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Assembler

Posted on 2009-07-10
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Last Modified: 2012-05-07
This is basically about assembler (.java) for reading a define file that has extension (.src) and writing it or the output is file extension is (.xxx)... The Assembler has a role during the execuation which are:
1- Invalid opcode
2- Missing opcode
3- Illegal comment
4- Illegal constant
5- Illegal memory address.

I have done so far number 1. 3 and 5 but i want to develop my code and do 2- Missing opcode and 4- Illegal constant...

The code is show below and the main running code is attached
import java.util.Scanner;
import java.lang.String;
 
class Code
{
	private String opcodeSource;
	private String comment;
	private int operand;
	private int opcode;
	private Boolean errorStatus = false;
	private String errorMessage;
	public Code(String codeLine)
	{
		Scanner in = new Scanner(codeLine);
 
		opcodeSource = in.next().trim();
 
		if(!opcodeSource.toLowerCase().equals("stop"))
		{
			if(!opcodeSource.equals(" "))
			{
 
				opcode = inputDecoder(opcodeSource);
				try // this try-catch block is supposed to catch missing opcode but it does not work properly
				{
					operand = in.nextInt();
					comment = in.nextLine().trim();
				}
				catch (Exception e)
				{
					opcodeSource = " ";
					String junk = in.nextLine();
					System.out.println(junk);
					errorStatus = true;
					errorMessage ="Missing opcode";
				}
 
			}
		}
		else  // if opcode is STOP
		{
			operand = 0;
			comment = "; end program";
			opcode = 15;
		}
		if(opcode == 12)  // checks for invalid opcode
		{
			errorStatus = true;
			errorMessage = "Invalid opcode";
		}
		if(!comment.startsWith(";")) //checks for illegal comments
		{
			errorStatus = true;
			errorMessage = "Illegal comment";
		}
		if(opcode == 1 | opcode == 2 | opcode == 3 | opcode == 4 ) // checks for illegal memory address
		{
			if(operand < 0)
			{
				errorStatus = true;
				errorMessage = "Illegal memory address";
			}
		}
	}
 
	public void setOperand(int opcode)
	{
		this.opcode = opcode;
	}
 
	public Boolean getErrorStatus()
	{
		return errorStatus;
	}
 
	public String getErrorMessage()
	{
		return errorMessage;
	}
 
	public String getOpcodeSource()
	{
		return opcodeSource;
	}
 
	public int getOperand()
	{
		return operand;
	}
 
	public String getComment()
	{
		return comment;
	}
 
	public int getOpcode()
	{
		return opcode;
	}
 
	public int inputDecoder(String temp)
	{
		int result;
		temp = temp.toLowerCase();
 
		if(temp.equals("nop"))
			result = 0;
 
		else if(temp.equals("load"))
			result = 1;
 
		else if(temp.equals("store"))
			result = 2;
 
		else if(temp.equals("add"))
			result = 3;
 
		else if(temp.equals("sub"))
			result = 4;
 
		else if(temp.equals("loadi"))
			result = 5;
 
		else if(temp.equals("addi"))
			result = 6;
 
		else if(temp.equals("subi"))
			result = 7;
 
		else if(temp.equals("brz"))
			result = 8;
 
		else if(temp.equals("brn"))
			result = 9;
 
		else if(temp.equals("brp"))
			result = 10;
 
		else if(temp.equals("bra"))
			result = 11;
 
		else if(temp.equals("trap"))
			result = 14;
 
		else if(temp.equals("stop"))
			result = 15;
 
		else
			result = 12;
 
		return result;
	}
}

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Question by:adam_prog
  • 7
  • 6
13 Comments
 
LVL 86

Expert Comment

by:CEHJ
ID: 24829752
Please give examples of good input and bad input
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Author Comment

by:adam_prog
ID: 24829901
i have attached the example
0
 

Author Comment

by:adam_prog
ID: 24829903
read the file that has exension .src  and the date contains in that file as following way:

LOADI      0
STORE      499
TRAP      0
STORE      498
LOAD      498
SUBI      0
BRP      2
BRA      14
LOAD      499
ADD       498
STORE       499
LOAD      498
SUBI      1
STORE      498
BRA      -22
LOAD      499
TRAP      1
STOP      0
0
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LVL 86

Expert Comment

by:CEHJ
ID: 24829978
>>i have attached the example

Nope - all you attached was a small app concerned with RMARepair.

So you've just posted a good sample. What bad sample are you trying to protect against?
0
 

Author Comment

by:adam_prog
ID: 24829983
bad example if the opcode is missing should print option 1- Invalid opcode
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LVL 86

Expert Comment

by:CEHJ
ID: 24829995
Because you're using a Scanner and because of its default delimiters, that's relatively tricky - you'll only find a missing int code when you try to parse an instruction (since the number is missing) as an int.

I would be inclined to read lines and split into a 2-element array. You can then count the elements and take action if < 2 and !stop
0
 

Author Comment

by:adam_prog
ID: 24830010
can you code it or what my code should be?
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 24830028
Essentially just:
in.useDelimiter("[\r\n]");
...
 
