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parsing a short into 2 pieces

7 replies on 1 page. Most recent reply: Nov 13, 2003 1:19 AM by Senthoorkumaran Punniamoorthy

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Tanya

Posts: 16
Nickname: seabeck
Registered: Nov, 2003

parsing a short into 2 pieces Posted: Nov 1, 2003 5:56 PM
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I have an array of shorts and I need to parse the value in one of the fields into 2 parts. For instance shtVal[2] = 20. I need to get the 2 and then I need to get the 0 by themselves. I created a method that does the first part by using int val = shtVal[2];
val <<= 8;

This seems to work correctly but when I try to shift it right by doing
val >>= 8; It gives me the incorect value.

Thanks for any help you may provide.


Senthoorkumaran Punniamoorthy

Posts: 335
Nickname: senthoor
Registered: Mar, 2002

Re: parsing a short into 2 pieces Posted: Nov 1, 2003 5:59 PM
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Why don't you post your code what you have now?

Tanya

Posts: 16
Nickname: seabeck
Registered: Nov, 2003

Re: parsing a short into 2 pieces Posted: Nov 1, 2003 6:04 PM
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Here is my code I am simulating computer memory IR stands for instruction register. We are using hex values for our instructions.

private int getR1() //this is for getting the first value
{
int r1 = reg.getIR(1);
r1 <<= 8;
r1 = (r1 / 0x1000);//convert hex value to int.
return r1;
}

private int getR2()
{
int r2 = reg.getIR(1);
r2 >>= 8;
//r2 = (r2 / 0x1000);
return r2;
}

Senthoorkumaran Punniamoorthy

Posts: 335
Nickname: senthoor
Registered: Mar, 2002

Re: parsing a short into 2 pieces Posted: Nov 1, 2003 6:23 PM
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> I created a method that does the first part
> by using int val = shtVal[2];
> val <<= 8;

Sorry to ask this again. I am little confuced with your problem. say you have an int array

int test[] ={10,20,30};

then your code is suppose to take these values and produce and output.

Please explain me what the output should look like in detail. What I understand now is if you have the first value 10 basically you want to separate it into 1 and 0 and the next 20 to 2 and 0. Am I right? Please correct me if I am wrong?

Tanya

Posts: 16
Nickname: seabeck
Registered: Nov, 2003

Re: parsing a short into 2 pieces Posted: Nov 1, 2003 9:06 PM
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Yes what I have now is an array of shorts that contain hexcidecimal values.
I am simulating a simple computer and I am loading an .obj file to the memory of the simple computer.
I have to use those opcodes to do simple tasks.

The array represents a 4 part instruction register and the second index contains a register to pass things to and a register to get things from.
For example I have int temp = IR[1]; temp might have a hexadecimal value of 21 and what I need to do is seperate the 2 and the 1.

I have to remember that they are hexadecimal rather than decimal values. That is why in the first method I had to / by 0x1000. I don't understand why this works but it does.

what I am having problems with is that I need to get the 1. and I tried to do the same but with reversed >> operands. What I always get is 0 for the answer which is the wrong answer.

Senthoorkumaran Punniamoorthy

Posts: 335
Nickname: senthoor
Registered: Mar, 2002

Re: parsing a short into 2 pieces Posted: Nov 2, 2003 7:57 PM
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WHy don't you use / and % operaters to get the same results?
    System.out.println(0x34);
        System.out.println(0x34 / 16);
        System.out.println(0x34 % 16);


Wouldn't that help you?

Tanya

Posts: 16
Nickname: seabeck
Registered: Nov, 2003

Re: parsing a short into 2 pieces Posted: Nov 12, 2003 11:48 PM
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Thank you for your help, I actually used a slightly different version that rather than dividing by 16 I shift the bit by 4 which is the same thing because it basically is 2^4 = 16. Here is my final code that I used. 

private int getR1()
{
      int r1=((reg.getIR(1) &0xF0));
      r1 >>= 4;
      return r1;
}
 
private int getR2()
{
      int r2= reg.getIR(1);
      r2 = r2&0xF;
      return r2;
}

Senthoorkumaran Punniamoorthy

Posts: 335
Nickname: senthoor
Registered: Mar, 2002

Re: parsing a short into 2 pieces Posted: Nov 13, 2003 1:19 AM
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Thanks for letting us know the results

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