    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}