1/*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.io;
18
19import static com.google.common.base.Preconditions.checkNotNull;
20
21import java.io.IOException;
22import java.io.InputStream;
23import java.util.Iterator;
24
25import javax.annotation.Nullable;
26
27/**
28 * An {@link InputStream} that concatenates multiple substreams. At most
29 * one stream will be open at a time.
30 *
31 * @author Chris Nokleberg
32 * @since 1.0
33 */
34final class MultiInputStream extends InputStream {
35
36  private Iterator<? extends ByteSource> it;
37  private InputStream in;
38
39  /**
40   * Creates a new instance.
41   *
42   * @param it an iterator of I/O suppliers that will provide each substream
43   */
44  public MultiInputStream(
45      Iterator<? extends ByteSource> it) throws IOException {
46    this.it = checkNotNull(it);
47    advance();
48  }
49
50  @Override public void close() throws IOException {
51    if (in != null) {
52      try {
53        in.close();
54      } finally {
55        in = null;
56      }
57    }
58  }
59
60  /**
61   * Closes the current input stream and opens the next one, if any.
62   */
63  private void advance() throws IOException {
64    close();
65    if (it.hasNext()) {
66      in = it.next().openStream();
67    }
68  }
69
70  @Override public int available() throws IOException {
71    if (in == null) {
72      return 0;
73    }
74    return in.available();
75  }
76
77  @Override public boolean markSupported() {
78    return false;
79  }
80
81  @Override public int read() throws IOException {
82    if (in == null) {
83      return -1;
84    }
85    int result = in.read();
86    if (result == -1) {
87      advance();
88      return read();
89    }
90    return result;
91  }
92
93  @Override public int read(@Nullable byte[] b, int off, int len) throws IOException {
94    if (in == null) {
95      return -1;
96    }
97    int result = in.read(b, off, len);
98    if (result == -1) {
99      advance();
100      return read(b, off, len);
101    }
102    return result;
103  }
104
105  @Override public long skip(long n) throws IOException {
106    if (in == null || n <= 0) {
107      return 0;
108    }
109    long result = in.skip(n);
110    if (result != 0) {
111      return result;
112    }
113    if (read() == -1) {
114      return 0;
115    }
116    return 1 + in.skip(n - 1);
117  }
118}
119