.

My proper project is the reverse of the problem. Where I read in this data (2,805,000 188byte packets worth) and perform some tricks and magic.

What made you think i can't read binary... is it this ?
" I personally can't read those lovely object memory addresses that get spat out.."

Java spits out its horrible representation of an object if you ask it to.

[Mart]

Yep " I personally can't read those lovely object memory addresses that get spat out.." was the one.

Good to hear your sorted now.

Thanks for the edit tip. I did try to edit my post by pressing the button above my post couldn't understand why I was getting permission denied...doh!

Mart

[malfunction]

Originally posted by Mart
Yep " I personally can't read those lovely object memory addresses that get spat out.." was the one.

Good to hear your sorted now.

Thanks for the edit tip. I did try to edit my post by pressing the button above my post couldn't understand why I was getting permission denied...doh!

Mart

You need to use the edit button *below* your post.

[Mart]

Yep, I figured that out hence the doh! Its taken me long enough though

[malfunction]

Originally posted by Mart
Yep, I figured that out hence the doh! Its taken me long enough though

Erm... Well allow me to say:

Doh!

too...

[killgORE]

D'ho.... Like a pair of clean undies. I felt left out.