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 java.io.IOException;
020import java.io.InputStream;
021import java.util.Objects;
022
023import org.apache.commons.io.IOUtils;
024
025/**
026 * An {@link InputStream} that repeats provided bytes for given target byte count.
027 * <p>
028 * Closing this input stream has no effect. The methods in this class can be called after the stream has been closed
029 * without generating an {@link IOException}.
030 * </p>
031 *
032 * @see InfiniteCircularInputStream
033 * @since 2.8.0
034 */
035public class CircularInputStream extends InputStream {
036
037    /**
038     * Throws an {@link IllegalArgumentException} if the input contains -1.
039     *
040     * @param repeatContent input to validate.
041     * @return the input.
042     */
043    private static byte[] validate(final byte[] repeatContent) {
044        Objects.requireNonNull(repeatContent, "repeatContent");
045        for (final byte b : repeatContent) {
046            if (b == IOUtils.EOF) {
047                throw new IllegalArgumentException("repeatContent contains the end-of-stream marker " + IOUtils.EOF);
048            }
049        }
050        return repeatContent;
051    }
052
053    private long byteCount;
054    private int position = IOUtils.EOF;
055    private final byte[] repeatedContent;
056    private final long targetByteCount;
057
058    /**
059     * Constructs an instance from the specified array of bytes.
060     *
061     * @param repeatContent Input buffer to be repeated this buffer is not copied.
062     * @param targetByteCount How many bytes the read. A negative number means an infinite target count.
063     */
064    public CircularInputStream(final byte[] repeatContent, final long targetByteCount) {
065        this.repeatedContent = validate(repeatContent);
066        if (repeatContent.length == 0) {
067            throw new IllegalArgumentException("repeatContent is empty.");
068        }
069        this.targetByteCount = targetByteCount;
070    }
071
072    @Override
073    public int read() {
074        if (targetByteCount >= 0) {
075            if (byteCount == targetByteCount) {
076                return IOUtils.EOF;
077            }
078            byteCount++;
079        }
080        position = (position + 1) % repeatedContent.length;
081        return repeatedContent[position] & 0xff;
082    }
083
084}