// Filename: neverFreeMemory.h
// Created by:  drose (14Jun07)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001 - 2004, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://etc.cmu.edu/panda3d/docs/license/ .
//
// To contact the maintainers of this program write to
// panda3d-general@lists.sourceforge.net .
//
////////////////////////////////////////////////////////////////////

#ifndef NEVERFREEMEMORY_H
#define NEVERFREEMEMORY_H

#include "dtoolbase.h"

#include "mutexImpl.h"
#include <set>

////////////////////////////////////////////////////////////////////
//       Class : NeverFreeMemory
// Description : This class is used to allocate bytes of memory from a
//               pool that is never intended to be freed.  It is
//               particularly useful to support DeletedChain, which
//               allocates memory in just such a fashion.
//
//               When it is known that memory will not be freed, it is
//               preferable to use this instead of the standard
//               malloc() (or global_operator_new()) call, since this
//               will help reduce fragmentation problems in the
//               dynamic heap.  Also, memory allocated from here will
//               exhibit less wasted space.
////////////////////////////////////////////////////////////////////
class EXPCL_DTOOL NeverFreeMemory {
private:
  NeverFreeMemory();

public:
  INLINE static void *alloc(size_t size);

PUBLISHED:
  INLINE static size_t get_total_alloc();
  INLINE static size_t get_total_used();
  INLINE static size_t get_total_unused();

private:
  void *ns_alloc(size_t size);
  INLINE static NeverFreeMemory *get_global_ptr();
  static void make_global_ptr();

private:
  class Page {
  public:
    INLINE Page(void *start, size_t size);
    INLINE bool operator < (const Page &other) const;
    INLINE void *alloc(size_t size);

    unsigned char *_next;
    size_t _remaining;
  };

  typedef set<Page> Pages;
  Pages _pages;

  size_t _total_alloc;
  size_t _total_used;
  MutexImpl _lock;
  static NeverFreeMemory * TVOLATILE _global_ptr;
};

#include "neverFreeMemory.I"

#endif
