/*

 * Copyright (c) 2020 Red Hat, Inc.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2

 * of the License, or (at your option) any later version.

 * 

 * This program 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 for more details.

 * 

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

 * 02110-1301, USA. 

 *

 * $Id: //eng/vdo-releases/aluminum/src/c++/vdo/base/slabIterator.h#1 $

 */

#ifndef SLAB_ITERATOR_H

#define SLAB_ITERATOR_H

#include "slab.h"

#include "types.h"

/**

 * SlabIterator is a structure for iterating over a set of slabs.

 **/

typedef struct {

  Slab      **slabs;

  Slab       *next;

  SlabCount   end;

  SlabCount   stride;

} SlabIterator;

/**

 * Return a SlabIterator initialized to iterate over an array of slabs

 * with a given stride. Iteration always occurs from higher to lower numbered

 * slabs.

 *

 * @param slabs  The array of slabs

 * @param start  The number of the slab to start iterating from

 * @param end    The number of the last slab which may be returned

 * @param stride The difference in slab number between successive slabs

 *

 * @return an initialized iterator structure

 **/

static inline SlabIterator iterateSlabs(Slab      **slabs,

                                        SlabCount   start,

                                        SlabCount   end,

                                        SlabCount   stride)

{

  return (SlabIterator) {

    .slabs  = slabs,

    .next   = (((slabs == NULL) || (start < end)) ? NULL : slabs[start]),

    .end    = end,

    .stride = stride,

  };

}

/**

 * Check whether another Slab would be returned by the iterator.

 *

 * @param iterator  The iterator to poll

 *

 * @return true if the next call to nextSlab

 *         will return a Slab

 **/

static inline bool hasNextSlab(const SlabIterator *iterator)

{

  return (iterator->next != NULL);

}

/**

 * Get the next Slab, advancing the iterator.

 *

 * @param iterator  The iterator over the Slab chain

 *

 * @return the next Slab or NULL if the array of slabs is empty

 *         or if all the appropriate Slabs have been returned

 **/

static inline Slab *nextSlab(SlabIterator *iterator)

{

  Slab *slab = iterator->next;

  if ((slab == NULL)

      || (slab->slabNumber < iterator->end + iterator->stride)) {

    iterator->next = NULL;

  } else {

    iterator->next = iterator->slabs[slab->slabNumber - iterator->stride];

  }

  return slab;

}

#endif // SLAB_ITERATOR_H