package com.ajjpj.afoundation.concurrent;

import com.ajjpj.afoundation.collection.immutable.AList;
import com.ajjpj.afoundation.collection.immutable.AOption;
import com.ajjpj.afoundation.collection.immutable.ATry;
import com.ajjpj.afoundation.function.AFunction0;
import com.ajjpj.afoundation.function.AFunction1;
import com.ajjpj.afoundation.function.AFunction2;
import com.ajjpj.afoundation.function.APredicate;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

class StaticFutureMethods {
    public static <T, E extends Throwable> AFuture<T> submit (AThreadPool tp, AFunction0<T, E> f) {
        final AFutureImpl<T> result = new AFutureImpl<> (tp);
        tp.submit (() -> {
            try {
                result.completeAsSuccess (f.apply ());
            }
            catch (Throwable th) {
                result.completeAsFailure (th);
                //TODO distinguish between safe and unsafe throwables
            }
        });
        return result;
    }

    public static <T> AFuture<AList<T>> lift (AThreadPool tp, Iterable<AFuture<T>> futures) {
        final AFutureImpl<AList<T>> result = new AFutureImpl<> (tp);

        int numFutures = 0;
        for (AFuture<T> ignored: futures) numFutures += 1;
        final AtomicInteger numUnbound = new AtomicInteger (numFutures);

        final List<T> list = new ArrayList<> ();
        for (AFuture<T> f: futures) {
            int idx = list.size();
            list.add (null);

            f.onComplete (AThreadPool.SYNC_THREADPOOL, tr -> {
                if (tr.isSuccess ()) {
                    list.set (idx, tr.getValue ());
                    if (numUnbound.decrementAndGet () == 0) {
                        result.tryComplete (ATry.success (AList.create (list)));
                    }
                }
                else {
                    //noinspection unchecked
                    result.tryComplete ((ATry<AList<T>>) tr);
                }
            });
        }

        if (list.isEmpty ()) {
            result.completeAsSuccess (AList.nil ());
        }

        return result;
    }

    public static <T> AFuture<T> firstCompleted (AThreadPool tp, Iterable<AFuture<T>> futures) {
        final AFutureImpl<T> result = new AFutureImpl<> (tp);

        for (AFuture<T> f: futures) {
            f.onComplete (AThreadPool.SYNC_THREADPOOL, result::tryComplete);
        }

        return result;
    }

    public static <T> AFuture<AOption<T>> find (AThreadPool tp, Iterable<AFuture<T>> futures, APredicate<T, ?> f) {
        int numFutures = 0;
        for (AFuture<T> ignored: futures) numFutures += 1;
        final AtomicInteger numOpen = new AtomicInteger (numFutures);

        if (numFutures == 0) {
            return AFuture.createSuccessful (AOption.none ());
        }

        final AFutureImpl<AOption<T>> result = new AFutureImpl<> (tp);

        for (AFuture<T> future: futures) {
            future.onComplete (tp, tr -> {
                if (tr.isSuccess () && f.apply (tr.getValue ())) {
                    result.tryComplete (tr.map (AOption::some));
                }
                else {
                    if (numOpen.decrementAndGet () == 0) {
                        result.tryComplete (ATry.success (AOption.none ()));
                    }
                }
            });
        }

        return result;
    }

    public static <R, T, E extends Throwable> AFuture<R> fold (AThreadPool tp, R start, Iterable<AFuture<T>> futures, AFunction2<R, T, R, E> f) {
        if (! futures.iterator ().hasNext ()) return AFuture.createSuccessful (start);

        final AFuture<AList<T>> lifted = StaticFutureMethods.lift (tp, futures);
        return lifted.map (tp, x -> x.foldLeft (start, f));
    }

    //TODO AMonadicOps.reduceLeft
//    public static <T, E extends Throwable> AFuture<T> reduce (AThreadPool tp, Iterable<AFuture<T>> futures, AFunction2<T, T, T, E> f) {
//        final AFuture<List<T>> lifted = StaticFutureMethods.lift (tp, futures);
//        return lifted.map (tp, x -> ACollectionHelper.asACollectionView (x).<R,E>reduceLeft (f));
//    }

    public static <R, T, E extends Throwable> AFuture<AList<R>> traverse (AThreadPool tp, Iterable<T> values, AFunction1<T, AFuture<R>, E> f) throws E {
        final List<AFuture<R>> result = new ArrayList<> ();
        for (T o: values) {
            result.add (f.apply (o));
        }
        return lift (tp, result);
    }
}


package com.ajjpj.afoundation.concurrent;

import com.ajjpj.afoundation.util.AUnchecker;
import sun.misc.Contended;
import sun.misc.Unsafe;

import java.lang.reflect.Field;

/**
 * @author arno
 */
@Contended
class SharedQueueNonBlockingImpl implements ASharedQueue {
    long p1, p2, p3, p4, p5, p6, p7;

    private final int prefetchBatchSize;
    /**
     * an array holding all currently submitted tasks.
     */
    private final Runnable[] tasks;

    /**
     * a bit mask to project an offset into the valid range of offsets for the tasks array
     */
    private final int mask;

    private final AThreadPoolImpl pool;

    private long base = 0;
    private long top = 0;

    long q1, q2, q3, q4, q5, q6, q7;

    SharedQueueNonBlockingImpl (int prefetchBatchSize, AThreadPoolImpl pool, int size) {
        if (prefetchBatchSize < 1) throw new IllegalArgumentException ("worker threads must (attempt to) fetch a minimum of 1 task");
        this.prefetchBatchSize = prefetchBatchSize;
        this.pool = pool;

        if (1 != Integer.bitCount (size)) throw new IllegalArgumentException ("size must be a power of 2");
        if (size < 8 || size > 1024*1024) throw new IllegalArgumentException ("size must be in the range from 8 to " + (1024*1024));

        this.tasks = new Runnable[size];
        this.mask = size-1;
    }

    /**
     * @return an approximation of the queue's current size. The value may be stale and is not synchronized in any way, and it is intended for debugging and statistics
     *  purposes only.
     */
    @Override public int approximateSize () {
        return (int) (
                UNSAFE.getLongVolatile (this, OFFS_TOP) -
                UNSAFE.getLongVolatile (this, OFFS_BASE)
        );
    }

    /**
     * Add a new task to the top of the shared queue, incrementing 'top'.
     */
    @Override public void push (Runnable task) {
        while (true) {
            final long _base = UNSAFE.getLongVolatile (this, OFFS_BASE);
            final long _top = top;

            if (_top == _base + mask) {
                throw new RejectedExecutionExceptionWithoutStacktrace ("Queue overflow");
            }

            final long taskOffset = taskOffset (_top);
            if (UNSAFE.compareAndSwapObject (tasks, taskOffset, null, task)) {
                // if the publishing thread is interrupted here, other publishers will effectively do a spin wait
                if (!UNSAFE.compareAndSwapLong (this, OFFS_TOP, _top, _top+1)) {
                    // there was a buffer wrap-around in the meantime --> undo the CAS 'put' operation and try again
                    UNSAFE.putObjectVolatile (tasks, taskOffset, null);
                    continue;
                }

                if (_top - _base <= 1) {
                    pool.onAvailableTask ();
                }
                break;
            }
        }
    }

    @Override public synchronized Runnable popFifo (LocalQueue localQueue) {
        final long _base = base;
        final long _top = top;

        final long size = _top-_base;

        if (size == 0) {
            // Terminate the loop: the queue is empty.
            //TODO verify that Hotspot optimizes this kind of return-from-the-middle well
            return null;
        }

        final Runnable result = fetchTask (_base);
        if (result == null) {
            System.err.println ("null @ " + _base);
            return null; //TODO why is this necessary?
        }

        int idx;

        long newLocalTop = localQueue.top;
        for (idx=1; idx < size && idx < prefetchBatchSize; idx++) {
            final Runnable task = fetchTask (_base+idx);
            if (task == null) {
                System.err.println ("************************ fetched task[base+" + idx + "] is null although it really couldn't *******************************");
            }

            localQueue.tasks [localQueue.asArrayindex (newLocalTop++)] = task;
        }

        // volatile put for atomicity and to ensure ordering wrt. nulling the task --> read operations do not hold the same monitor
        if (idx > 1) {
            UNSAFE.putLongVolatile (localQueue, LocalQueue.OFFS_TOP, newLocalTop);
        }

        // volatile put for atomicity and to ensure ordering wrt. nulling the task --> read operations do not hold the same monitor
        UNSAFE.putLongVolatile (this, OFFS_BASE, _base + idx);

        return result;
    }

    private Runnable fetchTask (long idx) {
        final int arrIdx = asArrayIndex (idx);
        final Runnable result = tasks [arrIdx];
        if (result != null) tasks[arrIdx] = null; //TODO remove the check
        return result;
    }

    @Override public synchronized void clear () {
        final long _top = top;
        for (long _base=base; _base < _top; _base++) {
            tasks[asArrayIndex (_base)] = null;
        }

        UNSAFE.putLongVolatile (this, OFFS_BASE, _top);
    }

    private long taskOffset (long l) {
        return OFFS_TASKS + SCALE_TASKS * (l & mask);
    }

    private int asArrayIndex (long l) {
        return (int) (l & mask);
    }

    //------------- Unsafe stuff
    private static final Unsafe UNSAFE;

    private static final long OFFS_TASKS;
    private static final long SCALE_TASKS;

    private static final long OFFS_BASE;
    private static final long OFFS_TOP;

    static {
        try {
            final Field f = Unsafe.class.getDeclaredField ("theUnsafe");
            f.setAccessible (true);
            UNSAFE = (Unsafe) f.get (null);

            OFFS_TASKS = UNSAFE.arrayBaseOffset (Runnable[].class);
            SCALE_TASKS = UNSAFE.arrayIndexScale (Runnable[].class);

