001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.commons.compress.utils;
020
021import java.io.FilterInputStream;
022import java.io.IOException;
023import java.io.InputStream;
024
025/**
026 * A wrapper that overwrites {@link #skip} and delegates to {@link #read} instead.
027 *
028 * <p>
029 * Some implementations of {@link InputStream} implement {@link InputStream#skip} in a way that throws an exception if the stream is not seekable -
030 * {@link System#in System.in} is known to behave that way. For such a stream it is impossible to invoke skip at all and you have to read from the stream (and
031 * discard the data read) instead. Skipping is potentially much faster than reading so we do want to invoke {@code skip} when possible. We provide this class so
032 * you can wrap your own {@link InputStream} in it if you encounter problems with {@code skip} throwing an exception.
033 * </p>
034 *
035 * @since 1.17
036 * @deprecated No longer used.
037 */
038@Deprecated
039public class SkipShieldingInputStream extends FilterInputStream {
040
041    private static final int SKIP_BUFFER_SIZE = 8192;
042
043    /** We can use a shared buffer as the content is discarded anyway. */
044    private static final byte[] SKIP_BUFFER = new byte[SKIP_BUFFER_SIZE];
045
046    /**
047     * Creates a {@code SkipShieldingInputStream} by assigning the argument {@code in} to the field {@code this.in} so as to remember it for later use.
048     *
049     * @param in the underlying input stream, or {@code null} if this instance is to be created without an underlying stream.
050     */
051    public SkipShieldingInputStream(final InputStream in) {
052        super(in);
053    }
054
055    @Override
056    public long skip(final long n) throws IOException {
057        return n < 0 ? 0 : read(SKIP_BUFFER, 0, (int) Math.min(n, SKIP_BUFFER_SIZE));
058    }
059}