/*************************************************************************

 *                                                                       *

 * 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.                     *

 *                                                                       *

 *************************************************************************/

#include <ode/common.h>

#include <ode/error.h>

#include <ode/memory.h>

#include "obstack.h"

//****************************************************************************

// macros and constants

#define ROUND_UP_OFFSET_TO_EFFICIENT_SIZE(arena,ofs) \

  ofs = (size_t) (dEFFICIENT_SIZE( ((intP)(arena)) + ofs ) - ((intP)(arena)) );

#define MAX_ALLOC_SIZE \

  ((size_t)(dOBSTACK_ARENA_SIZE - sizeof (Arena) - EFFICIENT_ALIGNMENT + 1))

//****************************************************************************

// dObStack

dObStack::dObStack()

{

  first = 0;

  last = 0;

  current_arena = 0;

  current_ofs = 0;

}

dObStack::~dObStack()

{

  // free all arenas

  Arena *a,*nexta;

  a = first;

  while (a) {

    nexta = a->next;

    dFree (a,dOBSTACK_ARENA_SIZE);

    a = nexta;

  }

}

void *dObStack::alloc (int num_bytes)

{

  // allocate or move to a new arena if necessary

  if (!first) {

    // allocate the first arena if necessary

    first = last = (Arena *) dAlloc (dOBSTACK_ARENA_SIZE);

    first->next = 0;

    first->used = sizeof (Arena);

    ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (first,first->used);

  }

  else {

    // we already have one or more arenas, see if a new arena must be used

    if ((last->used + num_bytes) > dOBSTACK_ARENA_SIZE) {

      if (!last->next) {

	last->next = (Arena *) dAlloc (dOBSTACK_ARENA_SIZE);

	last->next->next = 0;

      }

      last = last->next;

      last->used = sizeof (Arena);

      ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (last,last->used);

    }

  }

  // allocate an area in the arena

  char *c = ((char*) last) + last->used;

  last->used += num_bytes;

  ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (last,last->used);

  return c;

}

void dObStack::freeAll()

{

  last = first;

  if (first) {

    first->used = sizeof(Arena);

    ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (first,first->used);

  }

}

void *dObStack::rewind()

{

  current_arena = first;

  current_ofs = sizeof (Arena);

  if (current_arena) {

    ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (current_arena,current_ofs)

    return ((char*) current_arena) + current_ofs;

  }

  else return 0;

}

void *dObStack::next (int num_bytes)

{

  // this functions like alloc, except that no new storage is ever allocated

  if (!current_arena) return 0;

  current_ofs += num_bytes;

  ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (current_arena,current_ofs);

  if (current_ofs >= current_arena->used) {

    current_arena = current_arena->next;

    if (!current_arena) return 0;

    current_ofs = sizeof (Arena);

    ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (current_arena,current_ofs);

  }

  return ((char*) current_arena) + current_ofs;

}