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 *
027 * An {@link InputStream} that repeats provided bytes for given target byte count.
028 * <p>
029 * Closing this input stream has no effect. The methods in this class can be called after the stream has been closed
030 * without generating an {@link IOException}.
031 * </p>
032 *
033 * @see InfiniteCircularInputStream
034 * @since 2.8.0
035 */
036public class CircularInputStream extends InputStream {
037
038    /**
039     * Throws an {@link IllegalArgumentException} if the input contains -1.
040     *
041     * @param repeatContent input to validate.
042     * @return the input.
043     */
044    private static byte[] validate(final byte[] repeatContent) {
045        Objects.requireNonNull(repeatContent, "repeatContent");
046        for (final byte b : repeatContent) {
047            if (b == IOUtils.EOF) {
048                throw new IllegalArgumentException("repeatContent contains the end-of-stream marker " + IOUtils.EOF);
049            }
050        }
051        return repeatContent;
052    }
053
054    private long byteCount;
055    private int position = -1;
056    private final byte[] repeatedContent;
057    private final long targetByteCount;
058
059    /**
060     * Creates an instance from the specified array of bytes.
061     *
062     * @param repeatContent Input buffer to be repeated this buffer is not copied.
063     * @param targetByteCount How many bytes the read. A negative number means an infinite target count.
064     */
065    public CircularInputStream(final byte[] repeatContent, final long targetByteCount) {
066        this.repeatedContent = validate(repeatContent);
067        if (repeatContent.length == 0) {
068            throw new IllegalArgumentException("repeatContent is empty.");
069        }
070        this.targetByteCount = targetByteCount;
071    }
072
073    @Override
074    public int read() {
075        if (targetByteCount >= 0) {
076            if (byteCount == targetByteCount) {
077                return IOUtils.EOF;
078            }
079            byteCount++;
080        }
081        position = (position + 1) % repeatedContent.length;
082        return repeatedContent[position] & 0xff;
083    }
084
085}