            OFFS_BASE = UNSAFE.objectFieldOffset (SharedQueueNonBlockingImpl.class.getDeclaredField ("base"));
            OFFS_TOP  = UNSAFE.objectFieldOffset (SharedQueueNonBlockingImpl.class.getDeclaredField ("top"));
        }
        catch (Exception e) {
            AUnchecker.throwUnchecked (e);
            throw new RuntimeException(); // for the compiler
        }
    }
}


/*
 * 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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.
 */

/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package com.ajjpj.afoundation.concurrent.jdk.j9new;

import sun.misc.Unsafe;

import java.io.Serializable;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.util.Collection;
import java.util.List;
import java.util.RandomAccess;
import java.util.concurrent.*;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Abstract base class for tasks that run within a {@link ForkJoinPool}.
 * A {@code ForkJoinTask} is a thread-like entity that is much
 * lighter weight than a normal thread.  Huge numbers of tasks and
 * subtasks may be hosted by a small number of actual threads in a
 * ForkJoinPool, at the price of some usage limitations.
 *
 *
A "main" {@code ForkJoinTask} begins execution when it is
 * explicitly submitted to a {@link ForkJoinPool}, or, if not already
 * engaged in a ForkJoin computation, commenced in the {@link
 * ForkJoinPool#commonPool()} via {@link #fork}, {@link #invoke}, or
 * related methods.  Once started, it will usually in turn start other
 * subtasks.  As indicated by the name of this class, many programs
 * using {@code ForkJoinTask} employ only methods {@link #fork} and
 * {@link #join}, or derivatives such as {@link
 * #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
 * provides a number of other methods that can come into play in
 * advanced usages, as well as extension mechanics that allow support
 * of new forms of fork/join processing.
 *
 *
A {@code ForkJoinTask} is a lightweight form of {@link Future}.
 * The efficiency of {@code ForkJoinTask}s stems from a set of
 * restrictions (that are only partially statically enforceable)
 * reflecting their main use as computational tasks calculating pure
 * functions or operating on purely isolated objects.  The primary
 * coordination mechanisms are {@link #fork}, that arranges
 * asynchronous execution, and {@link #join}, that doesn't proceed
 * until the task's result has been computed.  Computations should
 * ideally avoid {@code synchronized} methods or blocks, and should
 * minimize other blocking synchronization apart from joining other
 * tasks or using synchronizers such as Phasers that are advertised to
 * cooperate with fork/join scheduling. Subdividable tasks should also
 * not perform blocking I/O, and should ideally access variables that
 * are completely independent of those accessed by other running
 * tasks. These guidelines are loosely enforced by not permitting
 * checked exceptions such as {@code IOExceptions} to be
 * thrown. However, computations may still encounter unchecked
 * exceptions, that are rethrown to callers attempting to join
 * them. These exceptions may additionally include {@link
 * RejectedExecutionException} stemming from internal resource
 * exhaustion, such as failure to allocate internal task
 * queues. Rethrown exceptions behave in the same way as regular
 * exceptions, but, when possible, contain stack traces (as displayed
 * for example using {@code ex.printStackTrace()}) of both the thread
 * that initiated the computation as well as the thread actually
 * encountering the exception; minimally only the latter.
 *
 *
It is possible to define and use ForkJoinTasks that may block,
 * but doing do requires three further considerations: (1) Completion
 * of few if any other tasks should be dependent on a task
 * that blocks on external synchronization or I/O. Event-style async
 * tasks that are never joined (for example, those subclassing {@link
 * CountedCompleter}) often fall into this category.  (2) To minimize
 * resource impact, tasks should be small; ideally performing only the
 * (possibly) blocking action. (3) Unless the {@link
 * ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
 * blocked tasks is known to be less than the pool's {@link
 * ForkJoinPool#getParallelism} level, the pool cannot guarantee that
 * enough threads will be available to ensure progress or good
 * performance.
 *
 *
The primary method for awaiting completion and extracting
 * results of a task is {@link #join}, but there are several variants:
 * The {@link Future#get} methods support interruptible and/or timed
 * waits for completion and report results using {@code Future}
 * conventions. Method {@link #invoke} is semantically
 * equivalent to {@code fork(); join()} but always attempts to begin
 * execution in the current thread. The "quiet" forms of
 * these methods do not extract results or report exceptions. These
 * may be useful when a set of tasks are being executed, and you need
 * to delay processing of results or exceptions until all complete.
 * Method {@code invokeAll} (available in multiple versions)
 * performs the most common form of parallel invocation: forking a set
 * of tasks and joining them all.
 *
 *
In the most typical usages, a fork-join pair act like a call
 * (fork) and return (join) from a parallel recursive function. As is
 * the case with other forms of recursive calls, returns (joins)
 * should be performed innermost-first. For example, {@code a.fork();
 * b.fork(); b.join(); a.join();} is likely to be substantially more
 * efficient than joining {@code a} before {@code b}.
 *
 *
The execution status of tasks may be queried at several levels
 * of detail: {@link #isDone} is true if a task completed in any way
 * (including the case where a task was cancelled without executing);
 * {@link #isCompletedNormally} is true if a task completed without
 * cancellation or encountering an exception; {@link #isCancelled} is
 * true if the task was cancelled (in which case {@link #getException}
 * returns a {@link CancellationException}); and
 * {@link #isCompletedAbnormally} is true if a task was either
 * cancelled or encountered an exception, in which case {@link
 * #getException} will return either the encountered exception or
 * {@link CancellationException}.
 *
 *
The ForkJoinTask class is not usually directly subclassed.
 * Instead, you subclass one of the abstract classes that support a
 * particular style of fork/join processing, typically {@link
 * RecursiveAction} for most computations that do not return results,
 * {@link RecursiveTask} for those that do, and {@link
 * CountedCompleter} for those in which completed actions trigger
 * other actions.  Normally, a concrete ForkJoinTask subclass declares
 * fields comprising its parameters, established in a constructor, and
 * then defines a {@code compute} method that somehow uses the control
 * methods supplied by this base class.
 *
 *
Method {@link #join} and its variants are appropriate for use
 * only when completion dependencies are acyclic; that is, the
 * parallel computation can be described as a directed acyclic graph
 * (DAG). Otherwise, executions may encounter a form of deadlock as
 * tasks cyclically wait for each other.  However, this framework
 * supports other methods and techniques (for example the use of
 * {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
 * may be of use in constructing custom subclasses for problems that
 * are not statically structured as DAGs. To support such usages, a
 * ForkJoinTask may be atomically tagged with a {@code short}
 * value using {@link #setForkJoinTaskTag} or {@link
 * #compareAndSetForkJoinTaskTag} and checked using {@link
 * #getForkJoinTaskTag}. The ForkJoinTask implementation does not use
 * these {@code protected} methods or tags for any purpose, but they
 * may be of use in the construction of specialized subclasses.  For
 * example, parallel graph traversals can use the supplied methods to
 * avoid revisiting nodes/tasks that have already been processed.
 * (Method names for tagging are bulky in part to encourage definition
 * of methods that reflect their usage patterns.)
 *
 *
Most base support methods are {@code final}, to prevent
 * overriding of implementations that are intrinsically tied to the
 * underlying lightweight task scheduling framework.  Developers
 * creating new basic styles of fork/join processing should minimally
 * implement {@code protected} methods {@link #exec}, {@link
 * #setRawResult}, and {@link #getRawResult}, while also introducing
 * an abstract computational method that can be implemented in its
 * subclasses, possibly relying on other {@code protected} methods
 * provided by this class.
 *
 *
ForkJoinTasks should perform relatively small amounts of
 * computation. Large tasks should be split into smaller subtasks,
 * usually via recursive decomposition. As a very rough rule of thumb,
 * a task should perform more than 100 and less than 10000 basic
 * computational steps, and should avoid indefinite looping. If tasks
 * are too big, then parallelism cannot improve throughput. If too
 * small, then memory and internal task maintenance overhead may
 * overwhelm processing.
 *
 *
This class provides {@code adapt} methods for {@link Runnable}
 * and {@link Callable}, that may be of use when mixing execution of
 * {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
 * of this form, consider using a pool constructed in asyncMode.
 *
 *
ForkJoinTasks are {@code Serializable}, which enables them to be
 * used in extensions such as remote execution frameworks. It is
 * sensible to serialize tasks only before or after, but not during,
 * execution. Serialization is not relied on during execution itself.
 *
 * @since 1.7
 * @author Doug Lea
 */
public abstract class ForkJoinTask<V> implements Future<V>, Serializable {

    /*
     * See the internal documentation of class ForkJoinPool for a
     * general implementation overview.  ForkJoinTasks are mainly
     * responsible for maintaining their "status" field amidst relays
     * to methods in ForkJoinWorkerThread and ForkJoinPool.
     *
     * The methods of this class are more-or-less layered into
     * (1) basic status maintenance
     * (2) execution and awaiting completion
     * (3) user-level methods that additionally report results.
     * This is sometimes hard to see because this file orders exported
     * methods in a way that flows well in javadocs.
     */

    /*
     * The status field holds run control status bits packed into a
     * single int to minimize footprint and to ensure atomicity (via
     * CAS).  Status is initially zero, and takes on nonnegative
     * values until completed, upon which status (anded with
     * DONE_MASK) holds value NORMAL, CANCELLED, or EXCEPTIONAL. Tasks
     * undergoing blocking waits by other threads have the SIGNAL bit
     * set.  Completion of a stolen task with SIGNAL set awakens any
     * waiters via notifyAll. Even though suboptimal for some
     * purposes, we use basic builtin wait/notify to take advantage of
     * "monitor inflation" in JVMs that we would otherwise need to
     * emulate to avoid adding further per-task bookkeeping overhead.
     * We want these monitors to be "fat", i.e., not use biasing or
     * thin-lock techniques, so use some odd coding idioms that tend
     * to avoid them, mainly by arranging that every synchronized
     * block performs a wait, notifyAll or both.
     *
     * These control bits occupy only (some of) the upper half (16
     * bits) of status field. The lower bits are used for user-defined
     * tags.
     */

