/*

 * Copyright (c) 2001, 2010, 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_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP

#define SHARE_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP

#include "memory/genOopClosures.hpp"

#include "memory/generation.hpp"

#include "runtime/os.hpp"

#include "utilities/taskqueue.hpp"

// A BufferingOops closure tries to separate out the cost of finding roots

// from the cost of applying closures to them.  It maintains an array of

// ref-containing locations.  Until the array is full, applying the closure

// to an oop* merely records that location in the array.  Since this

// closure app cost is small, an elapsed timer can approximately attribute

// all of this cost to the cost of finding the roots.  When the array fills

// up, the wrapped closure is applied to all elements, keeping track of

// this elapsed time of this process, and leaving the array empty.

// The caller must be sure to call "done" to process any unprocessed

// buffered entriess.

class Generation;

class HeapRegion;

class BufferingOopClosure: public OopClosure {

protected:

  enum PrivateConstants {

    BufferLength = 1024

  };

  StarTask  _buffer[BufferLength];

  StarTask* _buffer_top;

  StarTask* _buffer_curr;

  OopClosure* _oc;

  double      _closure_app_seconds;

  void process_buffer () {

    double start = os::elapsedTime();

    for (StarTask* curr = _buffer; curr < _buffer_curr; ++curr) {

      if (curr->is_narrow()) {

        assert(UseCompressedOops, "Error");

        _oc->do_oop((narrowOop*)(*curr));

      } else {

        _oc->do_oop((oop*)(*curr));

      }

    }

    _buffer_curr = _buffer;

    _closure_app_seconds += (os::elapsedTime() - start);

  }

  template <class T> inline void do_oop_work(T* p) {

    if (_buffer_curr == _buffer_top) {

      process_buffer();

    }

    StarTask new_ref(p);

    *_buffer_curr = new_ref;

    ++_buffer_curr;

  }

public:

  virtual void do_oop(narrowOop* p) { do_oop_work(p); }

  virtual void do_oop(oop* p)       { do_oop_work(p); }

  void done () {

    if (_buffer_curr > _buffer) {

      process_buffer();

    }

  }

  double closure_app_seconds () {

    return _closure_app_seconds;

  }

  BufferingOopClosure (OopClosure *oc) :

    _oc(oc),

    _buffer_curr(_buffer), _buffer_top(_buffer + BufferLength),

    _closure_app_seconds(0.0) { }

};

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP