SkipShieldingInputStream.java

/*
 * 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
 *
 *   https://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 {@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 exception.
 * </p>
 *
 * @since 1.17
 * @deprecated No longer used.
 */
@Deprecated
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];

    /**
     * Creates a {@code SkipShieldingInputStream} by assigning the argument {@code in} to the field {@code this.in} so as to remember it for later use.
     *
     * @param in the underlying input stream, or {@code null} if this instance is to be created without an underlying stream.
     */
    public SkipShieldingInputStream(final InputStream in) {
        super(in);
    }

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