    /** The run status of this task */
    volatile int status; // accessed directly by pool and workers
    static final int DONE_MASK   = 0xf0000000;  // mask out non-completion bits
    static final int NORMAL      = 0xf0000000;  // must be negative
    static final int CANCELLED   = 0xc0000000;  // must be < NORMAL
    static final int EXCEPTIONAL = 0x80000000;  // must be < CANCELLED
    static final int SIGNAL      = 0x00010000;  // must be >= 1 << 16
    static final int SMASK       = 0x0000ffff;  // short bits for tags

    /**
     * Marks completion and wakes up threads waiting to join this
     * task.
     *
     * @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
     * @return completion status on exit
     */
    private int setCompletion(int completion) {
        for (int s;;) {
            if ((s = status) < 0)
                return s;
            if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
                if ((s >>> 16) != 0)
                    synchronized (this) { notifyAll(); }
                return completion;
            }
        }
    }

    /**
     * Primary execution method for stolen tasks. Unless done, calls
     * exec and records status if completed, but doesn't wait for
     * completion otherwise.
     *
     * @return status on exit from this method
     */
    final int doExec() {
        int s; boolean completed;
        if ((s = status) >= 0) {
            try {
                completed = exec();
            } catch (Throwable rex) {
                return setExceptionalCompletion(rex);
            }
            if (completed)
                s = setCompletion(NORMAL);
        }
        return s;
    }

    /**
     * If not done, sets SIGNAL status and performs Object.wait(timeout).
     * This task may or may not be done on exit. Ignores interrupts.
     *
     * @param timeout using Object.wait conventions.
     */
    final void internalWait(long timeout) {
        int s;
        if ((s = status) >= 0 && // force completer to issue notify
            U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
            synchronized (this) {
                if (status >= 0)
                    try { wait(timeout); } catch (InterruptedException ie) { }
                else
                    notifyAll();
            }
        }
    }

    /**
     * Blocks a non-worker-thread until completion.
     * @return status upon completion
     */
    private int externalAwaitDone() {
        int s = ((this instanceof CountedCompleter) ? // try helping
                 ForkJoinPool.common.externalHelpComplete(
                     (CountedCompleter<?>)this, 0) :
                 ForkJoinPool.common.tryExternalUnpush(this) ? doExec() : 0);
        if (s >= 0 && (s = status) >= 0) {
            boolean interrupted = false;
            do {
                if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
                    synchronized (this) {
                        if (status >= 0) {
                            try {
                                wait(0L);
                            } catch (InterruptedException ie) {
                                interrupted = true;
                            }
                        }
                        else
                            notifyAll();
                    }
                }
            } while ((s = status) >= 0);
            if (interrupted)
                Thread.currentThread().interrupt();
        }
        return s;
    }

    /**
     * Blocks a non-worker-thread until completion or interruption.
     */
    private int externalInterruptibleAwaitDone() throws InterruptedException {
        int s;
        if (Thread.interrupted())
            throw new InterruptedException();
        if ((s = status) >= 0 &&
            (s = ((this instanceof CountedCompleter) ?
                  ForkJoinPool.common.externalHelpComplete(
                      (CountedCompleter<?>)this, 0) :
                  ForkJoinPool.common.tryExternalUnpush(this) ? doExec() :
                  0)) >= 0) {
            while ((s = status) >= 0) {
                if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
                    synchronized (this) {
                        if (status >= 0)
                            wait(0L);
                        else
                            notifyAll();
                    }
                }
            }
        }
        return s;
    }

    /**
     * Implementation for join, get, quietlyJoin. Directly handles
     * only cases of already-completed, external wait, and
     * unfork+exec.  Others are relayed to ForkJoinPool.awaitJoin.
     *
     * @return status upon completion
     */
    private int doJoin() {
        int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
        return (s = status) < 0 ? s :
            ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
            (w = (wt = (ForkJoinWorkerThread)t).workQueue).
            tryUnpush(this) && (s = doExec()) < 0 ? s :
            wt.pool.awaitJoin(w, this, 0L) :
            externalAwaitDone();
    }

    /**
     * Implementation for invoke, quietlyInvoke.
     *
     * @return status upon completion
     */
    private int doInvoke() {
        int s; Thread t; ForkJoinWorkerThread wt;
        return (s = doExec()) < 0 ? s :
            ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
            (wt = (ForkJoinWorkerThread)t).pool.
            awaitJoin(wt.workQueue, this, 0L) :
            externalAwaitDone();
    }

    // Exception table support

    /**
     * Table of exceptions thrown by tasks, to enable reporting by
     * callers. Because exceptions are rare, we don't directly keep
     * them with task objects, but instead use a weak ref table.  Note
     * that cancellation exceptions don't appear in the table, but are
     * instead recorded as status values.
     *
     * Note: These statics are initialized below in static block.
     */
    private static final ExceptionNode[] exceptionTable;
    private static final ReentrantLock exceptionTableLock;
    private static final ReferenceQueue<Object> exceptionTableRefQueue;

    /**
     * Fixed capacity for exceptionTable.
     */
    private static final int EXCEPTION_MAP_CAPACITY = 32;

    /**
     * Key-value nodes for exception table.  The chained hash table
     * uses identity comparisons, full locking, and weak references
     * for keys. The table has a fixed capacity because it only
     * maintains task exceptions long enough for joiners to access
     * them, so should never become very large for sustained
     * periods. However, since we do not know when the last joiner
     * completes, we must use weak references and expunge them. We do
     * so on each operation (hence full locking). Also, some thread in
     * any ForkJoinPool will call helpExpungeStaleExceptions when its
     * pool becomes isQuiescent.
     */
    static final class ExceptionNode extends WeakReference<ForkJoinTask<?>> {
        final Throwable ex;
        ExceptionNode next;
        final long thrower;  // use id not ref to avoid weak cycles
        final int hashCode;  // store task hashCode before weak ref disappears
        ExceptionNode(ForkJoinTask<?> task, Throwable ex, ExceptionNode next) {
            super(task, exceptionTableRefQueue);
            this.ex = ex;
            this.next = next;
            this.thrower = Thread.currentThread().getId();
            this.hashCode = System.identityHashCode(task);
        }
    }

    /**
     * Records exception and sets status.
     *
     * @return status on exit
     */
    final int recordExceptionalCompletion(Throwable ex) {
        int s;
        if ((s = status) >= 0) {
            int h = System.identityHashCode(this);
            final ReentrantLock lock = exceptionTableLock;
            lock.lock();
            try {
                expungeStaleExceptions();
                ExceptionNode[] t = exceptionTable;
                int i = h & (t.length - 1);
                for (ExceptionNode e = t[i]; ; e = e.next) {
                    if (e == null) {
                        t[i] = new ExceptionNode(this, ex, t[i]);
                        break;
                    }
                    if (e.get() == this) // already present
                        break;
                }
            } finally {
                lock.unlock();
            }
            s = setCompletion(EXCEPTIONAL);
        }
        return s;
    }

    /**
     * Records exception and possibly propagates.
     *
     * @return status on exit
     */
    private int setExceptionalCompletion(Throwable ex) {
        int s = recordExceptionalCompletion(ex);
        if ((s & DONE_MASK) == EXCEPTIONAL)
            internalPropagateException(ex);
        return s;
    }

    /**
     * Hook for exception propagation support for tasks with completers.
     */
    void internalPropagateException(Throwable ex) {
    }

    /**
     * Cancels, ignoring any exceptions thrown by cancel. Used during
     * worker and pool shutdown. Cancel is spec'ed not to throw any
     * exceptions, but if it does anyway, we have no recourse during
     * shutdown, so guard against this case.
     */
    static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
        if (t != null && t.status >= 0) {
            try {
                t.cancel(false);
            } catch (Throwable ignore) {
            }
        }
    }

    /**
     * Removes exception node and clears status.
     */
    private void clearExceptionalCompletion() {
        int h = System.identityHashCode(this);
        final ReentrantLock lock = exceptionTableLock;
        lock.lock();
        try {
            ExceptionNode[] t = exceptionTable;
            int i = h & (t.length - 1);
            ExceptionNode e = t[i];
            ExceptionNode pred = null;
            while (e != null) {
                ExceptionNode next = e.next;
                if (e.get() == this) {
                    if (pred == null)
                        t[i] = next;
                    else
                        pred.next = next;
                    break;
                }
                pred = e;
                e = next;
            }
            expungeStaleExceptions();
            status = 0;
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns a rethrowable exception for the given task, if
     * available. To provide accurate stack traces, if the exception
     * was not thrown by the current thread, we try to create a new
     * exception of the same type as the one thrown, but with the
     * recorded exception as its cause. If there is no such
     * constructor, we instead try to use a no-arg constructor,
     * followed by initCause, to the same effect. If none of these
     * apply, or any fail due to other exceptions, we return the
     * recorded exception, which is still correct, although it may
     * contain a misleading stack trace.
     *
     * @return the exception, or null if none
     */
    private Throwable getThrowableException() {
        if ((status & DONE_MASK) != EXCEPTIONAL)
            return null;
        int h = System.identityHashCode(this);
        ExceptionNode e;
        final ReentrantLock lock = exceptionTableLock;
        lock.lock();
        try {
            expungeStaleExceptions();
            ExceptionNode[] t = exceptionTable;
            e = t[h & (t.length - 1)];
            while (e != null && e.get() != this)
                e = e.next;
        } finally {
            lock.unlock();
        }
        Throwable ex;
        if (e == null || (ex = e.ex) == null)
            return null;
        if (e.thrower != Thread.currentThread().getId()) {
            Class<? extends Throwable> ec = ex.getClass();
            try {
                Constructor<?> noArgCtor = null;
                Constructor<?>[] cs = ec.getConstructors();// public ctors only
                for (int i = 0; i < cs.length; ++i) {
                    Constructor<?> c = cs[i];
                    Class<?>[] ps = c.getParameterTypes();
                    if (ps.length == 0)
                        noArgCtor = c;
                    else if (ps.length == 1 && ps[0] == Throwable.class) {
                        Throwable wx = (Throwable)c.newInstance(ex);
                        return (wx == null) ? ex : wx;
                    }
                }
                if (noArgCtor != null) {
                    Throwable wx = (Throwable)(noArgCtor.newInstance());
                    if (wx != null) {
                        wx.initCause(ex);
                        return wx;
                    }
                }
            } catch (Exception ignore) {
            }
        }
        return ex;
    }

