/* * 
 * 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 <sys/mman.h>

#include <bufferpool.h>

#define RETURN_ERR    do { \
                bp_unlock(cons->buffer); \
                return 1; \
            } while (0)

/* ! move current read position
 *
 * @return 1 on error, 0 otherwise
 * */
int bp_gotreader(BPConsumer * cons)
{
    BPSlot *last_read;
    BPSlot *next;

    bp_lock(cons->buffer);

    if (bp_shm_refresh(cons->buffer))
        RETURN_ERR;

    last_read = BPtoSlot(cons->buffer, cons->last_read_pos);
    next = &cons->buffer->slots[cons->read_pos];

    if (!next->refs || (next->slot_seq < cons->last_seq)) {
        // added some slots?
        if (last_read && cons->buffer->slots[last_read->next].refs
            && (cons->buffer->slots[last_read->next].slot_seq >
            cons->last_seq))
            next = &cons->buffer->slots[last_read->next];
        else
            RETURN_ERR;
    } else if (last_read
           && (cons->buffer->slots[last_read->next].slot_seq <
               next->slot_seq))
        next = &cons->buffer->slots[last_read->next];

    next->refs--;

    cons->last_seq = next->slot_seq;

//      if ( msync(next, sizeof(BPSlot), MS_ASYNC) )
//      if ( msync(cons->buffer->slots, cons->buffer->known_slots * sizeof(BPSlot), MS_ASYNC) )
//              printf("*** slot msync error\n");

    cons->last_read_pos = BPtoSlotPtr(cons->buffer, next);
    cons->read_pos = next->next;

    // cons->read_pos->refs--;
    bp_dump(cons, NULL);
    bp_unlock(cons->buffer);

    // return cons->read_pos;
    return 0;        // next;
}

#undef RETURN_ERR