Coverage Summary for Class: MultiReader (com.google.common.io)

1 /*
2  * Copyright (C) 2008 The Guava Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5  * in compliance with the License. You may obtain a copy of the License at
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software distributed under the License
10  * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11  * or implied. See the License for the specific language governing permissions and limitations under
12  * the License.
13  */
14 
15 package com.google.common.io;
16 
17 import static com.google.common.base.Preconditions.checkNotNull;
18 
19 import com.google.common.annotations.GwtIncompatible;
20 import com.google.common.base.Preconditions;
21 import java.io.IOException;
22 import java.io.Reader;
23 import java.util.Iterator;
24 import javax.annotation.CheckForNull;
25 
26 /**
27  * A {@link Reader} that concatenates multiple readers.
28  *
29  * @author Bin Zhu
30  * @since 1.0
31  */
32 @GwtIncompatible
33 @ElementTypesAreNonnullByDefault
34 class MultiReader extends Reader {
35   private final Iterator<? extends CharSource> it;
36   @CheckForNull private Reader current;
37 
38   MultiReader(Iterator<? extends CharSource> readers) throws IOException {
39     this.it = readers;
40     advance();
41   }
42 
43   /** Closes the current reader and opens the next one, if any. */
44   private void advance() throws IOException {
45     close();
46     if (it.hasNext()) {
47       current = it.next().openStream();
48     }
49   }
50 
51   @Override
52   public int read(char[] cbuf, int off, int len) throws IOException {
53     checkNotNull(cbuf);
54     if (current == null) {
55       return -1;
56     }
57     int result = current.read(cbuf, off, len);
58     if (result == -1) {
59       advance();
60       return read(cbuf, off, len);
61     }
62     return result;
63   }
64 
65   @Override
66   public long skip(long n) throws IOException {
67     Preconditions.checkArgument(n >= 0, "n is negative");
68     if (n > 0) {
69       while (current != null) {
70         long result = current.skip(n);
71         if (result > 0) {
72           return result;
73         }
74         advance();
75       }
76     }
77     return 0;
78   }
79 
80   @Override
81   public boolean ready() throws IOException {
82     return (current != null) && current.ready();
83   }
84 
85   @Override
86   public void close() throws IOException {
87     if (current != null) {
88       try {
89         current.close();
90       } finally {
91         current = null;
92       }
93     }
94   }
95 }