    /**
     * Poll stale refs and remove them. Call only while holding lock.
     */
    private static void expungeStaleExceptions() {
        for (Object x; (x = exceptionTableRefQueue.poll()) != null;) {
            if (x instanceof ExceptionNode) {
                int hashCode = ((ExceptionNode)x).hashCode;
                ExceptionNode[] t = exceptionTable;
                int i = hashCode & (t.length - 1);
                ExceptionNode e = t[i];
                ExceptionNode pred = null;
                while (e != null) {
                    ExceptionNode next = e.next;
                    if (e == x) {
                        if (pred == null)
                            t[i] = next;
                        else
                            pred.next = next;
                        break;
                    }
                    pred = e;
                    e = next;
                }
            }
        }
    }

    /**
     * If lock is available, poll stale refs and remove them.
     * Called from ForkJoinPool when pools become quiescent.
     */
    static final void helpExpungeStaleExceptions() {
        final ReentrantLock lock = exceptionTableLock;
        if (lock.tryLock()) {
            try {
                expungeStaleExceptions();
            } finally {
                lock.unlock();
            }
        }
    }

    /**
     * A version of "sneaky throw" to relay exceptions
     */
    static void rethrow(Throwable ex) {
        if (ex != null)
            ForkJoinTask.<RuntimeException>uncheckedThrow(ex);
    }

    /**
     * The sneaky part of sneaky throw, relying on generics
     * limitations to evade compiler complaints about rethrowing
     * unchecked exceptions
     */
    @SuppressWarnings("unchecked") static <T extends Throwable>
        void uncheckedThrow(Throwable t) throws T {
        throw (T)t; // rely on vacuous cast
    }

    /**
     * Throws exception, if any, associated with the given status.
     */
    private void reportException(int s) {
        if (s == CANCELLED)
            throw new CancellationException();
        if (s == EXCEPTIONAL)
            rethrow(getThrowableException());
    }

    // public methods

    /**
     * Arranges to asynchronously execute this task in the pool the
     * current task is running in, if applicable, or using the {@link
     * ForkJoinPool#commonPool()} if not {@link #inForkJoinPool}.  While
     * it is not necessarily enforced, it is a usage error to fork a
     * task more than once unless it has completed and been
     * reinitialized.  Subsequent modifications to the state of this
     * task or any data it operates on are not necessarily
     * consistently observable by any thread other than the one
     * executing it unless preceded by a call to {@link #join} or
     * related methods, or a call to {@link #isDone} returning {@code
     * true}.
     *
     * @return {@code this}, to simplify usage
     */
    public final ForkJoinTask<V> fork() {
        Thread t;
        if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
            ((ForkJoinWorkerThread)t).workQueue.push(this);
        else
            ForkJoinPool.common.externalPush(this);
        return this;
    }

    /**
     * Returns the result of the computation when it {@link #isDone is
     * done}.  This method differs from {@link #get()} in that
     * abnormal completion results in {@code RuntimeException} or
     * {@code Error}, not {@code ExecutionException}, and that
     * interrupts of the calling thread do not cause the
     * method to abruptly return by throwing {@code
     * InterruptedException}.
     *
     * @return the computed result
     */
    public final V join() {
        int s;
        if ((s = doJoin() & DONE_MASK) != NORMAL)
            reportException(s);
        return getRawResult();
    }

    /**
     * Commences performing this task, awaits its completion if
     * necessary, and returns its result, or throws an (unchecked)
     * {@code RuntimeException} or {@code Error} if the underlying
     * computation did so.
     *
     * @return the computed result
     */
    public final V invoke() {
        int s;
        if ((s = doInvoke() & DONE_MASK) != NORMAL)
            reportException(s);
        return getRawResult();
    }

    /**
     * Forks the given tasks, returning when {@code isDone} holds for
     * each task or an (unchecked) exception is encountered, in which
     * case the exception is rethrown. If more than one task
     * encounters an exception, then this method throws any one of
     * these exceptions. If any task encounters an exception, the
     * other may be cancelled. However, the execution status of
     * individual tasks is not guaranteed upon exceptional return. The
     * status of each task may be obtained using {@link
     * #getException()} and related methods to check if they have been
     * cancelled, completed normally or exceptionally, or left
     * unprocessed.
     *
     * @param t1 the first task
     * @param t2 the second task
     * @throws NullPointerException if any task is null
     */
    public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
        int s1, s2;
        t2.fork();
        if ((s1 = t1.doInvoke() & DONE_MASK) != NORMAL)
            t1.reportException(s1);
        if ((s2 = t2.doJoin() & DONE_MASK) != NORMAL)
            t2.reportException(s2);
    }

    /**
     * Forks the given tasks, returning when {@code isDone} holds for
     * each task or an (unchecked) exception is encountered, in which
     * case the exception is rethrown. If more than one task
     * encounters an exception, then this method throws any one of
     * these exceptions. If any task encounters an exception, others
     * may be cancelled. However, the execution status of individual
     * tasks is not guaranteed upon exceptional return. The status of
     * each task may be obtained using {@link #getException()} and
     * related methods to check if they have been cancelled, completed
     * normally or exceptionally, or left unprocessed.
     *
     * @param tasks the tasks
     * @throws NullPointerException if any task is null
     */
    public static void invokeAll(ForkJoinTask<?>... tasks) {
        Throwable ex = null;
        int last = tasks.length - 1;
        for (int i = last; i >= 0; --i) {
            ForkJoinTask<?> t = tasks[i];
            if (t == null) {
                if (ex == null)
                    ex = new NullPointerException();
            }
            else if (i != 0)
                t.fork();
            else if (t.doInvoke() < NORMAL && ex == null)
                ex = t.getException();
        }
        for (int i = 1; i <= last; ++i) {
            ForkJoinTask<?> t = tasks[i];
            if (t != null) {
                if (ex != null)
                    t.cancel(false);
                else if (t.doJoin() < NORMAL)
                    ex = t.getException();
            }
        }
        if (ex != null)
            rethrow(ex);
    }

    /**
     * Forks all tasks in the specified collection, returning when
     * {@code isDone} holds for each task or an (unchecked) exception
     * is encountered, in which case the exception is rethrown. If
     * more than one task encounters an exception, then this method
     * throws any one of these exceptions. If any task encounters an
     * exception, others may be cancelled. However, the execution
     * status of individual tasks is not guaranteed upon exceptional
     * return. The status of each task may be obtained using {@link
     * #getException()} and related methods to check if they have been
     * cancelled, completed normally or exceptionally, or left
     * unprocessed.
     *
     * @param tasks the collection of tasks
     * @param <T> the type of the values returned from the tasks
     * @return the tasks argument, to simplify usage
     * @throws NullPointerException if tasks or any element are null
     */
    public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
        if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
            invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
            return tasks;
        }
        @SuppressWarnings("unchecked")
        List<? extends ForkJoinTask<?>> ts =
            (List<? extends ForkJoinTask<?>>) tasks;
        Throwable ex = null;
        int last = ts.size() - 1;
        for (int i = last; i >= 0; --i) {
            ForkJoinTask<?> t = ts.get(i);
            if (t == null) {
                if (ex == null)
                    ex = new NullPointerException();
            }
            else if (i != 0)
                t.fork();
            else if (t.doInvoke() < NORMAL && ex == null)
                ex = t.getException();
        }
        for (int i = 1; i <= last; ++i) {
            ForkJoinTask<?> t = ts.get(i);
            if (t != null) {
                if (ex != null)
                    t.cancel(false);
                else if (t.doJoin() < NORMAL)
                    ex = t.getException();
            }
        }
        if (ex != null)
            rethrow(ex);
        return tasks;
    }

    /**
     * Attempts to cancel execution of this task. This attempt will
     * fail if the task has already completed or could not be
     * cancelled for some other reason. If successful, and this task
     * has not started when {@code cancel} is called, execution of
     * this task is suppressed. After this method returns
     * successfully, unless there is an intervening call to {@link
     * #reinitialize}, subsequent calls to {@link #isCancelled},
     * {@link #isDone}, and {@code cancel} will return {@code true}
     * and calls to {@link #join} and related methods will result in
     * {@code CancellationException}.
     *
     *
This method may be overridden in subclasses, but if so, must
     * still ensure that these properties hold. In particular, the
     * {@code cancel} method itself must not throw exceptions.
     *
     *
This method is designed to be invoked by other
     * tasks. To terminate the current task, you can just return or
     * throw an unchecked exception from its computation method, or
     * invoke {@link #completeExceptionally(Throwable)}.
     *
     * @param mayInterruptIfRunning this value has no effect in the
     * default implementation because interrupts are not used to
     * control cancellation.
     *
     * @return {@code true} if this task is now cancelled
     */
    public boolean cancel(boolean mayInterruptIfRunning) {
        return (setCompletion(CANCELLED) & DONE_MASK) == CANCELLED;
    }

    public final boolean isDone() {
        return status < 0;
    }

    public final boolean isCancelled() {
        return (status & DONE_MASK) == CANCELLED;
    }

