/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 org.apache.commons.compress.utils;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

A wrapper that overwrites skip and delegates to FilterInputStream.read instead. 
Some implementations of InputStream implement InputStream.skip in a way that throws an exception if the stream is not seekable - 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 discard the data read) instead. Skipping is potentially much faster than reading so we do want to invoke skip when possible. We provide this class so you can wrap your own InputStream in it if you encounter problems with skip throwing an excpetion.
Since:
1.17/**
 * A wrapper that overwrites {@link #skip} and delegates to {@link #read} instead.
 *
 * <p>Some implementations of {@link InputStream} implement {@link
 * InputStream#skip} in a way that throws an exception if the stream
 * is not seekable - {@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 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
 * you can wrap your own {@link InputStream} in it if you encounter
 * problems with {@code skip} throwing an excpetion.</p>
 *
 * @since 1.17
 */
public class SkipShieldingInputStream extends FilterInputStream {
    private static final int SKIP_BUFFER_SIZE = 8192;
    // we can use a shared buffer as the content is discarded anyway
    private static final byte[] SKIP_BUFFER = new byte[SKIP_BUFFER_SIZE];
    public SkipShieldingInputStream(InputStream in) {
        super(in);
    }

    @Override
    public long skip(long n) throws IOException {
        return n < 0 ? 0 : read(SKIP_BUFFER, 0, (int) Math.min(n, SKIP_BUFFER_SIZE));
    }
}