1 /*
2  * Copyright (c) 1999, Oracle and/or its affiliates. All rights reserved.
3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4  *
5  * This code is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 only, as
7  * published by the Free Software Foundation.
8  *
9  * This code is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12  * version 2 for more details (a copy is included in the LICENSE file that
13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
21  * questions.
22  */
23 
24 /* @test
25    @bug 4150737
26    @summary Ensure that StreamTokenizer does not read any further ahead
27             than is absolutely necessary
28  */
29 
30 import java.io.ByteArrayInputStream;
31 import java.io.InputStream;
32 import java.io.InputStreamReader;
33 import java.io.Reader;
34 import java.io.StreamTokenizer;
35 import java.io.IOException;
36 
37 
38 public class ReadAhead {
39 
40 
41     /* An InputStream subclass that cannot read past a given limit */
42     static private class LimitedInputStream extends InputStream {
43 
44         private String input;
45         private int limit;      /* Do not allow input[limit] to be read */
46         private int next = 0;
47 
LimitedInputStream(String input, int limit)48         public LimitedInputStream(String input, int limit) {
49             this.input = input;
50             this.limit = limit;
51         }
52 
read()53         public int read() throws IOException {
54             if (next >= limit)
55                 throw new IOException("Attempted to read too far in stream");
56             return input.charAt(next++);
57         }
58 
59     }
60 
61 
62     /* A Reader subclass that cannot read past a given limit */
63     static private class LimitedReader extends Reader {
64 
65         private String input;
66         private int limit;      /* Do not allow input[limit] to be read */
67         private int next = 0;
68 
LimitedReader(String input, int limit)69         public LimitedReader(String input, int limit) {
70             this.input = input;
71             this.limit = limit;
72         }
73 
read()74         public int read() throws IOException {
75             if (next >= limit)
76                 throw new IOException("Attempted to read too far in stream");
77             return input.charAt(next++);
78         }
79 
read(char[] b, int off, int len)80         public int read(char[] b, int off, int len) throws IOException {
81             int top = off + len;
82             int i;
83             for (i = off; i < top; i++) {
84                 int c = read();
85                 if (c < 0) break;
86                 b[i] = (char)c;
87             }
88             return i - off;
89         }
90 
close()91         public void close() { }
92 
93     }
94 
95 
96     /* Interface for objects that can create new StreamTokenizers
97        with a given limited input */
98     static private interface StreamTokenizerMaker {
create(String input, int limit)99         public StreamTokenizer create(String input, int limit);
100     }
101 
fail(String why)102     static private void fail(String why) throws Exception {
103         throw new Exception(why);
104     }
105 
test(StreamTokenizer st)106     private static void test(StreamTokenizer st) throws Exception {
107         st.eolIsSignificant(true);
108         int tt = st.nextToken();
109         if (tt != StreamTokenizer.TT_WORD) fail("expected TT_WORD");
110         if (!st.sval.equals("foo")) fail("expected word token \"foo\"");
111         tt = st.nextToken();
112         if (tt != StreamTokenizer.TT_EOL) fail("expected TT_EOL");
113     }
114 
test(StreamTokenizerMaker stm)115     private static void test(StreamTokenizerMaker stm) throws Exception {
116         test(stm.create("foo\nx", 4));
117         test(stm.create("foo\r\nx", 4));
118     }
119 
120 
main(String[] args)121     public static void main(String[] args) throws Exception {
122 
123         /* InputStream case */
124         test(new StreamTokenizerMaker() {
125             public StreamTokenizer create(String input, int limit) {
126                 return new StreamTokenizer(new LimitedInputStream(input, limit));
127             }});
128 
129         /* Reader case */
130         test(new StreamTokenizerMaker() {
131             public StreamTokenizer create(String input, int limit) {
132                 return new StreamTokenizer(new LimitedReader(input, limit));
133             }});
134 
135     }
136 
137 }
138