    /**
     * Returns {@code true} if this task threw an exception or was cancelled.
     *
     * @return {@code true} if this task threw an exception or was cancelled
     */
    public final boolean isCompletedAbnormally() {
        return status < NORMAL;
    }

    /**
     * Returns {@code true} if this task completed without throwing an
     * exception and was not cancelled.
     *
     * @return {@code true} if this task completed without throwing an
     * exception and was not cancelled
     */
    public final boolean isCompletedNormally() {
        return (status & DONE_MASK) == NORMAL;
    }

    /**
     * Returns the exception thrown by the base computation, or a
     * {@code CancellationException} if cancelled, or {@code null} if
     * none or if the method has not yet completed.
     *
     * @return the exception, or {@code null} if none
     */
    public final Throwable getException() {
        int s = status & DONE_MASK;
        return ((s >= NORMAL)    ? null :
                (s == CANCELLED) ? new CancellationException() :
                getThrowableException());
    }

    /**
     * Completes this task abnormally, and if not already aborted or
     * cancelled, causes it to throw the given exception upon
     * {@code join} and related operations. This method may be used
     * to induce exceptions in asynchronous tasks, or to force
     * completion of tasks that would not otherwise complete.  Its use
     * in other situations is discouraged.  This method is
     * overridable, but overridden versions must invoke {@code super}
     * implementation to maintain guarantees.
     *
     * @param ex the exception to throw. If this exception is not a
     * {@code RuntimeException} or {@code Error}, the actual exception
     * thrown will be a {@code RuntimeException} with cause {@code ex}.
     */
    public void completeExceptionally(Throwable ex) {
        setExceptionalCompletion((ex instanceof RuntimeException) ||
                                 (ex instanceof Error) ? ex :
                                 new RuntimeException(ex));
    }

    /**
     * Completes this task, and if not already aborted or cancelled,
     * returning the given value as the result of subsequent
     * invocations of {@code join} and related operations. This method
     * may be used to provide results for asynchronous tasks, or to
     * provide alternative handling for tasks that would not otherwise
     * complete normally. Its use in other situations is
     * discouraged. This method is overridable, but overridden
     * versions must invoke {@code super} implementation to maintain
     * guarantees.
     *
     * @param value the result value for this task
     */
    public void complete(V value) {
        try {
            setRawResult(value);
        } catch (Throwable rex) {
            setExceptionalCompletion(rex);
            return;
        }
        setCompletion(NORMAL);
    }

    /**
     * Completes this task normally without setting a value. The most
     * recent value established by {@link #setRawResult} (or {@code
     * null} by default) will be returned as the result of subsequent
     * invocations of {@code join} and related operations.
     *
     * @since 1.8
     */
    public final void quietlyComplete() {
        setCompletion(NORMAL);
    }

    /**
     * Waits if necessary for the computation to complete, and then
     * retrieves its result.
     *
     * @return the computed result
     * @throws CancellationException if the computation was cancelled
     * @throws ExecutionException if the computation threw an
     * exception
     * @throws InterruptedException if the current thread is not a
     * member of a ForkJoinPool and was interrupted while waiting
     */
    public final V get() throws InterruptedException, ExecutionException {
        int s = (Thread.currentThread() instanceof ForkJoinWorkerThread) ?
            doJoin() : externalInterruptibleAwaitDone();
        Throwable ex;
        if ((s &= DONE_MASK) == CANCELLED)
            throw new CancellationException();
        if (s == EXCEPTIONAL && (ex = getThrowableException()) != null)
            throw new ExecutionException(ex);
        return getRawResult();
    }

    /**
     * Waits if necessary for at most the given time for the computation
     * to complete, and then retrieves its result, if available.
     *
     * @param timeout the maximum time to wait
     * @param unit the time unit of the timeout argument
     * @return the computed result
     * @throws CancellationException if the computation was cancelled
     * @throws ExecutionException if the computation threw an
     * exception
     * @throws InterruptedException if the current thread is not a
     * member of a ForkJoinPool and was interrupted while waiting
     * @throws TimeoutException if the wait timed out
     */
    public final V get(long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException {
        int s;
        long nanos = unit.toNanos(timeout);
        if (Thread.interrupted())
            throw new InterruptedException();
        if ((s = status) >= 0 && nanos > 0L) {
            long d = System.nanoTime() + nanos;
            long deadline = (d == 0L) ? 1L : d; // avoid 0
            Thread t = Thread.currentThread();
            if (t instanceof ForkJoinWorkerThread) {
                ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
                s = wt.pool.awaitJoin(wt.workQueue, this, deadline);
            }
            else if ((s = ((this instanceof CountedCompleter) ?
                           ForkJoinPool.common.externalHelpComplete(
                               (CountedCompleter<?>)this, 0) :
                           ForkJoinPool.common.tryExternalUnpush(this) ?
                           doExec() : 0)) >= 0) {
                long ns, ms; // measure in nanosecs, but wait in millisecs
                while ((s = status) >= 0 &&
                       (ns = deadline - System.nanoTime()) > 0L) {
                    if ((ms = TimeUnit.NANOSECONDS.toMillis(ns)) > 0L &&
                        U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
                        synchronized (this) {
                            if (status >= 0)
                                wait(ms); // OK to throw InterruptedException
                            else
                                notifyAll();
                        }
                    }
                }
            }
        }
        if (s >= 0)
            s = status;
        if ((s &= DONE_MASK) != NORMAL) {
            Throwable ex;
            if (s == CANCELLED)
                throw new CancellationException();
            if (s != EXCEPTIONAL)
                throw new TimeoutException();
            if ((ex = getThrowableException()) != null)
                throw new ExecutionException(ex);
        }
        return getRawResult();
    }

    /**
     * Joins this task, without returning its result or throwing its
     * exception. This method may be useful when processing
     * collections of tasks when some have been cancelled or otherwise
     * known to have aborted.
     */
    public final void quietlyJoin() {
        doJoin();
    }

    /**
     * Commences performing this task and awaits its completion if
     * necessary, without returning its result or throwing its
     * exception.
     */
    public final void quietlyInvoke() {
        doInvoke();
    }

    /**
     * Possibly executes tasks until the pool hosting the current task
     * {@link ForkJoinPool#isQuiescent is quiescent}. This method may
     * be of use in designs in which many tasks are forked, but none
     * are explicitly joined, instead executing them until all are
     * processed.
     */
    public static void helpQuiesce() {
        Thread t;
        if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
            ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
            wt.pool.helpQuiescePool(wt.workQueue);
        }
        else
            ForkJoinPool.quiesceCommonPool();
    }

    /**
     * Resets the internal bookkeeping state of this task, allowing a
     * subsequent {@code fork}. This method allows repeated reuse of
     * this task, but only if reuse occurs when this task has either
     * never been forked, or has been forked, then completed and all
     * outstanding joins of this task have also completed. Effects
     * under any other usage conditions are not guaranteed.
     * This method may be useful when executing
     * pre-constructed trees of subtasks in loops.
     *
     *
Upon completion of this method, {@code isDone()} reports
     * {@code false}, and {@code getException()} reports {@code
     * null}. However, the value returned by {@code getRawResult} is
     * unaffected. To clear this value, you can invoke {@code
     * setRawResult(null)}.
     */
    public void reinitialize() {
        if ((status & DONE_MASK) == EXCEPTIONAL)
            clearExceptionalCompletion();
        else
            status = 0;
    }

    /**
     * Returns the pool hosting the current task execution, or null
     * if this task is executing outside of any ForkJoinPool.
     *
     * @see #inForkJoinPool
     * @return the pool, or {@code null} if none
     */
    public static ForkJoinPool getPool() {
        Thread t = Thread.currentThread();
        return (t instanceof ForkJoinWorkerThread) ?
            ((ForkJoinWorkerThread) t).pool : null;
    }

    /**
     * Returns {@code true} if the current thread is a {@link
     * ForkJoinWorkerThread} executing as a ForkJoinPool computation.
     *
     * @return {@code true} if the current thread is a {@link
     * ForkJoinWorkerThread} executing as a ForkJoinPool computation,
     * or {@code false} otherwise
     */
    public static boolean inForkJoinPool() {
        return Thread.currentThread() instanceof ForkJoinWorkerThread;
    }

    /**
     * Tries to unschedule this task for execution. This method will
     * typically (but is not guaranteed to) succeed if this task is
     * the most recently forked task by the current thread, and has
     * not commenced executing in another thread.  This method may be
     * useful when arranging alternative local processing of tasks
     * that could have been, but were not, stolen.
     *
     * @return {@code true} if unforked
     */
    public boolean tryUnfork() {
        Thread t;
        return (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
                ((ForkJoinWorkerThread)t).workQueue.tryUnpush(this) :
                ForkJoinPool.common.tryExternalUnpush(this));
    }

    /**
     * Returns an estimate of the number of tasks that have been
     * forked by the current worker thread but not yet executed. This
     * value may be useful for heuristic decisions about whether to
     * fork other tasks.
     *
     * @return the number of tasks
     */
    public static int getQueuedTaskCount() {
        Thread t; ForkJoinPool.WorkQueue q;
        if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
            q = ((ForkJoinWorkerThread)t).workQueue;
        else
            q = ForkJoinPool.commonSubmitterQueue();
        return (q == null) ? 0 : q.queueSize();
    }

    /**
     * Returns an estimate of how many more locally queued tasks are
     * held by the current worker thread than there are other worker
     * threads that might steal them, or zero if this thread is not
     * operating in a ForkJoinPool. This value may be useful for
     * heuristic decisions about whether to fork other tasks. In many
     * usages of ForkJoinTasks, at steady state, each worker should
     * aim to maintain a small constant surplus (for example, 3) of
     * tasks, and to process computations locally if this threshold is
     * exceeded.
     *
     * @return the surplus number of tasks, which may be negative
     */
    public static int getSurplusQueuedTaskCount() {
        return ForkJoinPool.getSurplusQueuedTaskCount();
    }

