omsbuff_shm_create.c

linux下的rtp的实例源代码

/* * 
 *  $Id: OMSbuff_shm_create.c 327 2006-03-28 16:14:41Z 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 <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>

#include <sys/mman.h>

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

#define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)

/*! \brief This function creates che shared memory object on the file system.
 *  In order to let different, and independent, processes to access it.
 * WARNING: this function is not used by fenice directly but it is implemented here for completeness.
 * Fenice is just the "consumer" of a shared memory object, while the producer is some other object like felix.
 * */
 // TODO: unlink on error
OMSBuffer *OMSbuff_shm_create(char *shm_name, uint32 buffer_size)
{
	OMSBuffer *buffer;
	OMSSlot *slots;
	OMSControl *control;
	int fd, shm_open_errno;
	uint32 index;
	char *shm_file_name;
	pthread_mutexattr_t mutex_attr;
	
	if (!buffer_size) return NULL;
	
	// *** control struct shared memory object ***
	if ( !(shm_file_name = fnc_ipc_name(shm_name, OMSBUFF_SHM_CTRLNAME)) ) return NULL;
	
	fd = shm_open(shm_file_name, O_RDWR | O_CREAT | O_EXCL, FILE_MODE);
	shm_open_errno = errno;
	if ( (fd < 0) ) {
		switch (shm_open_errno) {
			case EEXIST:
				fnc_log(FNC_LOG_ERR, "SHM object \"%s\" already exists! Perhaps some other apps are using it\n", shm_file_name);
				fnc_log(FNC_LOG_ERR, "TIP: If you are sure none is using it try deleting it manually.\n");
				break;
			case EINVAL:
				fnc_log(FNC_LOG_ERR, "Invalid name (%s) was given for shared memory object\n", shm_file_name);
				break;
			case EACCES:
				fnc_log(FNC_LOG_ERR, "Permission denied for shared memory object\n", shm_file_name);
				break;
			case ENOENT:
				fnc_log(FNC_LOG_ERR, "Could not create\n", shm_file_name);
				break;
			default:
				break;
		}
		fnc_log(FNC_LOG_ERR, "Could not open/create POSIX shared memory %s (OMSControl)\n", shm_file_name);
		free(shm_file_name);
		return NULL;
	}
	free(shm_file_name);
	if (ftruncate(fd, sizeof(OMSControl))) {
		fnc_log(FNC_LOG_ERR, "Could not set correct size for shared memory object (OMSControl)\n");
		close(fd);
		return NULL;
	}
	control = mmap(NULL, sizeof(OMSControl), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	close(fd);
	if ( control == MAP_FAILED ) {
		fnc_log(FNC_LOG_FATAL, "SHM: error in mmap\n");
		return NULL;
	}
	
	// inizialization of OMSControl
	if ( pthread_mutexattr_init(&mutex_attr) || pthread_mutex_init(&control->syn, &mutex_attr) ) {
		munmap(control, sizeof(OMSControl));
		return NULL;
	}
	
	pthread_mutex_lock(&control->syn);
	control->refs = 0;
	control->nslots = buffer_size;
	
	// *** slots mapping in shared memory ***
	if ( !(shm_file_name = fnc_ipc_name(shm_name, OMSBUFF_SHM_SLOTSNAME)) ) return NULL;
	
	fd = shm_open(shm_file_name, O_RDWR | O_CREAT | O_EXCL, FILE_MODE);
	shm_open_errno = errno;
	free(shm_file_name);
	if ( (fd < 0) ) {
		switch (shm_open_errno) {
			case EEXIST:
				fnc_log(FNC_LOG_ERR, "SHM object \"%s\" already exists! Perhaps some other apps are using it\n", shm_file_name);
				fnc_log(FNC_LOG_ERR, "TIP: If you are sure none is using it try deleting it manually.\n");
				break;
			case EINVAL:
				fnc_log(FNC_LOG_ERR, "Invalid name (%s) was given for shared memory object\n", shm_file_name);
				break;
			default:
				break;
		}
		fnc_log(FNC_LOG_ERR, "Could not open/create POSIX shared memory (OMSSlots)\n");
		munmap(control, sizeof(OMSControl));
		return NULL;
	}
	if (ftruncate(fd, buffer_size * sizeof(OMSSlot))) {
		fnc_log(FNC_LOG_ERR, "Could not set correct size for shared memory object (OMSControl)\n");
		close(fd);
		munmap(control, sizeof(OMSControl));
		return NULL;
	}
	slots = mmap(NULL, buffer_size * 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");
		munmap(control, sizeof(OMSControl));
		return NULL;
	}
	
	// inizialization of OMSSlots
	for(index=0; index<buffer_size-1; index++) {
		slots[index].refs = 0;
		slots[index].slot_seq = 0;
		slots[index].next = index + 1; // &(slots[index+1]) - slots;
	}

	slots[index].next = 0; // slots - slots; /*end of the list back to the head*/
	slots[index].slot_seq = 0;
	slots[index].refs = 0; // last slot not yet initialized if for cycle.
	
	control->write_pos = buffer_size-1;
	control->valid_read_pos = 0; // buffer_size-1;
	
	if ( !(buffer = (OMSBuffer *)malloc(sizeof(OMSBuffer))) ) {
		munmap(slots, control->nslots*sizeof(OMSSlot));
		munmap(control, sizeof(OMSControl));
		return NULL;
	}

	buffer->type = buff_shm;
	buffer->slots = slots;
	buffer->known_slots = control->nslots;
	strncpy(buffer->filename, shm_name, sizeof(buffer->filename)-1);
	// buffer->fd = -1;
	// buffer->fd = NULL;
	buffer->slots = slots;
	buffer->control = control;
	
	pthread_mutex_unlock(&control->syn);
	
	return buffer;
}