/*

 * 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 6499848

 * @ignore until 6842353 is resolved

 * @summary Check that iterators work properly in the presence of

 *          concurrent finalization and removal of elements.

 */

import java.util.*;

import java.util.concurrent.CountDownLatch;

public class GCDuringIteration {

    private static void waitForFinalizersToRun() {

        for (int i = 0; i < 2; i++)

            tryWaitForFinalizersToRun();

    }

    private static void tryWaitForFinalizersToRun() {

        System.gc();

        final CountDownLatch fin = new CountDownLatch(1);

        new Object() { protected void finalize() { fin.countDown(); }};

        System.gc();

        try { fin.await(); }

        catch (InterruptedException ie) { throw new Error(ie); }

    }

    // A class with the traditional pessimal hashCode implementation,

    // to ensure that all instances end up in the same bucket.

    static class Foo { public int hashCode() { return 42; }}

    <K,V> void put(Map<K,V> map, K k, V v) {

        check(! map.containsKey(k));

        equal(map.get(k), null);

        equal(map.put(k, v), null);

        equal(map.get(k), v);

        check(map.containsKey(k));

        equal(map.put(k, v), v);

        equal(map.get(k), v);

        check(map.containsKey(k));

        check(! map.isEmpty());

        equal(map.keySet().iterator().next(), k);

        equal(map.values().iterator().next(), v);

    }

    void checkIterator(final Iterator<Map.Entry<Foo, Integer>> it, int first) {

        final Random rnd = new Random();

        for (int i = first; i >= 0; --i) {

            if (rnd.nextBoolean()) check(it.hasNext());

            equal(it.next().getValue(), i);

        }

        if (rnd.nextBoolean())

            THROWS(NoSuchElementException.class,

                   new F(){void f(){it.next();}});

        if (rnd.nextBoolean())

            check(! it.hasNext());

    }

    <K,V> V firstValue(Map<K,V> map) {

        return map.values().iterator().next();

    }

    void test(String[] args) throws Throwable {

        final int n = 10;

        // Create array of strong refs

        final Foo[] foos = new Foo[2*n];

        final Map<Foo,Integer> map = new WeakHashMap<Foo,Integer>(foos.length);

        check(map.isEmpty());

        equal(map.size(), 0);

        for (int i = 0; i < foos.length; i++) {

            Foo foo = new Foo();

            foos[i] = foo;

            put(map, foo, i);

        }

        equal(map.size(), foos.length);

        {

            int first = firstValue(map);

            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();

            foos[first] = null;

            for (int i = 0; i < 10 && map.size() != first; i++)

                tryWaitForFinalizersToRun();

            equal(map.size(), first);

            checkIterator(it, first-1);

            equal(map.size(), first);

            equal(firstValue(map), first-1);

        }

        {

            int first = firstValue(map);

            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();

            it.next();          // protects first entry

            System.out.println(map.values());

            foos[first] = null;

            tryWaitForFinalizersToRun()

            equal(map.size(), first+1);

            System.out.println(map.values());

            checkIterator(it, first-1);

            // first entry no longer protected

            for (int i = 0; i < 10 && map.size() != first; i++)

                tryWaitForFinalizersToRun();

            equal(map.size(), first);

            equal(firstValue(map), first-1);

        }

        {

            int first = firstValue(map);

            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();

            it.next();          // protects first entry

            System.out.println(map.values());

            foos[first] = foos[first-1] = null;

            tryWaitForFinalizersToRun();

            equal(map.size(), first);

            equal(firstValue(map), first);

            System.out.println(map.values());

            checkIterator(it, first-2);

            // first entry no longer protected

            for (int i = 0; i < 10 && map.size() != first-1; i++)

                tryWaitForFinalizersToRun();

            equal(map.size(), first-1);

            equal(firstValue(map), first-2);

        }

        {

            int first = firstValue(map);

            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();

            it.next();          // protects first entry

            it.hasNext();       // protects second entry

            System.out.println(map.values());

            foos[first] = foos[first-1] = null;

            tryWaitForFinalizersToRun();

            equal(firstValue(map), first);

            equal(map.size(), first+1);

            System.out.println(map.values());

            checkIterator(it, first-1);

            // first entry no longer protected

            for (int i = 0; i < 10 && map.size() != first-1; i++)

                tryWaitForFinalizersToRun();

            equal(map.size(), first-1);

            equal(firstValue(map), first-2);

        }

        {

            int first = firstValue(map);

            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();

            it.next();          // protects first entry

            System.out.println(map.values());

            foos[first] = foos[first-1] = null;

            tryWaitForFinalizersToRun();

            it.remove();

            equal(firstValue(map), first-2);

            equal(map.size(), first-1);

            System.out.println(map.values());

            checkIterator(it, first-2);

            // first entry no longer protected

            for (int i = 0; i < 10 && map.size() != first-1; i++)

                tryWaitForFinalizersToRun();

            equal(map.size(), first-1);

            equal(firstValue(map), first-2);

        }

        {

            int first = firstValue(map);

            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();

            it.next();          // protects first entry

            it.remove();

            it.hasNext();       // protects second entry

            System.out.println(map.values());

            foos[first] = foos[first-1] = null;

            tryWaitForFinalizersToRun();

            equal(firstValue(map), first-1);

            equal(map.size(), first);

            System.out.println(map.values());

            checkIterator(it, first-1);

            for (int i = 0; i < 10 && map.size() != first-1; i++)

                tryWaitForFinalizersToRun();

            equal(map.size(), first-1);

            equal(firstValue(map), first-2);

        }

        {

            int first = firstValue(map);

            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();

            it.hasNext();       // protects first entry

            Arrays.fill(foos, null);

            tryWaitForFinalizersToRun();

            equal(map.size(), 1);

            System.out.println(map.values());

            equal(it.next().getValue(), first);

            check(! it.hasNext());

            for (int i = 0; i < 10 && map.size() != 0; i++)

                tryWaitForFinalizersToRun();

            equal(map.size(), 0);

            check(map.isEmpty());

        }

    }

    //--------------------- Infrastructure ---------------------------

    volatile int passed = 0, failed = 0;

    void pass() {passed++;}

    void fail() {failed++; Thread.dumpStack();}

    void fail(String msg) {System.err.println(msg); fail();}

    void unexpected(Throwable t) {failed++; t.printStackTrace();}

    void check(boolean cond) {if (cond) pass(); else fail();}

    void equal(Object x, Object y) {

        if (x == null ? y == null : x.equals(y)) pass();

        else fail(x + " not equal to " + y);}

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

        new GCDuringIteration().instanceMain(args);}

    void instanceMain(String[] args) throws Throwable {

        try {test(args);} catch (Throwable t) {unexpected(t);}

        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);

        if (failed > 0) throw new AssertionError("Some tests failed");}

    abstract class F {abstract void f() throws Throwable;}

    void THROWS(Class<? extends Throwable> k, F... fs) {

        for (F f : fs)

            try {f.f(); fail("Expected " + k.getName() + " not thrown");}

            catch (Throwable t) {

                if (k.isAssignableFrom(t.getClass())) pass();

                else unexpected(t);}}

}