LineNumberPrintWriter.java

package org.jboss.windup.decompiler.procyon;

import java.io.PrintWriter;
import java.io.Writer;
import java.util.Arrays;

/**
 * FIXME - This source file requires its original license and credits for original authors.
 * 
 * A specialization of {@link PrintWriter} which can automatically prefix lines with a Java-commented, justified line
 * number. This class overrides only the {@link #print(String)} and {@link #println(String)} methods, therefore all
 * other methods must be avoided.
 */
class LineNumberPrintWriter extends PrintWriter
{
    public static final int NO_LINE_NUMBER = -1;
    private final String _emptyPrefix;
    private final String _format;
    private boolean _needsPrefix;
    private boolean _suppressLineNumbers;

    /**
     * Creates an instance. The only valid "print" methods to call are {@link #print(String)} and
     * {@link #println(String)}.
     * 
     * @param maxLineNo the highest line number that 'this' will ever encounter
     * @param w the underlying {@link Writer} to which characters are printed.
     */
    public LineNumberPrintWriter(int maxLineNo, Writer w)
    {
        super(w);
        String maxNumberString = String.format("%d", maxLineNo);
        int numberWidth = maxNumberString.length();
        _format = "/*%" + numberWidth + "d*/";
        String samplePrefix = String.format(_format, maxLineNo);
        char[] prefixChars = samplePrefix.toCharArray();
        Arrays.fill(prefixChars, ' ');
        _emptyPrefix = new String(prefixChars);
        _needsPrefix = true;
    }

    /**
     * Causes 'this' printer to not emit any line numbers or any whitespace padding.
     */
    public void suppressLineNumbers()
    {
        _suppressLineNumbers = true;
    }

    @Override
    public void print(String s)
    {
        this.print(NO_LINE_NUMBER, s);
    }

    @Override
    public void println(String s)
    {
        this.println(NO_LINE_NUMBER, s);
    }

    public void println(int lineNumber, String s)
    {
        this.doPrefix(lineNumber);
        super.println(s);
        _needsPrefix = true;
    }

    public void print(int lineNumber, String s)
    {
        this.doPrefix(lineNumber);
        super.print(s);
    }

    private void doPrefix(int lineNumber)
    {
        if (_needsPrefix && !_suppressLineNumbers)
        {
            if (lineNumber == NO_LINE_NUMBER)
            {
                super.print(_emptyPrefix);
            }
            else
            {
                String prefix = String.format(_format, lineNumber);
                super.print(prefix);
            }
        }
        _needsPrefix = false;
    }
}