omsbuff_getslot.c

linux下的rtp的实例源代码

/* * 
 *  $Id: OMSbuff_getslot.c 333 2006-03-31 18:40:05Z shawill $
 *  
 *  This file is part of Fenice
 *
 *  Fenice -- Open Media Server
 *
 *  Copyright (C) 2004 by
 *  	
 *	- Giampaolo Mancini	<[e-mail]>
 *	- Francesco Varano	<[e-mail]>
 *	- Marco Penno		<[e-mail]>
 *	- Federico Ridolfo	<[e-mail]>
 *	- Eugenio Menegatti 	<[e-mail]>
 *	- Stefano Cau
 *	- Giuliano Emma
 *	- Stefano Oldrini
 * 
 *  Fenice 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.
 *
 *  Fenice 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 Fenice; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *  
 * */
#include <fenice/bufferpool.h>


/*! \brief get a new empty slot from bufferpool.
 *
 * It do NOT mark the slot as busy, this action will be performed by
 * OMSbuff_write that MUST be called at the end of operations with the obtained
 * slot.
 *
 * \return empty slot.
 */
OMSSlot *OMSbuff_getslot(OMSBuffer *buffer)
{
	OMSSlot *slot = &buffer->slots[buffer->control->write_pos]; // lock not needed here
	// uint64 curr_seq = slot->slot_seq;
	OMSSlot *valid_read_pos = &buffer->slots[buffer->control->valid_read_pos];
	double ts;
	
	OMSbuff_lock(buffer);
	
	if (OMSbuff_shm_refresh(buffer))
		return NULL;
	
	if(buffer->slots[slot->next].refs > 0) {
		// printf("must add slot\n");
		if ( !(slot=OMSbuff_addpage(buffer, slot)) ) {
			OMSbuff_unlock(buffer);
			return NULL;
		}
	} else {
		slot = &buffer->slots[slot->next];
		// write_pos reaches valid_read_pos, we "push" it
		if ( (valid_read_pos->slot_seq) && (valid_read_pos == slot) ) {
			for (ts=valid_read_pos->timestamp;\
				(buffer->slots[valid_read_pos->next].slot_seq) && (ts==valid_read_pos->timestamp);\
				ts=valid_read_pos->timestamp, valid_read_pos=&buffer->slots[valid_read_pos->next]);
			buffer->control->valid_read_pos = OMStoSlotPtr(buffer, valid_read_pos);
		}
	}
	
	OMSbuff_unlock(buffer);

	return slot; 
}