Quellcode-Bibliothek

^© Kompilation durch diese Firma

[Weder Korrektheit noch Funktionsfähigkeit der Software werden zugesichert.]

Datei: Skip.java Sprache: JAVA

/*
* Copyright (c) 1997, 2018, 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 4016710 6516099
* @summary check for correct implementation of InputStream.skip{NBytes}
*/

import java.io.EOFException;
import java.io.InputStream;
import java.io.IOException;

public class Skip {
    private static final int EOF = -1;

    private static void dotest(InputStream in, int curpos, long total,
                               long toskip, long expected) throws Exception {
        try {
            System.err.println("\n\nCurrently at pos = " + curpos +
                               "\nTotal bytes in the Stream = " + total +
                               "\nNumber of bytes to skip = " + toskip +
                               "\nNumber of bytes that should be skipped = " +
                               expected);

            long skipped = in.skip(toskip);

            System.err.println("actual number skipped: "+ skipped);

            if ((skipped < 0) || (skipped > expected)) {
                throw new RuntimeException("Unexpected byte count skipped");
            }
        } catch (IOException e) {
            System.err.println("IOException is thrown: " + e);
        } catch (Throwable e) {
            throw new RuntimeException("Unexpected " + e + " is thrown!");
        }
    }

    private static void dotestExact(MyInputStream in, long curpos, long total,
        long toskip, boolean expectIOE, boolean expectEOFE) {

        System.err.println("\n\nCurrently at pos = " + curpos +
                           "\nTotal bytes in the Stream = " + total +
                           "\nNumber of bytes to skip = " + toskip);

        try {
            long pos = in.position();
            assert pos == curpos : pos + " != " + curpos;
            in.skipNBytes(toskip);
            if (in.position() != pos + (toskip < 0 ? 0 : toskip)) {
                throw new RuntimeException((in.position() - pos) +
                    " bytes skipped; expected " + toskip);
            }
        } catch (EOFException eofe) {
            if (!expectEOFE) {
                throw new RuntimeException("Unexpected EOFException", eofe);
            }
            System.err.println("Caught expected EOFException");
        } catch (IOException ioe) {
            if (!expectIOE) {
                throw new RuntimeException("Unexpected IOException", ioe);
            }
            System.err.println("Caught expected IOException");
        }
    }

    public static void main( String argv[] ) throws Exception {
        MyInputStream in = new MyInputStream(11);

        // test for negative skip
        dotest(in,  0, 11, -23,  0);

        // check for skip beyond EOF starting from before EOF
        dotest(in,  0, 11,  20, 11);

        // check for skip after EOF
        dotest(in, EOF, 11,  20,  0);

        in = new MyInputStream(9000);

        // check for skip equal to the read chunk size in InputStream.java
        dotest(in,  0, 9000, 2048, 2048);

        // check for skip larger than the read chunk size in InputStream.java
        dotest(in, 2048, 9000, 5000, 5000);

        // check for skip beyond EOF starting from before EOF
        dotest(in, 7048, 9000, 5000, 1952);

        in = new MyInputStream(5000);

        // check for multiple chunk reads
        dotest(in, 0, 5000, 6000, 5000);

        /*
         * check for skip larger than Integer.MAX_VALUE
         * (Takes about 2 hrs on a sparc ultra-1)
         * long total = (long)Integer.MAX_VALUE + (long)10;
         * long toskip = total - (long)6;
         * in = new MyInputStream(total);
         * dotest(in, 0, total, toskip, toskip);
         */

        // tests for skipping an exact number of bytes

        final long streamLength = Long.MAX_VALUE;
        in = new MyInputStream(streamLength);

        // negative skip: OK
        dotestExact(in, 0, streamLength, -1, false, false);

        // negative skip at EOF: OK
        in.position(streamLength);
        dotestExact(in, streamLength, streamLength, -1, false, false);
        in.position(0);

        // zero skip: OK
        dotestExact(in, 0, streamLength, 0, false, false);

        // zero skip at EOF: OK
        in.position(streamLength);
        dotestExact(in, streamLength, streamLength, 0, false, false);

        // skip(1) at EOF: EOFE
        dotestExact(in, streamLength, streamLength, 1, false, true);
        in.position(0);

        final long n = 31; // skip count
        long pos = 0;

        // skip(n) returns negative value: IOE
        in.setState(-1, 100);
        dotestExact(in, pos, streamLength, n, true, false);

        // skip(n) returns n + 1: IOE
        in.setState(n + 1, 100);
        dotestExact(in, pos, streamLength, n, true, false);
        pos += n + 1;

        // skip(n) returns n/2 but only n/4 subsequent reads succeed: EOFE
        in.setState(n/2, n/2 + n/4);
        dotestExact(in, pos, streamLength, n, false, true);
        pos += n/2 + n/4;

        // skip(n) returns n/2 but n - n/2 subsequent reads succeed: OK
        in.setState(n/2, n);
        dotestExact(in, pos, streamLength, n, false, false);
        pos += n;
    }
}

class MyInputStream extends InputStream {
    private static final int EOF = -1;

    private final long endoffile;

    private long readctr = 0;

    private boolean isStateSet = false;
    private long skipReturn;
    private long readLimit;

    public MyInputStream(long endoffile) {
        this.endoffile = endoffile;
    }

    /**
     * Limits the behavior of skip() and read().
     *
     * @param skipReturn the value to be returned by skip()
     * @param maxReads   the maximum number of reads past the current position
     *                   before EOF is reached
     */
    public void setState(long skipReturn, long maxReads) {
        this.skipReturn = skipReturn;
        this.readLimit = readctr + maxReads;
        isStateSet = true;
    }

    public int read() {
        if (readctr == endoffile ||
            (isStateSet && readctr >= readLimit)) {
            return EOF;
        }
        else {
            readctr++;
            return 0;
        }
    }

    public int available() { return 0; }

    public long position() { return readctr; }

    public void position(long pos) {
        readctr = pos < 0 ? 0 : Math.min(pos, endoffile);
    }

    public long skip(long n) throws IOException {
        if (isStateSet) {
            return skipReturn < 0 ? skipReturn : super.skip(skipReturn);
        }

        // InputStream skip implementation.
        return super.skip(n); // readctr is implicitly incremented
    }
}

¤ Dauer der Verarbeitung: 0.1 Sekunden (vorverarbeitet) ¤

Download des Quellennavigators
Download des sprechenden Kalenders
in der Quellcodebibliothek suchen

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.