SourceReader.java

package lexer;

import java.io.*;
import java.util.ArrayList;

/**
 *  This class is used to manage the source program input stream;
 *  each read request will return the next usable character; it
 *  maintains the source column position of the character
*/
public class SourceReader {
    private BufferedReader source;
    //ArrayList for line-by-line access of source
    private static ArrayList<String> sourceLineList = new ArrayList<String>();   
    private int lineno = 0,   // line number of source program
        position;     // position of last character processed
    private boolean isPriorEndLine = true;  // if true then last character read was newline
                             // so read in the next line
    private String nextLine;

    /*
    public static void main(String args[]) {
        SourceReader s = null;
        try {
            s = new SourceReader("simple.x");
            while (true) {
                char ch = s.read();
                System.out.println("Char: " + ch + " Line: " + s.lineno +
                         "position: " + s.position);
            }
        } catch (Exception e) {}

        if (s != null) {
            s.close();
        }
    }
*/
    

/**
 *  Construct a new SourceReader
 *  @param sourceFile the String describing the user's source file
 *  @exception IOException is thrown if there is an I/O problem
*/
    public SourceReader(String sourceFile) throws IOException {
      //System.out.println("Source file: "+sourceFile);
    	//System.out.println("user.dir: " + System.getProperty("user.dir"));
        source = new BufferedReader(new FileReader(sourceFile));
        sourceLineList.add("DUMMY STRING");  //for zero index
    }

    void close() {
        try {
            source.close();
        } catch (Exception e) {}
    }

/**
 *  read next char; track line #, character position in line<br>
 *  return space for newline
 *  @return the character just read in
 *  @IOException is thrown for IO problems such as end of file
*/
    public char read() throws IOException {
        if (isPriorEndLine) {
            lineno++;
            position = -1;
            nextLine = source.readLine();
            if (nextLine != null) {
                System.out.println("READLINE:   "+nextLine);
                 //add line to ArrayList
                sourceLineList.add(nextLine);
            }
            isPriorEndLine = false;
        }
        if (nextLine == null) {  // hit eof or some I/O problem
            throw new IOException();
        }
        if ( nextLine.length() == 0) {
            isPriorEndLine = true;
            return ' ';
        }
        position++;
        if (position >= nextLine.length()) {
            isPriorEndLine = true;
            return ' ';
        }
       
        return nextLine.charAt(position);
    }

/**
 *  @return the position of the character just read in
*/
    public int getPosition() {
        return position;
    }

/**
 *  @return the line number of the character just read in
*/
    public int getLineno() {
        return lineno;
    }
    
/**
 *  prints the source file line-by-line, preceeded by line number
 *
*/
    public static void printSourceList() {
        int lineno;
        for(lineno = 1; lineno<sourceLineList.size(); lineno++) {
            System.out.println("" + lineno + ".   " + 
                    sourceLineList.get(lineno));
        }
    }
}