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products/Sources/formale Sprachen/Java/Openjdk/test/jdk/java/io/StreamTokenizer/ (Sun/Oracle ^©) Datei vom 13.11.2022 mit Größe 4 kB

Quelle ReadAhead.java Sprache: JAVA

/*
* Copyright (c) 1999, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

/* @test
   @bug 4150737
   @summary Ensure that StreamTokenizer does not read any further ahead
            than is absolutely necessary
*/

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StreamTokenizer;
import java.io.IOException;

public class ReadAhead {

    /* An InputStream subclass that cannot read past a given limit */
    private static class LimitedInputStream extends InputStream {

        private String input;
        private int limit;      /* Do not allow input[limit] to be read */
        private int next = 0;

        public LimitedInputStream(String input, int limit) {
            this.input = input;
            this.limit = limit;
        }

        public int read() throws IOException {
            if (next >= limit)
                throw new IOException("Attempted to read too far in stream");
            return input.charAt(next++);
        }

    }

    /* A Reader subclass that cannot read past a given limit */
    private static class LimitedReader extends Reader {

        private String input;
        private int limit;      /* Do not allow input[limit] to be read */
        private int next = 0;

        public LimitedReader(String input, int limit) {
            this.input = input;
            this.limit = limit;
        }

        public int read() throws IOException {
            if (next >= limit)
                throw new IOException("Attempted to read too far in stream");
            return input.charAt(next++);
        }

        public int read(char[] b, int off, int len) throws IOException {
            int top = off + len;
            int i;
            for (i = off; i < top; i++) {
                int c = read();
                if (c < 0) break;
                b[i] = (char)c;
            }
            return i - off;
        }

        public void close() { }

    }

    /* Interface for objects that can create new StreamTokenizers
       with a given limited input */
    private static interface StreamTokenizerMaker {
        public StreamTokenizer create(String input, int limit);
    }

    private static void fail(String why) throws Exception {
        throw new Exception(why);
    }

    private static void test(StreamTokenizer st) throws Exception {
        st.eolIsSignificant(true);
        int tt = st.nextToken();
        if (tt != StreamTokenizer.TT_WORD) fail("expected TT_WORD");
        if (!st.sval.equals("foo")) fail("expected word token \"foo\"");
        tt = st.nextToken();
        if (tt != StreamTokenizer.TT_EOL) fail("expected TT_EOL");
    }

    private static void test(StreamTokenizerMaker stm) throws Exception {
        test(stm.create("foo\nx", 4));
        test(stm.create("foo\r\nx", 4));
    }

    public static void main(String[] args) throws Exception {

        /* InputStream case */
        test(new StreamTokenizerMaker() {
            public StreamTokenizer create(String input, int limit) {
                return new StreamTokenizer(new LimitedInputStream(input, limit));
            }});

        /* Reader case */
        test(new StreamTokenizerMaker() {
            public StreamTokenizer create(String input, int limit) {
                return new StreamTokenizer(new LimitedReader(input, limit));
            }});

    }

}

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