    // Extension methods

    /**
     * Returns the result that would be returned by {@link #join}, even
     * if this task completed abnormally, or {@code null} if this task
     * is not known to have been completed.  This method is designed
     * to aid debugging, as well as to support extensions. Its use in
     * any other context is discouraged.
     *
     * @return the result, or {@code null} if not completed
     */
    public abstract V getRawResult();

    /**
     * Forces the given value to be returned as a result.  This method
     * is designed to support extensions, and should not in general be
     * called otherwise.
     *
     * @param value the value
     */
    protected abstract void setRawResult(V value);

    /**
     * Immediately performs the base action of this task and returns
     * true if, upon return from this method, this task is guaranteed
     * to have completed normally. This method may return false
     * otherwise, to indicate that this task is not necessarily
     * complete (or is not known to be complete), for example in
     * asynchronous actions that require explicit invocations of
     * completion methods. This method may also throw an (unchecked)
     * exception to indicate abnormal exit. This method is designed to
     * support extensions, and should not in general be called
     * otherwise.
     *
     * @return {@code true} if this task is known to have completed normally
     */
    protected abstract boolean exec();

    /**
     * Returns, but does not unschedule or execute, a task queued by
     * the current thread but not yet executed, if one is immediately
     * available. There is no guarantee that this task will actually
     * be polled or executed next. Conversely, this method may return
     * null even if a task exists but cannot be accessed without
     * contention with other threads.  This method is designed
     * primarily to support extensions, and is unlikely to be useful
     * otherwise.
     *
     * @return the next task, or {@code null} if none are available
     */
    protected static ForkJoinTask<?> peekNextLocalTask() {
        Thread t; ForkJoinPool.WorkQueue q;
        if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
            q = ((ForkJoinWorkerThread)t).workQueue;
        else
            q = ForkJoinPool.commonSubmitterQueue();
        return (q == null) ? null : q.peek();
    }

    /**
     * Unschedules and returns, without executing, the next task
     * queued by the current thread but not yet executed, if the
     * current thread is operating in a ForkJoinPool.  This method is
     * designed primarily to support extensions, and is unlikely to be
     * useful otherwise.
     *
     * @return the next task, or {@code null} if none are available
     */
    protected static ForkJoinTask<?> pollNextLocalTask() {
        Thread t;
        return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
            ((ForkJoinWorkerThread)t).workQueue.nextLocalTask() :
            null;
    }

    /**
     * If the current thread is operating in a ForkJoinPool,
     * unschedules and returns, without executing, the next task
     * queued by the current thread but not yet executed, if one is
     * available, or if not available, a task that was forked by some
     * other thread, if available. Availability may be transient, so a
     * {@code null} result does not necessarily imply quiescence of
     * the pool this task is operating in.  This method is designed
     * primarily to support extensions, and is unlikely to be useful
     * otherwise.
     *
     * @return a task, or {@code null} if none are available
     */
    protected static ForkJoinTask<?> pollTask() {
        Thread t; ForkJoinWorkerThread wt;
        return ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
            (wt = (ForkJoinWorkerThread)t).pool.nextTaskFor(wt.workQueue) :
            null;
    }

    // tag operations

    /**
     * Returns the tag for this task.
     *
     * @return the tag for this task
     * @since 1.8
     */
    public final short getForkJoinTaskTag() {
        return (short)status;
    }

    /**
     * Atomically sets the tag value for this task.
     *
     * @param tag the tag value
     * @return the previous value of the tag
     * @since 1.8
     */
    public final short setForkJoinTaskTag(short tag) {
        for (int s;;) {
            if (U.compareAndSwapInt(this, STATUS, s = status,
                                    (s & ~SMASK) | (tag & SMASK)))
                return (short)s;
        }
    }

    /**
     * Atomically conditionally sets the tag value for this task.
     * Among other applications, tags can be used as visit markers
     * in tasks operating on graphs, as in methods that check: {@code
     * if (task.compareAndSetForkJoinTaskTag((short)0, (short)1))}
     * before processing, otherwise exiting because the node has
     * already been visited.
     *
     * @param e the expected tag value
     * @param tag the new tag value
     * @return {@code true} if successful; i.e., the current value was
     * equal to e and is now tag.
     * @since 1.8
     */
    public final boolean compareAndSetForkJoinTaskTag(short e, short tag) {
        for (int s;;) {
            if ((short)(s = status) != e)
                return false;
            if (U.compareAndSwapInt(this, STATUS, s,
                                    (s & ~SMASK) | (tag & SMASK)))
                return true;
        }
    }

    /**
     * Adaptor for Runnables. This implements RunnableFuture
     * to be compliant with AbstractExecutorService constraints
     * when used in ForkJoinPool.
     */
    static final class AdaptedRunnable<T> extends ForkJoinTask<T>
        implements RunnableFuture<T> {
        final Runnable runnable;
        T result;
        AdaptedRunnable(Runnable runnable, T result) {
            if (runnable == null) throw new NullPointerException();
            this.runnable = runnable;
            this.result = result; // OK to set this even before completion
        }
        public final T getRawResult() { return result; }
        public final void setRawResult(T v) { result = v; }
        public final boolean exec() { runnable.run(); return true; }
        public final void run() { invoke(); }
        private static final long serialVersionUID = 5232453952276885070L;
    }

    /**
     * Adaptor for Runnables without results
     */
    static final class AdaptedRunnableAction extends ForkJoinTask<Void>
        implements RunnableFuture<Void> {
        final Runnable runnable;
        AdaptedRunnableAction(Runnable runnable) {
            if (runnable == null) throw new NullPointerException();
            this.runnable = runnable;
        }
        public final Void getRawResult() { return null; }
        public final void setRawResult(Void v) { }
        public final boolean exec() { runnable.run(); return true; }
        public final void run() { invoke(); }
        private static final long serialVersionUID = 5232453952276885070L;
    }

    /**
     * Adaptor for Runnables in which failure forces worker exception
     */
    static final class RunnableExecuteAction extends ForkJoinTask<Void> {
        final Runnable runnable;
        RunnableExecuteAction(Runnable runnable) {
            if (runnable == null) throw new NullPointerException();
            this.runnable = runnable;
        }
        public final Void getRawResult() { return null; }
        public final void setRawResult(Void v) { }
        public final boolean exec() { runnable.run(); return true; }
        void internalPropagateException(Throwable ex) {
            rethrow(ex); // rethrow outside exec() catches.
        }
        private static final long serialVersionUID = 5232453952276885070L;
    }

    /**
     * Adaptor for Callables
     */
    static final class AdaptedCallable<T> extends ForkJoinTask<T>
        implements RunnableFuture<T> {
        final Callable<? extends T> callable;
        T result;
        AdaptedCallable(Callable<? extends T> callable) {
            if (callable == null) throw new NullPointerException();
            this.callable = callable;
        }
        public final T getRawResult() { return result; }
        public final void setRawResult(T v) { result = v; }
        public final boolean exec() {
            try {
                result = callable.call();
                return true;
            } catch (Error err) {
                throw err;
            } catch (RuntimeException rex) {
                throw rex;
            } catch (Exception ex) {
                throw new RuntimeException(ex);
            }
        }
        public final void run() { invoke(); }
        private static final long serialVersionUID = 2838392045355241008L;
    }

    /**
     * Returns a new {@code ForkJoinTask} that performs the {@code run}
     * method of the given {@code Runnable} as its action, and returns
     * a null result upon {@link #join}.
     *
     * @param runnable the runnable action
     * @return the task
     */
    public static ForkJoinTask<?> adapt(Runnable runnable) {
        return new AdaptedRunnableAction(runnable);
    }

    /**
     * Returns a new {@code ForkJoinTask} that performs the {@code run}
     * method of the given {@code Runnable} as its action, and returns
     * the given result upon {@link #join}.
     *
     * @param runnable the runnable action
     * @param result the result upon completion
     * @param <T> the type of the result
     * @return the task
     */
    public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
        return new AdaptedRunnable<T>(runnable, result);
    }

    /**
     * Returns a new {@code ForkJoinTask} that performs the {@code call}
     * method of the given {@code Callable} as its action, and returns
     * its result upon {@link #join}, translating any checked exceptions
     * encountered into {@code RuntimeException}.
     *
     * @param callable the callable action
     * @param <T> the type of the callable's result
     * @return the task
     */
    public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
        return new AdaptedCallable<T>(callable);
    }

    // Serialization support

    private static final long serialVersionUID = -7721805057305804111L;

    /**
     * Saves this task to a stream (that is, serializes it).
     *
     * @param s the stream
     * @throws java.io.IOException if an I/O error occurs
     * @serialData the current run status and the exception thrown
     * during execution, or {@code null} if none
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        s.defaultWriteObject();
        s.writeObject(getException());
    }

    /**
     * Reconstitutes this task from a stream (that is, deserializes it).
     * @param s the stream
     * @throws ClassNotFoundException if the class of a serialized object
     *         could not be found
     * @throws java.io.IOException if an I/O error occurs
     */
    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
        s.defaultReadObject();
        Object ex = s.readObject();
        if (ex != null)
            setExceptionalCompletion((Throwable)ex);
    }

    // Unsafe mechanics
    private static final Unsafe U;
    private static final long STATUS;

    static {
        exceptionTableLock = new ReentrantLock();
        exceptionTableRefQueue = new ReferenceQueue<Object>();
        exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY];
        try {
            final Field f = Unsafe.class.getDeclaredField ("theUnsafe");
            f.setAccessible (true);
            U = (Unsafe) f.get (null);
            Class<?> k = ForkJoinTask.class;
            STATUS = U.objectFieldOffset
                (k.getDeclaredField("status"));
        } catch (Exception e) {
            throw new Error(e);
        }
    }

