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 /*

  * 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.

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  */

 #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

 //

 // const void* _identity <-- acquired by

 //

 // 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;

  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);

   bool acquired_by(const void* id) const;

   bool acquired_by_self() const;

   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();

 };

 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