/* * 
 * This file is part of bufferpool
 *
 * Copyright (C) 2007 by LScube team <team@streaming.polito.it>
 * See AUTHORS for more details
 * 
 * bufferpool is free software; you can redistribute it and/or
 * modify it under the terms of 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.
 *
 * bufferpool 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with bufferpool; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 
 *
 * */

#include <bufferpool.h>

/*! @brief get a new empty slot from bufferpool.
 *
 * It do NOT mark the slot as busy, this action will be performed by
 * bp_write that MUST be called at the end of operations with the obtained
 * slot.
 *
 * @return empty slot.
 */
BPSlot *bp_getslot(BPBuffer * buffer)
{
    BPSlot *slot;

    bp_lock(buffer);

    if (bp_shm_refresh(buffer))
        return NULL;
    
    slot = &buffer->slots[buffer->control->write_pos];

    if (buffer->slots[slot->next].refs > 0) {
        if (!(slot = bp_addpage(buffer, slot))) {
            bp_unlock(buffer);
            return NULL;
        }
    } else {
        slot = &buffer->slots[slot->next];
    }

    bp_unlock(buffer);

    return slot;
}