/*
 * 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, int curpos, long total,
                                    long toskip) throws Exception {
        try {
            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 (!(toskip > 0 &&
                    (curpos == EOF || (curpos + toskip > total)))) {
                    throw new RuntimeException("Unexpected EOFException", eofe);
                }

                System.err.println("Caught expected EOFException");

                return;
            }
        } catch (IOException e) {
            System.err.println("IOException is thrown: " + e);
        } catch (Throwable e) {
            throw new RuntimeException("Unexpected " + e + " is thrown!");
        }
    }

    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 */

        in = new MyInputStream(11);

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

        /* test for zero skip */
        dotestExact(in,  0, 11, 0);

        /* test for skip before EOF */
        dotestExact(in,  0, 11, 5);

        /* check for skip beyond EOF starting from before EOF */
        dotestExact(in,  5, 11, 7);

        /* check for skip from / after EOF */
        dotestExact(in, EOF, 11, 1);
    }
}

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

    private long readctr = 0;
    private long endoffile;

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

    public int read() {
        if (readctr == endoffile) {
            return EOF;
        }
        else {
            readctr++;
            return 0;
        }
    }

    public int available() { return 0; }

    public long position() { return readctr == endoffile ? EOF : readctr; }
}