1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.io.input;
18
19 import java.io.IOException;
20 import java.io.InputStream;
21 import java.util.Objects;
22
23 import org.apache.commons.io.IOUtils;
24
25 /**
26 * An {@link InputStream} that repeats provided bytes for given target byte count.
27 * <p>
28 * Closing this input stream has no effect. The methods in this class can be called after the stream has been closed
29 * without generating an {@link IOException}.
30 * </p>
31 *
32 * @see InfiniteCircularInputStream
33 * @since 2.8.0
34 */
35 public class CircularInputStream extends InputStream {
36
37 /**
38 * Throws an {@link IllegalArgumentException} if the input contains -1.
39 *
40 * @param repeatContent input to validate.
41 * @return the input.
42 */
43 private static byte[] validate(final byte[] repeatContent) {
44 Objects.requireNonNull(repeatContent, "repeatContent");
45 for (final byte b : repeatContent) {
46 if (b == IOUtils.EOF) {
47 throw new IllegalArgumentException("repeatContent contains the end-of-stream marker " + IOUtils.EOF);
48 }
49 }
50 return repeatContent;
51 }
52
53 private long byteCount;
54 private int position = IOUtils.EOF;
55 private final byte[] repeatedContent;
56 private final long targetByteCount;
57
58 /**
59 * Constructs an instance from the specified array of bytes.
60 *
61 * @param repeatContent Input buffer to be repeated this buffer is not copied.
62 * @param targetByteCount How many bytes the read. A negative number means an infinite target count.
63 */
64 public CircularInputStream(final byte[] repeatContent, final long targetByteCount) {
65 this.repeatedContent = validate(repeatContent);
66 if (repeatContent.length == 0) {
67 throw new IllegalArgumentException("repeatContent is empty.");
68 }
69 this.targetByteCount = targetByteCount;
70 }
71
72 @Override
73 public int read() {
74 if (targetByteCount >= 0) {
75 if (byteCount == targetByteCount) {
76 return IOUtils.EOF;
77 }
78 byteCount++;
79 }
80 position = (position + 1) % repeatedContent.length;
81 return repeatedContent[position] & 0xff;
82 }
83
84 }