* http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck/JSR166TestCase.java?revision=1.90
 * (We have made some trivial local modifications (commented out
 * uncompilable code).)
 */

package com.google.common.util.concurrent;

 */
public class MonitorBasedPriorityBlockingQueue<E> extends AbstractQueue<E>
    implements BlockingQueue<E> {

  // Based on revision 1.55 of PriorityBlockingQueue by Doug Lea, from
  // http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/main/java/util/concurrent/

  private static final long serialVersionUID = 5595510919245408276L;

  final PriorityQueue<E> q;
  final Monitor monitor = new Monitor(true);

public class MonitorBasedArrayBlockingQueue<E> extends AbstractQueue<E>
    implements BlockingQueue<E> {

  // Based on revision 1.58 of ArrayBlockingQueue by Doug Lea, from
  // http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/main/java/util/concurrent/

  /** The queued items */
  final E[] items;
  /** items index for next take, poll or remove */
  int takeIndex;
  /** items index for next put, offer, or add. */

      // But in gcd(a - b, b), a - b is even and b is odd, so we can divide out powers of two.

      // We bend over backwards to avoid branching, adapting a technique from
      // http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax

      long delta = a - b; // can't overflow, since a and b are nonnegative

      long minDeltaOrZero = delta & (delta >> (Long.SIZE - 1));
      // equivalent to Math.min(delta, 0)

    // There are several well-known algorithms for rotating part of an array (or, equivalently,
    // exchanging two blocks of memory). This classic text by Gries and Mills mentions several:
    // https://ecommons.cornell.edu/bitstream/handle/1813/6292/81-452.pdf.
    // (1) "Reversal", the one we have here.
    // (2) "Dolphin". If we're rotating an array a of size n by a distance of d, then element a[0]

  //    definitely observe all earlier writes, but we still have no guarantee that done() would see
  //    the initial write (just stronger guarantees if it does).
  //
  // See: http://cs.oswego.edu/pipermail/concurrency-interest/2015-January/013800.html
  // For a (long) discussion about this specific issue and the general futility of life.
  //