    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}