EOLConvertingInputStream: InputStream which converts \r bytes not followed by \n and \n not preceded by \r to \r\n. : InputStream « File « Java Tutorial

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import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;

/**
 * InputStream which converts <code>\r</code>
 * bytes not followed by <code>\n</code> and <code>\n</code> not 
 * preceded by <code>\r</code> to <code>\r\n</code>.
 */
public class EOLConvertingInputStream extends InputStream {
    /** Converts single '\r' to '\r\n' */
    public static final int CONVERT_CR   = 1;
    /** Converts single '\n' to '\r\n' */
    public static final int CONVERT_LF   = 2;
    /** Converts single '\r' and '\n' to '\r\n' */
    public static final int CONVERT_BOTH = 3;
    
    private PushbackInputStream in = null;
    private int previous = 0;
    private int flags = CONVERT_BOTH;
    
    /**
     * Creates a new <code>EOLConvertingInputStream</code>
     * instance converting bytes in the given <code>InputStream</code>.
     * The flag <code>CONVERT_BOTH</code> is the default.
     * 
     * @param in the <code>InputStream</code> to read from.
     */
    public EOLConvertingInputStream(InputStream in) {
        this(in, CONVERT_BOTH);
    }
    /**
     * Creates a new <code>EOLConvertingInputStream</code>
     * instance converting bytes in the given <code>InputStream</code>.
     * 
     * @param in the <code>InputStream</code> to read from.
     * @param flags one of <code>CONVERT_CR</code>, <code>CONVERT_LF</code> or
     *        <code>CONVERT_BOTH</code>.
     */
    public EOLConvertingInputStream(InputStream in, int flags) {
        super();
        
        this.in = new PushbackInputStream(in, 2);
        this.flags = flags;
    }

    /**
     * Closes the underlying stream.
     * 
     * @throws IOException on I/O errors.
     */
    @Override
    public void close() throws IOException {
        in.close();
    }
    
    /**
     * @see java.io.InputStream#read()
     */
    @Override
    public int read() throws IOException {
        int b = in.read();
        
        if (b == -1) {
            return -1;
        }
        
        if ((flags & CONVERT_CR) != 0 && b == '\r') {
            int c = in.read();
            if (c != -1) {
                in.unread(c);
            }
            if (c != '\n') {
                in.unread('\n');
            }
        } else if ((flags & CONVERT_LF) != 0 && b == '\n' && previous != '\r') {
            b = '\r';
            in.unread('\n');
        }
        
        previous = b;
        
        return b;
    }

}