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obstack.h

/*************************************************************************
 *                                                                       *
 * Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith.       *
 * All rights reserved.  Email: russ@q12.org   Web: www.q12.org          *
 *                                                                       *
 * This library is free software; you can redistribute it and/or         *
 * modify it under the terms of EITHER:                                  *
 *   (1) The GNU Lesser General Public License as published by the Free  *
 *       Software Foundation; either version 2.1 of the License, or (at  *
 *       your option) any later version. The text of the GNU Lesser      *
 *       General Public License is included with this library in the     *
 *       file LICENSE.TXT.                                               *
 *   (2) The BSD-style license that is included with this library in     *
 *       the file LICENSE-BSD.TXT.                                       *
 *                                                                       *
 * This library 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 files    *
 * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     *
 *                                                                       *
 *************************************************************************/

#ifndef _ODE_OBSTACK_H_
#define _ODE_OBSTACK_H_

#include "objects.h" 

// each obstack Arena pointer points to a block of this many bytes
#define dOBSTACK_ARENA_SIZE 16384


struct dObStack : public dBase {
  struct Arena {
    Arena *next;  // next arena in linked list
    int used;           // total number of bytes used in this arena, counting
  };              //   this header

  Arena *first;         // head of the arena linked list. 0 if no arenas yet
  Arena *last;          // arena where blocks are currently being allocated

  // used for iterator
  Arena *current_arena;
  int current_ofs;

  dObStack();
  ~dObStack();

  void *alloc (int num_bytes);
  // allocate a block in the last arena, allocating a new arena if necessary.
  // it is a runtime error if num_bytes is larger than the arena size.

  void freeAll();
  // free all blocks in all arenas. this does not deallocate the arenas
  // themselves, so future alloc()s will reuse them.

  void *rewind();
  // rewind the obstack iterator, and return the address of the first
  // allocated block. return 0 if there are no allocated blocks.

  void *next (int num_bytes);
  // return the address of the next allocated block. 'num_bytes' is the size
  // of the previous block. this returns null if there are no more arenas.
  // the sequence of 'num_bytes' parameters passed to next() during a
  // traversal of the list must exactly match the parameters passed to alloc().
};


#endif


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