PasswordField.java

/*
 * Copyright 2011 Jesper Terkelsen.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * 
 */
package dk.deck.remoteconsole.input;

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

/**
 * This class prompts the user for a password and attempts to mask input with
 * "*"
 * @author Jesper Terkelsen
 */
public class PasswordField {

    /**
     * @param input stream to be used (e.g. System.in)
     * @param output stream to be used (e.g. System.out)
     * @param prompt The prompt to display to the user.
     * @return The password as entered by the user.
     */
    public static char[] getPassword(InputStream in, PrintStream output, String prompt) throws IOException {
        MaskingThread maskingthread = new MaskingThread(prompt, output);
        Thread thread = new Thread(maskingthread);
        thread.start();

        char[] lineBuffer;
        char[] buf;
        int i;

        buf = lineBuffer = new char[128];

        int room = buf.length;
        int offset = 0;
        int c;

        loop:
        while (true) {
            switch (c = in.read()) {
                case -1:
                case '\n':
                    break loop;

                case '\r':
                    int c2 = in.read();
                    if ((c2 != '\n') && (c2 != -1)) {
                        if (!(in instanceof PushbackInputStream)) {
                            in = new PushbackInputStream(in);
                        }
                        ((PushbackInputStream) in).unread(c2);
                    } else {
                        break loop;
                    }

                default:
                    if (--room < 0) {
                        buf = new char[offset + 128];
                        room = buf.length - offset - 1;
                        System.arraycopy(lineBuffer, 0, buf, 0, offset);
                        Arrays.fill(lineBuffer, ' ');
                        lineBuffer = buf;
                    }
                    buf[offset++] = (char) c;
                    break;
            }
        }
        maskingthread.stopMasking();
        if (offset == 0) {
            return null;
        }
        char[] ret = new char[offset];
        System.arraycopy(buf, 0, ret, 0, offset);
        Arrays.fill(buf, ' ');
        return ret;
    }
}