}


package com.ajjpj.afoundation.collection.immutable;

import com.ajjpj.afoundation.collection.AEquality;
import com.ajjpj.afoundation.function.AFunction1;

import java.util.*;

/**
 * An immutable BTree implementation
 *
 * @author arno
 */
public abstract class ABTreeMap<K, V> extends AbstractAMap<K,V> {
    public final ABTreeSpec spec;
    transient private Integer cachedHashcode = null; // intentionally not volatile: This class is immutable, so recalculating per thread works

    @SuppressWarnings ("unchecked")
    public static <K, V> ABTreeMap<K, V> empty (ABTreeSpec spec) {
        return new LeafNode (spec, new Object[0], new Object[0]);
    }

    ABTreeMap (ABTreeSpec spec) {
        this.spec = spec;
    }

    public abstract AOption<V> get (K key);
//    public Iterable<K> keys ();
//    public Iterable<V> values ();
//    public Iterable<K> keys (K keyMin, K keyMax);
//    public Iterable<V> values (K keyMin, K keyMax);

    @SuppressWarnings ("unchecked")
    public ABTreeMap<K,V> updated (K key, V value) {
        final UpdateResult result = _updated (key, value);

        if (result.optRight == null) {
            return result.left;
        }

        // This is the only place where the tree depth can grow.
        // The 'minimum number of children' constraint does not apply to root nodes.
        return new IndexNode (spec, new Object[] {result.separator}, new ABTreeMap[] {result.left, result.optRight});
    }

    @SuppressWarnings ("unchecked")
    @Override public ABTreeMap<K,V> removed (K key) {
        final RemoveResult removeResult = _removed (key, null);
        if (removeResult.underflowed &&
                removeResult.newNode instanceof IndexNode &&
                ((IndexNode) removeResult.newNode).children.length == 1) {
            return ((IndexNode) removeResult.newNode).children[0];
        }
        return _removed (key, null).newNode;
    }

    abstract UpdateResult _updated (Object key, Object value);
    abstract RemoveResult _removed (Object key, Object leftSeparator);
    abstract UpdateResult merge (ABTreeMap rightNeighbour, Object separator);

    @Override public ASet<K> keys () {
        return ABTreeSet.create (this);
    }

    @Override public AMap<K, V> clear () {
        return empty (spec);
    }
    @Override public AEquality keyEquality () {
        return new AEquality.ComparatorBased (spec.comparator);
    }

    @Override public Iterator<AMapEntry<K, V>> iterator () {
        return new BTreeIterator<> (this);
    }

    private static class BTreeIterator<K,V> implements Iterator<AMapEntry<K,V>>, AMapEntry<K,V> {
        private final Deque<Object> stack = new ArrayDeque<> ();

        private K curKey;
        private V curValue;

        public BTreeIterator (ABTreeMap root) {
            if (! root.isEmpty ()) {
                stack.push (root);
            }
        }

        @Override public K getKey () {
            return curKey;
        }
        @Override public V getValue () {
            return curValue;
        }

        @Override public boolean hasNext () {
            return !stack.isEmpty ();
        }

        @SuppressWarnings ("unchecked")
        @Override public AMapEntry<K, V> next () {
            Object next;

            while (true) {
                next = stack.pop ();

                if (next instanceof LeafNode) {
                    final LeafNode leafNode = (LeafNode) next;
                    for (int i=0; i<leafNode.size (); i++) {
                        stack.push (leafNode.values[i]); // push key and value separately to avoid creating temporary object
                        stack.push (leafNode.keys[i]);
                    }
                }
                else if (next instanceof IndexNode) {
                    final IndexNode indexNode = (IndexNode) next;
                    for (ABTreeMap child: indexNode.children) {
                        stack.push (child);
                    }
                }
                else {
                    curKey = (K) next;
                    curValue = (V) stack.pop ();
                    return this;
                }
            }
        }

        @Override public void remove () {
            throw new UnsupportedOperationException ();
        }
    }
}


package com.ajjpj.afoundation.concurrent;

import com.ajjpj.afoundation.collection.immutable.AList;
import com.ajjpj.afoundation.collection.immutable.AOption;
import com.ajjpj.afoundation.collection.immutable.ATry;
import com.ajjpj.afoundation.collection.tuples.ATuple2;
import com.ajjpj.afoundation.function.*;
import com.ajjpj.afoundation.util.AUnchecker;

import java.util.NoSuchElementException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;

class AFutureImpl<T> implements ASettableFuture<T> {
    private final AThreadPool internalThreadPool;
    private final AtomicReference<State<T>> state = new AtomicReference<> (new State<> (null, AList.nil ()));

    public AFutureImpl (AThreadPool internalThreadPool) {
        this.internalThreadPool = internalThreadPool;
    }

    public static <T> AFutureImpl<T> fromTry (AThreadPool tp, ATry<T> o) {
        final AFutureImpl<T> result = new AFutureImpl<> (tp);
        result.complete (o);
        return result;
    }

    @Override public AFuture<T> onComplete (AThreadPool tp, AStatement1<ATry<T>, ?> handler) {
        State<T> before, after;
        do {
            before = state.get ();
            if (before.isComplete ()) {
                fireListener (tp, handler, before.value);
                return this;
            }
            after = before.withListener (tp, handler);
        }
        while (! state.compareAndSet (before, after));
        return this;
    }

    @Override public boolean isComplete () {
        return state.get ().isComplete ();
    }

    @Override public AOption<ATry<T>> optValue () {
        return AOption.fromNullable (state.get ().value);
    }

    @Override public void await (long atMost, TimeUnit timeUnit) throws TimeoutException, InterruptedException {
        final CompletionLatch l = new CompletionLatch ();
        onComplete (AThreadPool.SYNC_THREADPOOL, x -> l.releaseShared (1));
        if (! l.tryAcquireNanos (1, timeUnit.toNanos (atMost))) {
            throw new TimeoutExceptionWithoutStackTrace ();
        }
    }

    @Override public T value (long atMost, TimeUnit timeUnit) throws TimeoutException, InterruptedException {
        await (atMost, timeUnit);
        return optValue ().get ().getValue ();
    }

    @Override public AFuture<Throwable> inverse() {
        final AFutureImpl<Throwable> result = new AFutureImpl<> (AThreadPool.SYNC_THREADPOOL);

        onComplete (AThreadPool.SYNC_THREADPOOL, res -> {
            result.complete (res.inverse ());
        });

        return result;
    }

    @Override public void complete (ATry<T> o) {
        if (!tryComplete (o)) throw new IllegalStateException ("trying to complete an already completed future");
    }

    private void fireListener (AThreadPool tp, AStatement1<ATry<T>, ?> f, ATry<T> value) {
        tp.submit (() -> {
            try {
                f.apply (value);
            }
            catch (Throwable th) {
                AUnchecker.throwUnchecked (th);
            }
        });
    }

    @Override public boolean tryComplete (ATry<T> o) {
        State<T> before, after;

        do {
            before = state.get ();
            if (before.isComplete ()) return false;

            // set the result, and remove all listeners at the same time
            after = new State<> (o, AList.nil ());
        }
        while (! state.compareAndSet (before, after));

        // fire all listeners registered *before* the call to complete
        before.listeners.foreach (l -> fireListener (l._1, l._2, o));

        // ... and fire all listeners registered concurrently. After this call, new listeners will be executed immediately rather than stored, so this is sufficient
        state.get().listeners.foreach (l -> fireListener (l._1, l._2, o));

        return true;
    }

    //TODO completeWith, tryCompleteWith

//    @Override public <S> AFuture<S> transform (AThreadPool tp, AFunction1<T, S, ?> s, AFunction1<Throwable, Throwable, ?> t) {
//        final AFutureImpl<S> result = new AFutureImpl<> ();
//
//        onComplete (tp, res -> {
//            TODO NonFatal?!
//        });
//
//        return result;
//    }

    @Override public <S> AFuture<S> map (AThreadPool tp, AFunction1<T, S, ?> f) {
        final AFutureImpl<S> result = new AFutureImpl<> (tp);

        onComplete (tp, v -> {
            try {
                result.complete (v.map (f));
            }
            catch (Throwable th) {
                result.completeAsFailure (th);
            }
        });

        return result;
    }

    @Override public <S> AFuture<S> flatMap (AThreadPool tp, AFunction1<T, AFuture<S>, ?> f) {
        final AFutureImpl<S> result = new AFutureImpl<> (tp);

        onComplete (tp, v -> {
            if (v.isFailure()) {
                //noinspection unchecked
                result.complete ((ATry<S>) v);
            }
            else {
                f.apply (v.getValue()).onComplete (tp, result::complete); //TODO Scala: NonFatal vs. Fatal exceptions?!
            }
        });

        return result;
    }

    @Override public AFuture<T> filter (AThreadPool tp, APredicate<T, ?> f) {
        return map (tp, x -> {
            if (f.apply (x)) return x;
            else throw new NoSuchElementException ();
        });
    }

    @Override public <S> AFuture<S> collect (AThreadPool tp, APartialFunction<T, S, ?> f) {
        return map (tp, x -> {
            if (f.isDefinedAt (x)) return f.apply (x);
            else throw new NoSuchElementException ();
        });
    }

    @Override public AFuture<T> recover (AThreadPool tp, APartialFunction<Throwable, T, ?> f) {
        final AFutureImpl<T> result = new AFutureImpl<> (tp);
        onComplete (tp, x -> result.complete (x.recover (f)));
        return result;
    }

