omsbuff_shm_addpage.c

linux下的rtp的实例源代码

/* * 
 *  $Id: OMSbuff_shm_addpage.c 326 2006-03-24 17:27:46Z 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 <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>

#include <sys/mman.h>

#include <fenice/bufferpool.h>
#include <fenice/fnc_log.h>

/*!\brief This function adds shared memory page of slots.
 * The function remaps the shared memory according to the new size, but
 * it does NOT link new page to previous existing queue:
 * This is done in OMSbuff_slotadd.
 * WARNING: the function assumes that the caller (OMSbuff_write or OMSbuff_getslot) locked the buffer mutex
 * \return the first OMSSlot of new added page of slots.
 * */
OMSSlot *OMSbuff_shm_addpage(OMSBuffer *buffer)
{
	OMSSlot *added;
	OMSSlot *slots;
	unsigned int i;
	char *shm_file_name;
	int fd;
	struct stat fdstat;
	
	// *** slots mapping in shared memory ***
	if ( !(shm_file_name = fnc_ipc_name(buffer->filename, OMSBUFF_SHM_SLOTSNAME)) ) return NULL;
	
	fd = shm_open(shm_file_name, O_RDWR, 0);
	free(shm_file_name);
	if ( (fd < 0) ) {
		fnc_log(FNC_LOG_ERR, "Could not open POSIX shared memory (OMSSlots): is Felix running?\n");
		return NULL;
	}
	if ( (fstat(fd, &fdstat) < 0) ) {
		fnc_log(FNC_LOG_ERR, "Could not stat %s\n", OMSBUFF_SHM_SLOTSNAME);
		close(fd);
		return NULL;
	}
		
	if ( ((size_t)fdstat.st_size != buffer->control->nslots*sizeof(OMSSlot)) ) {
		fnc_log(FNC_LOG_ERR, "Strange size for shared memory! (not the number of slots reported in control struct)\n");
		close(fd);
		return NULL;
	}			
	if (ftruncate(fd, (buffer->control->nslots + OMSBUFF_SHM_PAGE) * sizeof(OMSSlot))) {
		fnc_log(FNC_LOG_ERR, "Could not set correct size for shared memory object (OMSControl)\n");
		close(fd);
		return NULL;
	}
	if (munmap(buffer->slots, buffer->known_slots * sizeof(OMSSlot))) {
		fnc_log(FNC_LOG_ERR, "Could not unmap previous slots!!!\n");
		close(fd);
		return NULL;
	}
	slots = mmap(NULL, (buffer->control->nslots + OMSBUFF_SHM_PAGE) * sizeof(OMSSlot), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	close(fd);
	if ( slots == MAP_FAILED ) {
		fnc_log(FNC_LOG_FATAL, "SHM: error in mmap\n");
		return NULL;
	}
	
	// inizialization of OMSSlots added
	for (i=buffer->control->nslots; i<buffer->control->nslots+OMSBUFF_SHM_PAGE-1; i++) {
		slots[i].refs = 0;
		slots[i].slot_seq = 0;
		slots[i].next = i + 1;
	}
	slots[i].refs = 0;
	slots[i].slot_seq = 0;
	slots[i].next = -1; // last added slot in shm new page has next slot to NULL: OMSbuff_slotadd will link it correctly.
	
	added = &slots[buffer->control->nslots];	
	buffer->slots = slots;
	buffer->control->nslots += OMSBUFF_SHM_PAGE;
	buffer->known_slots = buffer->control->nslots;
	
	return added;
}