001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.input;
018
019import static org.apache.commons.io.IOUtils.EOF;
020
021import java.io.IOException;
022import java.io.InputStream;
023
024import org.apache.commons.io.IOUtils;
025
026/**
027 * Always returns {@link IOUtils#EOF} to all attempts to read something from an input stream.
028 * <p>
029 * Typically uses of this class include testing for corner cases in methods that accept input streams and acting as a
030 * sentinel value instead of a {@code null} input stream.
031 * </p>
032 *
033 * @since 1.4
034 */
035public class ClosedInputStream extends InputStream {
036
037    /**
038     * The singleton instance.
039     *
040     * @since 2.12.0
041     */
042    public static final ClosedInputStream INSTANCE = new ClosedInputStream();
043
044    /**
045     * The singleton instance.
046     *
047     * @deprecated Use {@link #INSTANCE}.
048     */
049    @Deprecated
050    public static final ClosedInputStream CLOSED_INPUT_STREAM = INSTANCE;
051
052    /**
053     * Returns {@link #INSTANCE} if the given InputStream is null, otherwise returns the given input stream.
054     *
055     * @param in the InputStream to test.
056     * @return {@link #INSTANCE} if the given InputStream is null, otherwise returns the given input stream.
057     */
058    static InputStream ifNull(final InputStream in) {
059        return in != null ? in : INSTANCE;
060    }
061
062    /**
063     * Returns -1 to indicate that the stream is closed.
064     *
065     * @return always -1
066     */
067    @Override
068    public int read() {
069        return EOF;
070    }
071
072    /**
073     * Returns -1 to indicate that the stream is closed.
074     *
075     * @param b ignored.
076     * @param off ignored.
077     * @param len ignored.
078     * @return always -1
079     */
080    @Override
081    public int read(final byte[] b, final int off, final int len) throws IOException {
082        return EOF;
083    }
084
085}