    @Override public AFuture<T> recoverWith (AThreadPool tp, APartialFunction<Throwable, AFuture<T>, ?> f) {
        final AFutureImpl<T> result = new AFutureImpl<> (tp);

        onSuccess (AThreadPool.SYNC_THREADPOOL, result::completeAsSuccess);
        onFailure (AThreadPool.SYNC_THREADPOOL, (AStatement1<Throwable, Throwable>) th -> {
            if (!f.isDefinedAt (th)) result.completeAsFailure (th);
            else {
                f.apply (th).onComplete (tp, result::complete);
            }
        });

        return result;
    }

    @Override public <S> AFuture<ATuple2<T, S>> zip (AFuture<S> that) {
        final AFutureImpl<ATuple2<T,S>> result = new AFutureImpl<> (internalThreadPool);
        onComplete (internalThreadPool, first -> {
            if (first.isFailure ()) {
                //noinspection unchecked
                result.complete ((ATry) first);
            }
            else {
                that.onComplete (internalThreadPool, second -> {
                    result.complete (second.map (v -> new ATuple2<> (first.getValue (), v)));
                });
            }
        });
        return result;
    }

    @Override public AFuture<T> fallbackTo (AFuture<T> that) {
        final AFutureImpl<T> result = new AFutureImpl<> (internalThreadPool);
        onComplete (internalThreadPool, first -> {
            if (first.isSuccess()) result.complete (first);
            else {
                that.onComplete (internalThreadPool, second -> {
                    if (second.isSuccess ()) result.complete (second);
                    else result.complete (first); // if both failed, complete with the first AFuture's throwable
                });
            }
        });
        return result;
    }

    @Override public AFuture<T> andThen (AThreadPool tp, APartialStatement<ATry<T>, ?> f) {
        final AFutureImpl<T> result = new AFutureImpl<> (tp);
        onComplete (tp, v -> {
            try {
                if (f.isDefinedAt (v)) f.apply (v);
            }
            finally {
                result.complete (v);
            }
        });
        return result;
    }

    static class State<T> {
        final ATry<T> value;
        final AList<ATuple2<AThreadPool, AStatement1<ATry <T>, ?>>> listeners;

        State (ATry<T> value, AList<ATuple2<AThreadPool, AStatement1<ATry<T>, ?>>> listeners) {
            this.value = value;
            this.listeners = listeners;
        }

        State<T> withListener (AThreadPool tp, AStatement1<ATry<T>, ?> l) {
            return new State<> (value, listeners.cons (new ATuple2<> (tp, l)));
        }

        boolean isComplete() {
            return value != null;
        }

        @Override public String toString () {
            return "State{" +
                    "value=" + value +
                    ", listeners=" + listeners +
                    '}';
        }
    }

    static class CompletionLatch extends AbstractQueuedSynchronizer {
        @Override protected int tryAcquireShared (int ignored) {
            return getState () == 0 ? 1 : -1;
        }

        @Override protected boolean tryReleaseShared (int ignored) {
            setState (1);
            return true;
        }
    }
}


package com.ajjpj.afoundation.io;

import com.ajjpj.afoundation.function.AStatement1;

import java.io.*;
import java.nio.charset.Charset;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Locale;

/**
 * This class is a collection of helper methods for manually writing JSON to an OutputStream.

 *

 * For details on the JSON spec, see http://json.org
 *
 * @author arno
 */
public class AJsonSerHelper {
    public static final Charset UTF_8 = Charset.forName ("UTF-8");

    private static final int[] TEN_POW = new int[] {1, 10, 100, 1_000, 10_000, 100_000, 1000_000, 10_000_000, 100_000_000, 1_000_000_000};
    private static final String[] PATTERNS = new String[] {"0", "0.0", "0.00", "0.000", "0.0000", "0.00000", "0.000000", "0.0000000", "0.00000000", "0.000000000"};
    private static final DecimalFormatSymbols DECIMAL_FORMAT_SYMBOLS = new DecimalFormatSymbols (Locale.US);

    protected final Writer out;
    private final Deque<JsonSerState> state = new ArrayDeque<> ();

    public AJsonSerHelper (OutputStream out) {
        this.out = new OutputStreamWriter (out, UTF_8);
        state.push (JsonSerState.initial);
    }

    public void startObject () throws IOException {
        checkAcceptsValueAndPrefixComma ();
        state.push (JsonSerState.startOfObject);
        out.write ("{");
    }

    public void endObject () throws IOException {
        checkInObject ();
        state.pop ();
        out.write ("}");
        afterValueWritten ();
    }

    public void writeKey (String key) throws IOException {
        if (!state ().acceptsKey) {
            throw new IllegalStateException ("state " + state () + " does not accept a key");
        }
        if (state () == JsonSerState.inObject) {
            writeCommaInObject ();
        }
        _writeStringLiteral (key);
        writeColonAfterKey ();
        state.push (JsonSerState.afterKey);
    }

    public void startArray () throws IOException {
        checkAcceptsValueAndPrefixComma ();
        state.push (JsonSerState.startOfArray);
        out.write ("[");
    }

    public void endArray () throws IOException {
        checkInArray ();
        state.pop ();
        out.write ("]");
        afterValueWritten ();
    }

    public void writeStringLiteral (String s) throws IOException {
        if (s == null) {
            writeNullLiteral ();
            return;
        }

        checkAcceptsValueAndPrefixComma ();
        _writeStringLiteral (s);
        afterValueWritten ();
    }

    private void _writeStringLiteral (String s) throws IOException {
        out.write ('"');
        for (int i = 0; i < s.length (); i++) {
            final char ch = s.charAt (i);

            if (ch == '"') {
                out.write ("\\\"");
            }
            else if (ch == '\\') {
                out.write ("\\\\");
            }
            else if (ch < 16) {
                out.write ("\\u000" + Integer.toHexString (ch));
            }
            else if (ch < 32) {
                out.write ("\\u00" + Integer.toHexString (ch));
            }
            else {
                out.write (ch);
            }
        }

        out.write ('"');
    }

    public void writeNumberLiteral (long value, int numFracDigits) throws IOException {
        checkAcceptsValueAndPrefixComma ();

        if (value < 0) {
            out.write ('-');
            value = -value;
        }

        if (numFracDigits == 0) {
            out.write (String.valueOf (value));
        }
        else {
            final long intPart = value / TEN_POW[numFracDigits];
            final String fracPart = String.valueOf (1_000_000_000 + value % TEN_POW[numFracDigits]).substring (10 - numFracDigits, 10);

            out.write (String.valueOf (intPart));
            out.write (".");
            out.write (fracPart);
        }

        afterValueWritten ();
    }

    public void writeNumberLiteral (double value, int numFracDigits) throws IOException {
        checkAcceptsValueAndPrefixComma ();
        out.write (new DecimalFormat (PATTERNS[numFracDigits], DECIMAL_FORMAT_SYMBOLS).format (value));
        afterValueWritten ();
    }

    public void writeBooleanLiteral (boolean value) throws IOException {
        checkAcceptsValueAndPrefixComma ();
        out.write (String.valueOf (value));
        afterValueWritten ();
    }

    public void writeNullLiteral () throws IOException {
        checkAcceptsValueAndPrefixComma ();
        out.write ("null");
        afterValueWritten ();
    }

    //----------------------------------------- convenience API

    public void writeIntLiteral (int value) throws IOException {
        writeNumberLiteral (value, 0);
    }
    public void writeLongLiteral (long value) throws IOException {
        writeNumberLiteral (value, 0);
    }

    public void writeStringArray (Iterable<String> values) throws IOException {
        startArray ();
        for (String el: values) writeStringLiteral (el);
        endArray ();
    }

    public void writeStringField (String key, String value) throws IOException {
        writeKey (key);
        writeStringLiteral (value);
    }
    public void writeBooleanField (String key, Boolean value) throws IOException {
        writeKey (key);
        if (value == null) writeNullLiteral ();
        else writeBooleanLiteral (value);
    }
    public void writeIntField (String key, Integer value) throws IOException {
        writeKey (key);
        if (value == null) writeNullLiteral ();
        else writeIntLiteral (value);
    }
    public void writeLongField (String key, Long value) throws IOException {
        writeKey (key);
        if (value == null) writeNullLiteral ();
        else writeLongLiteral (value);
    }

    /**
     * This is a convenience method for building simple JSON strings. It passes an AJsonSerHelper to a callback and
     *  builds a string based on what the callback does with it.
     */
    public static <E extends Throwable> String buildString (AStatement1<AJsonSerHelper, E> code) throws E {
        final ByteArrayOutputStream baos = new ByteArrayOutputStream ();
        code.apply (new AJsonSerHelper (baos));
        return new String (baos.toByteArray (), UTF_8);
    }

    //----------------------------------------- helper methods

    protected void writeCommaInObject () throws IOException {
        out.write (",");
    }

    protected void writeCommaInArray () throws IOException {
        out.write (",");
    }

    protected void writeColonAfterKey () throws IOException {
        out.write (":");
    }

    protected void checkAcceptsValueAndPrefixComma () throws IOException {
        if (!state ().acceptsValue) {
            throw new IllegalStateException ("state " + state () + " does not accept a value");
        }
        if (state () == JsonSerState.inArray) {
            writeCommaInArray ();
        }
    }

    protected void afterValueWritten () throws IOException {
        if (state () == JsonSerState.afterKey) {
            state.pop ();
        }
        switch (state ()) {
            case startOfArray:
                replaceState (JsonSerState.inArray);
                break;
            case startOfObject:
                replaceState (JsonSerState.inObject);
                break;
            case initial:
                replaceState (JsonSerState.finished);
                out.flush ();
                break;
            default:
        }
    }

    private void checkInObject () {
        if (state () != JsonSerState.inObject && state () != JsonSerState.startOfObject) {
            throw new IllegalStateException ("not in an object");
        }
    }

    private void checkInArray () {
        if (state () != JsonSerState.inArray && state () != JsonSerState.startOfArray) {
            throw new IllegalStateException ("not in an array");
        }
    }

    private void replaceState (JsonSerState newState) {
        state.pop ();
        state.push (newState);
    }

    protected JsonSerState state () {
        return state.peek ();
    }
}