/* * 
 * 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 internal function used to add a page of slots (of BPBUFF_MEM_PAGE size).
 * WARNING: the function assumes that the caller (bp_write or bp_getslot) locked the buffer mutex
 * @return the first BPSlot of new added page of slots.
 * */
BPSlot *bp_addpage(BPBuffer * buffer, BPSlot * prev)
{
    BPSlot *added;
    unsigned int i;
    ptrdiff_t prev_diff;

    switch (buffer->type) {
    case buff_shm:
        prev_diff = prev - buffer->slots;
        added = bp_shm_addpage(buffer);
        prev = buffer->slots + prev_diff;

        buffer->slots[buffer->known_slots - 1].next = prev->next;    // last added slot in shm new page is linked to the prev->next in old queue

        bp_log(FNC_LOG_DEBUG,
            "BPSlots page added in SHM memory (%u slots - %s)\n",
            buffer->known_slots, buffer->filename);
        break;
    case buff_local:
        prev_diff = prev - buffer->slots;
        if (!(added = realloc(buffer->slots, (buffer->control->nslots +
                  BPBUFF_MEM_PAGE) * sizeof(BPSlot))))
            return NULL;
        buffer->slots = added;

        prev = buffer->slots + prev_diff;
        // init new slots
        for (i = buffer->control->nslots;
             i < buffer->control->nslots + BPBUFF_MEM_PAGE - 1; i++) {
            added[i].refs = 0;
            added[i].slot_seq = 0;
            added[i].next = i + 1;
        }
        // last slot
        added[i].refs = 0;
        added[i].slot_seq = 0;
        added[i].next = prev->next;

        added = &added[buffer->control->nslots];
        buffer->control->nslots += BPBUFF_MEM_PAGE;
        buffer->known_slots = buffer->control->nslots;

        bp_log(FNC_LOG_DEBUG,
            "BPSlots page added in local bufferpool (%u slots)\n",
            buffer->known_slots);
        break;
    default:
        return NULL;
        break;
    }

    prev->next = BPtoSlotPtr(buffer, added);

    return added;
}