/**
* @file
*
* @brief Creates a new POSIX Message Queue or Opens an Existing Queue
* @ingroup POSIXAPI
*/
/*
* NOTE: The structure of the routines is identical to that of POSIX
* Message_queues to leave the option of having unnamed message
* queues at a future date. They are currently not part of the
* POSIX standard but unnamed message_queues are. This is also
* the reason for the apparently unnecessary tracking of
* the process_shared attribute. [In addition to the fact that
* it would be trivial to add pshared to the mq_attr structure
* and have process private message queues.]
*
* This code ignores the O_RDONLY/O_WRONLY/O_RDWR flag at open
* time.
*
* COPYRIGHT (c) 1989-2009.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdarg.h>
#include <pthread.h>
#include <limits.h>
#include <errno.h>
#include <fcntl.h>
#include <mqueue.h>
#include <rtems/score/todimpl.h>
#include <rtems/score/watchdog.h>
#include <rtems/posix/mqueueimpl.h>
#include <rtems/posix/time.h>
#include <rtems/seterr.h>
#define MQ_OPEN_FAILED ((mqd_t) -1)
/*
* 15.2.2 Open a Message Queue, P1003.1b-1993, p. 272
*/
mqd_t mq_open(
const char *name,
int oflag,
...
/* mode_t mode, */
/* struct mq_attr attr */
)
{
/*
* mode is set but never used. GCC gives a warning for this
* and we need to tell GCC not to complain. But we have to
* have it because we have to work through the variable
* arguments to get to attr.
*/
mode_t mode RTEMS_COMPILER_UNUSED_ATTRIBUTE;
va_list arg;
struct mq_attr *attr = NULL;
int status;
Objects_Id the_mq_id;
POSIX_Message_queue_Control *the_mq;
POSIX_Message_queue_Control_fd *the_mq_fd;
Objects_Locations location;
size_t name_len;
if ( oflag & O_CREAT ) {
va_start(arg, oflag);
mode = va_arg( arg, mode_t );
attr = va_arg( arg, struct mq_attr * );
va_end(arg);
}
the_mq_fd = _POSIX_Message_queue_Allocate_fd();
if ( !the_mq_fd ) {
_Objects_Allocator_unlock();
rtems_set_errno_and_return_value( ENFILE, MQ_OPEN_FAILED );
}
the_mq_fd->oflag = oflag;
status = _POSIX_Message_queue_Name_to_id( name, &the_mq_id, &name_len );
/*
* If the name to id translation worked, then the message queue exists
* and we can just return a pointer to the id. Otherwise we may
* need to check to see if this is a "message queue does not exist"
* or some other miscellaneous error on the name.
*/
if ( status ) {
/*
* Unless provided a valid name that did not already exist
* and we are willing to create then it is an error.
*/
if ( !( status == ENOENT && (oflag & O_CREAT) ) ) {
_POSIX_Message_queue_Free_fd( the_mq_fd );
_Objects_Allocator_unlock();
rtems_set_errno_and_return_value( status, MQ_OPEN_FAILED );
}
} else { /* name -> ID translation succeeded */
/*
* Check for existence with creation.
*/
if ( (oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL) ) {
_POSIX_Message_queue_Free_fd( the_mq_fd );
_Objects_Allocator_unlock();
rtems_set_errno_and_return_value( EEXIST, MQ_OPEN_FAILED );
}
/*
* In this case we need to do an ID->pointer conversion to
* check the mode.
*/
the_mq = _POSIX_Message_queue_Get( the_mq_id, &location );
the_mq->open_count += 1;
the_mq_fd->Queue = the_mq;
_Objects_Open_string(
&_POSIX_Message_queue_Information_fds,
&the_mq_fd->Object,
NULL
);
_Thread_Enable_dispatch();
_Objects_Allocator_unlock();
return the_mq_fd->Object.id;
}
/*
* At this point, the message queue does not exist and everything has been
* checked. We should go ahead and create a message queue.
*/
status = _POSIX_Message_queue_Create_support(
name,
name_len,
true, /* shared across processes */
attr,
&the_mq
);
/*
* errno was set by Create_support, so don't set it again.
*/
if ( status == -1 ) {
_POSIX_Message_queue_Free_fd( the_mq_fd );
_Objects_Allocator_unlock();
return MQ_OPEN_FAILED;
}
the_mq_fd->Queue = the_mq;
_Objects_Open_string(
&_POSIX_Message_queue_Information_fds,
&the_mq_fd->Object,
NULL
);
_Objects_Allocator_unlock();
return the_mq_fd->Object.id;
}