String[] instAndOpCode = in.nextLine().split("\\s+");

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Author Comment

by:adam_prog
ID: 24830035
how the array could be done
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LVL 86

Expert Comment

by:CEHJ
ID: 24839451
You'll find it even easier using this:

http://technojeeves.com/joomla/index.php/free/74-string-list

>>how the array could be done

Check the element count - it will tell you if the opcode is missing (or at least either instruction or opcode)
0
 

Author Comment

by:adam_prog
ID: 24899938
I tried to put the array but it still only print one line... I only want to print or write the all content on the file... as anyone can help or can fix my code...i appreciate... thanks.. here is the code

import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;
class CSE340Project1
{
 
	public static void main(String args[])
	{
		ArrayList inputList= new ArrayList();
		String filename,line,fileToSave;
		Boolean check = false;
		Boolean cont = false;
		Scanner scan = new Scanner(System.in);
 
 
					
		System.out.println("Enter the file name");
		filename = scan.next();
		//filename BufferReader.next();
		filename = filename.toLowerCase();
 
		try
		{
			check = checkFilename(filename);
			cont = true;
		}
		catch(Exception e)
		{
			System.out.println("Assembily not complete - Illegal file name");
		}
		if(cont)
		{
			try
			{
				
				FileInputStream fstream = new FileInputStream(filename);
				BufferedReader readLine = new BufferedReader (new InputStreamReader(System.in));
				DataInputStream in = new DataInputStream(fstream);
				int count = 0;
				//line = in.readLine();
				//count++;
				while ( in.available() !=0)
				{
					line = in.readLine();
					//inputList.add(new Code(line));
						
					String line1[]= line.split("\\s+");
					count++;
				}
 
				in.close();
		        
			}
			
			catch (Exception e)
			
			{
				System.err.println("Assembily not complete - File does not exist");
				cont = false;
			}
			if(cont)
			{
				fileToSave = filename.replace(".src",".");
				cont = createListingFile(inputList,fileToSave);
				cont =	createExecutableFile(inputList,fileToSave);
			}
			if(cont)
			{
				System.out.println("Assembly complete. No errors");
			}
 
		}
	}
 
	public static Boolean createListingFile(ArrayList list, String fileToSave)
	{
		FileOutputStream out; 			// declare a file output object
		PrintStream p; 					// declare a print stream object
		int lineCount = 0;
		Boolean result = true;
 
		try
		{
			// Create a new file output stream
			out = new FileOutputStream(fileToSave + "lis");
 
			// Connect print stream to the output stream
			p = new PrintStream( out );
 
			//p.println ("This is written to a file");
			p.println("Loc\tOpCode\tOperand");
			for(int index = 0; index < list.size(); index++)
			{
				Code temp = (Code)list.get(index);
				lineCount++;
				//prints one line for current code object
				p.println(2*index+"\t"+temp.getOpcode()+"\t"+temp.getOperand()+"\t"+
				(index+1)+".\t"+temp.getOpcodeSource()+"\t"+temp.getOperand()+"\t"+
				temp.getComment());
				if(temp.getErrorStatus())
				{
					p.println("Error: "+temp.getErrorMessage());
					System.out.print("Error: "+temp.getErrorMessage()+"\nOccured at line number: "+lineCount+"\n");
					throw new Exception();
				}
			}
			p.close();
 
		}
		catch (Exception e)
		{
			System.err.println ("Assembily error");
			result = false;
		}
		return result;
	}
	public static Boolean createExecutableFile(ArrayList list, String fileToSave)
	{
 
		FileOutputStream out; // declare a file output object
		PrintStream p; // declare a print stream object
		int lineCount = 0;
		Boolean result = true;
 
		try
		{
			// Create a new file output stream
			out = new FileOutputStream(fileToSave + "xxx");
 
			// Connect print stream to the output stream
			p = new PrintStream( out );
 
			for(int index = 0; index < list.size(); index++)
			{
				Code temp = (Code)list.get(index);
				lineCount++;
				if(temp.getErrorStatus())
				{
					System.out.print("Error: "+temp.getErrorMessage()+"\nOccured at line number: "+lineCount+"\n");
					throw new Exception();
				}
				else
				{
					p.println(temp.getOpcode());
					p.println(temp.getOperand());
				}
			}
			//p.println ("This is written to a file");
			p.close();
 
		}
		catch (Exception e)
		{
			System.err.println ("Assembily error");
			result = false;
		}
		return result;
	}
	public static Boolean checkFilename(String filename) throws Exception
	{
		Boolean result = false;
		if(filename.endsWith(".src"))
			result = true;
		else
			throw new Exception();
		return result;
	}
}

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LVL 86

Accepted Solution

by:
CEHJ earned 500 total points
ID: 24902079
Replace

>>
        FileInputStream fstream = new FileInputStream(filename);
        BufferedReader readLine = new BufferedReader(new InputStreamReader(
                    System.in));
        DataInputStream in = new DataInputStream(fstream);
        int count = 0;

        //line = in.readLine();
        //count++;
        while (in.available() != 0) {
            line = in.readLine();

            //inputList.add(new Code(line));
            String[] line1 = line.split("\\s+");
            count++;
        }

        in.close();
>>

by
        BufferedReader readLine = new BufferedReader(new FileReader(filename));
        int count = 0;
        String line = null;
        while ((line = in.readLine()) != null) {
            String[] line1 = line.split("\\s+");
            count++;
            System.out.printf("Number of tokens on line %d is %d\n", count, line1.length);
        }
        in.close();

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Author Closing Comment

by:adam_prog
ID: 31602366
very good
0

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