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 static org.apache.commons.io.IOUtils.EOF;
20
21 import java.io.IOException;
22 import java.io.Reader;
23 import java.io.SequenceInputStream;
24 import java.util.Arrays;
25 import java.util.Iterator;
26 import java.util.Objects;
27
28 import org.apache.commons.io.function.Uncheck;
29
30 /**
31 * Provides the contents of multiple {@link Reader}s in sequence.
32 * <p>
33 * Like {@link SequenceInputStream} but for {@link Reader} arguments.
34 * </p>
35 *
36 * @since 2.7
37 */
38 public class SequenceReader extends Reader {
39
40 private Reader reader;
41 private final Iterator<? extends Reader> readers;
42
43 /**
44 * Constructs a new instance with readers
45 *
46 * @param readers the readers to read
47 */
48 public SequenceReader(final Iterable<? extends Reader> readers) {
49 this.readers = Objects.requireNonNull(readers, "readers").iterator();
50 this.reader = Uncheck.get(this::nextReader);
51 }
52
53 /**
54 * Constructs a new instance with readers
55 *
56 * @param readers the readers to read
57 */
58 public SequenceReader(final Reader... readers) {
59 this(Arrays.asList(readers));
60 }
61
62 /*
63 * (non-Javadoc)
64 *
65 * @see java.io.Reader#close()
66 */
67 @Override
68 public void close() throws IOException {
69 do { // NOPMD
70 // empty
71 } while (nextReader() != null);
72 }
73
74 /**
75 * Returns the next available reader or null if done.
76 *
77 * @return the next available reader or null.
78 * @throws IOException IOException If an I/O error occurs.
79 */
80 private Reader nextReader() throws IOException {
81 if (reader != null) {
82 reader.close();
83 }
84 if (readers.hasNext()) {
85 reader = readers.next();
86 } else {
87 reader = null;
88 }
89 return reader;
90 }
91
92 /*
93 * (non-Javadoc)
94 *
95 * @see java.io.Reader#read(char[], int, int)
96 */
97 @Override
98 public int read() throws IOException {
99 int c = EOF;
100 while (reader != null) {
101 c = reader.read();
102 if (c != EOF) {
103 break;
104 }
105 nextReader();
106 }
107 return c;
108 }
109
110 /*
111 * (non-Javadoc)
112 *
113 * @see java.io.Reader#read()
114 */
115 @Override
116 public int read(final char[] cbuf, int off, int len) throws IOException {
117 Objects.requireNonNull(cbuf, "cbuf");
118 if (len < 0 || off < 0 || off + len > cbuf.length) {
119 throw new IndexOutOfBoundsException("Array Size=" + cbuf.length + ", offset=" + off + ", length=" + len);
120 }
121 int count = 0;
122 while (reader != null) {
123 final int readLen = reader.read(cbuf, off, len);
124 if (readLen == EOF) {
125 nextReader();
126 } else {
127 count += readLen;
128 off += readLen;
129 len -= readLen;
130 if (len <= 0) {
131 break;
132 }
133 }
134 }
135 if (count > 0) {
136 return count;
137 }
138 return EOF;
139 }
140 }