/*

 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

#ifndef SHARE_GC_G1_G1FREEIDSET_HPP

#define SHARE_GC_G1_G1FREEIDSET_HPP

#include "runtime/semaphore.hpp"

#include "utilities/globalDefinitions.hpp"

// Represents a set of small integer ids, from which elements can be

// temporarily allocated for exclusive use.  The ids are in a

// contiguous range from 'start' to 'start + size'.  Used to obtain a

// distinct worker_id value for a mutator thread that doesn't normally

// have such an id.

class G1FreeIdSet {

  Semaphore _sem;

  uint* _next;

  uint _start;

  uint _size;

  uintx _head_index_mask;

  volatile uintx _head;

  uint head_index(uintx head) const;

  uintx make_head(uint index, uintx old_head) const;

  // Noncopyable.

  G1FreeIdSet(const G1FreeIdSet&);

  G1FreeIdSet& operator=(const G1FreeIdSet&);

public:

  G1FreeIdSet(uint start, uint size);

  ~G1FreeIdSet();

  // Returns an unclaimed parallel id (waiting for one to be released if

  // necessary).  Must not safepoint while holding a claimed id.

  uint claim_par_id();

  void release_par_id(uint id);

  struct TestSupport;           // For unit test access.

};

#endif // SHARE_GC_G1_G1FREEIDSET_HPP