001/*
002 * CDDL HEADER START
003 *
004 * The contents of this file are subject to the terms of the
005 * Common Development and Distribution License, Version 1.0 only
006 * (the "License").  You may not use this file except in compliance
007 * with the License.
008 *
009 * You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
010 * or http://forgerock.org/license/CDDLv1.0.html.
011 * See the License for the specific language governing permissions
012 * and limitations under the License.
013 *
014 * When distributing Covered Code, include this CDDL HEADER in each
015 * file and include the License file at legal-notices/CDDLv1_0.txt.
016 * If applicable, add the following below this CDDL HEADER, with the
017 * fields enclosed by brackets "[]" replaced with your own identifying
018 * information:
019 *      Portions Copyright [yyyy] [name of copyright owner]
020 *
021 * CDDL HEADER END
022 *
023 *
024 *      Copyright 2008 Sun Microsystems, Inc.
025 *      Portions Copyright 2015 ForgeRock AS
026 */
027
028package org.opends.quicksetup.util;
029
030import java.io.OutputStream;
031import java.io.IOException;
032import java.io.PrintStream;
033
034/**
035 * Tool for suppressing and unsuppressing output to standard
036 * output streams.
037 */
038public class StandardOutputSuppressor {
039
040  private static Token token;
041
042  /** Object to return to this class for unsuppressing output. */
043  private static class Token {
044    PrintStream out;
045    PrintStream err;
046  }
047
048  /** Suppresses output to the standard output streams. */
049  public static synchronized void suppress() {
050    if (token == null) {
051      token = new Token();
052      token.out = System.out;
053      token.err = System.err;
054      System.out.flush();
055      System.err.flush();
056      System.setOut(new PrintStream(new NullOutputStream()));
057      System.setErr(new PrintStream(new NullOutputStream()));
058    } else {
059      throw new IllegalStateException("Standard streams currently suppressed");
060    }
061  }
062
063  /**
064   * Unsuppresses the standard output streams.  Following a call to this
065   * method System.out and System.err will point to the descriptor prior
066   * to calling <code>suppress()</code>.
067   */
068  public static synchronized void unsuppress() {
069    if (token != null) {
070      System.setOut(token.out);
071      System.setErr(token.err);
072      token = null;
073    } else {
074      throw new IllegalStateException(
075              "Standard streams not currently suppressed");
076    }
077  }
078
079  /**
080   * Checks whether or not this class has suppressed standard out streams.
081   * @return boolean where true indicates output is suppressed
082   */
083  public static boolean isSuppressed() {
084    return token != null;
085  }
086
087  /**
088   * PrintWriter for suppressing stream.
089   */
090  private static class NullOutputStream extends OutputStream {
091
092    /** {@inheritDoc} */
093    public void write(int b) throws IOException {
094      // do nothing;
095    }
096  }
097}