/*************************************************************************
 *                                                                       *
 * 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 {
    dObStack();
    ~dObStack();

    void *alloc (size_t 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 (size_t 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().

private:
    struct Arena {
        Arena *m_next;	// next arena in linked list
        size_t m_used;		// total number of bytes used in this arena, counting
    };			//   this header

private:
    void *switch_to_arena(Arena *next_arena);

private:
    Arena *m_first;		// head of the arena linked list. 0 if no arenas yet
    Arena *m_last;		// arena where blocks are currently being allocated

    // used for iterator
    Arena *m_current_arena;
    size_t m_current_ofs;
};


#endif
