source: rtems/c/src/exec/posix/src/semopen.c @ cb3c1718

4.104.114.84.95
Last change on this file since cb3c1718 was 2545646, checked in by Jennifer Averett <Jennifer.Averett@…>, on Nov 22, 1999 at 4:12:19 PM

+ Updated comments.
+ Corrected enable/disable of dispatch.

  • Property mode set to 100644
File size: 2.7 KB
Line 
1/*
2 *  $Id$
3 */
4
5#include <stdarg.h>
6
7#include <errno.h>
8#include <fcntl.h>
9#include <pthread.h>
10#include <semaphore.h>
11#include <limits.h>
12
13#include <rtems/system.h>
14#include <rtems/score/object.h>
15#include <rtems/posix/semaphore.h>
16#include <rtems/posix/time.h>
17#include <rtems/posix/seterr.h>
18
19/*PAGE
20 *
21 *  sem_open
22 * 
23 *  Opens a named semaphore.  Used in conjunction with the sem_close
24 *  and sem_unlink commands.
25 *
26 *  11.2.3 Initialize/Open a Named Semaphore, P1003.1b-1993, p.221
27 *
28 *  NOTE: When oflag is O_CREAT, then optional third and fourth
29 *        parameters must be present.
30 */
31
32sem_t *sem_open(
33  const char *name,
34  int         oflag,
35  ...
36  /* mode_t mode, */
37  /* unsigned int value */
38)
39{
40  va_list                    arg;
41  mode_t                     mode;
42  unsigned int               value = 0;
43  int                        status;
44  Objects_Id                 the_semaphore_id;
45  POSIX_Semaphore_Control   *the_semaphore;
46  Objects_Locations          location;
47   
48  _Thread_Disable_dispatch();
49
50  if ( oflag & O_CREAT ) {
51    va_start(arg, oflag);
52    mode = va_arg( arg, mode_t );
53    value = va_arg( arg, unsigned int );
54    va_end(arg);
55  }
56
57  status = _POSIX_Semaphore_Name_to_id( name, &the_semaphore_id );
58   
59  /*
60   *  If the name to id translation worked, then the semaphore exists
61   *  and we can just return a pointer to the id.  Otherwise we may
62   *  need to check to see if this is a "semaphore does not exist"
63   *  or some other miscellaneous error on the name.
64   */
65
66  if ( status ) {
67
68    /*
69     * Unless provided a valid name that did not already exist
70     * and we are willing to create then it is an error.
71     */
72
73    if ( !( status == ENOENT && (oflag & O_CREAT) ) ) {
74      _Thread_Enable_dispatch();
75      set_errno_and_return_minus_one_cast( status, sem_t * );
76    }
77  } else { 
78
79    /*
80     * Check for existence with creation.
81     */
82
83    if ( (oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL) ) {
84      _Thread_Enable_dispatch();
85      set_errno_and_return_minus_one_cast( EEXIST, sem_t * );
86    }
87
88    the_semaphore = _POSIX_Semaphore_Get( &the_semaphore_id, &location );
89    the_semaphore->open_count += 1;
90    _Thread_Enable_dispatch();
91    _Thread_Enable_dispatch();
92    return (sem_t *)&the_semaphore->Object.id;
93
94  } 
95 
96  /*
97   *  At this point, the semaphore does not exist and everything has been
98   *  checked. We should go ahead and create a semaphore.
99   */
100
101  status =_POSIX_Semaphore_Create_support(
102    name,
103    FALSE,         /* not shared across processes */
104    value,
105    &the_semaphore
106  );
107 
108  /*
109   * errno was set by Create_support, so don't set it again.
110   */
111
112  _Thread_Enable_dispatch();
113
114  if ( status == -1 )
115    return SEM_FAILED;
116
117  return (sem_t *) &the_semaphore->Object.id;
118}
119
120
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