/*

 * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.

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

 *

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

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

 * published by the Free Software Foundation.

 *

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

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

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

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

 * accompanied this code).

 *

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

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

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

 *

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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#ifndef SHARE_VM_JFR_RECORDER_STORAGE_JFRBUFFER_HPP

#define SHARE_VM_JFR_RECORDER_STORAGE_JFRBUFFER_HPP

#include "memory/allocation.hpp"

//

// Represents a piece of committed memory.

//

// u1* _pos <-- next store position

// u1* _top <-- next unflushed position

//

//

// Must be the owner before attempting stores.

// Use acquire() and/or try_acquire() for exclusive access

// to the (entire) buffer (cas identity).

//

// Stores to the buffer should uphold transactional semantics.

// A new _pos must be updated only after all intended stores have completed.

// The relation between _pos and _top must hold atomically,

// e.g. the delta must always be fully parsable.

// _top can move concurrently by other threads but is always <= _pos.

//

class JfrBuffer {

 private:

  JfrBuffer* _next;

  JfrBuffer* _prev;

  const void* volatile _identity;

  u1* _pos;

  mutable const u1* volatile _top;

  u2 _flags;

  u2 _header_size;

  u4 _size;

  const u1* stable_top() const;

  void clear_flags();

 public:

  JfrBuffer();

  bool initialize(size_t header_size, size_t size, const void* id = NULL);

  void reinitialize();

  void concurrent_reinitialization();

  size_t discard();

  JfrBuffer* next() const {

    return _next;

  }

  JfrBuffer* prev() const {

    return _prev;

  }

  void set_next(JfrBuffer* next) {

    _next = next;

  }

  void set_prev(JfrBuffer* prev) {

    _prev = prev;

  }

  const u1* start() const {

    return ((const u1*)this) + _header_size;

  }

  u1* start() {

    return ((u1*)this) + _header_size;

  }

  const u1* end() const {

    return start() + size();

  }

  const u1* pos() const {

    return _pos;

  }

  u1* pos() {

    return _pos;

  }

  u1** pos_address() {

    return (u1**)&_pos;

  }

  void set_pos(u1* new_pos) {

    assert(new_pos <= end(), "invariant");

    _pos = new_pos;

  }

  void set_pos(size_t size) {

    assert(_pos + size <= end(), "invariant");

    _pos += size;

  }

  const u1* top() const;

  void set_top(const u1* new_top);

  const u1* concurrent_top() const;

  void set_concurrent_top(const u1* new_top);

  size_t header_size() const {

    return _header_size;

  }

  size_t size() const {

    return _size * BytesPerWord;

  }

  size_t total_size() const {

    return header_size() + size();

  }

  size_t free_size() const {

    return end() - pos();

  }

  size_t unflushed_size() const;

  bool empty() const {

    return pos() == start();

  }

  const void* identity() const {

    return _identity;

  }

  void clear_identity();

  void acquire(const void* id);

  bool try_acquire(const void* id);

  void release();

  void move(JfrBuffer* const to, size_t size);

  void concurrent_move_and_reinitialize(JfrBuffer* const to, size_t size);

  bool transient() const;

  void set_transient();

  void clear_transient();

  bool lease() const;

  void set_lease();

  void clear_lease();

  bool retired() const;

  void set_retired();

  void clear_retired();

  debug_only(bool acquired_by_self() const;)

};

class JfrAgeNode : public JfrBuffer {

 private:

  JfrBuffer* _retired;

 public:

  JfrAgeNode() : _retired(NULL) {}

  void set_retired_buffer(JfrBuffer* retired) {

    _retired = retired;

  }

  JfrBuffer* retired_buffer() const {

    return _retired;

  }

};

#endif // SHARE_VM_JFR_RECORDER_STORAGE_JFRBUFFER_HPP