linuxthreads/semaphore.h

   1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
   2 /* threads for Linux.                                                   */
   3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
   4 /*                                                                      */
   5 /* This program is free software; you can redistribute it and/or        */
   6 /* modify it under the terms of the GNU Library General Public License  */
   7 /* as published by the Free Software Foundation; either version 2       */
   8 /* of the License, or (at your option) any later version.               */
   9 /*                                                                      */
  10 /* This program is distributed in the hope that it will be useful,      */
  11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
  12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
  13 /* GNU Library General Public License for more details.                 */
  14
  15 #ifndef _SEMAPHORE_H
  16 #define _SEMAPHORE_H    1
  17
  18 #include <features.h>
  19 #include <sys/types.h>
  20
  21 #ifndef _PTHREAD_DESCR_DEFINED
  22 /* Thread descriptors.  Needed for `sem_t' definition.  */
  23 typedef struct _pthread_descr_struct *_pthread_descr;
  24 # define _PTHREAD_DESCR_DEFINED
  25 #endif
  26
  27 /* System specific semaphore definition.  */
  28 typedef struct
  29 {
  30   struct
  31   {
  32     long int status;
  33     int spinlock;
  34   } __sem_lock;
  35   int __sem_value;
  36   _pthread_descr __sem_waiting;
  37 } sem_t;
  38
  39
  40
  41 /* Value returned if `sem_open' failed.  */
  42 #define SEM_FAILED      ((sem_t *) NULL)
  43
  44 /* Maximum value the semaphore can have.  */
  45 #define SEM_VALUE_MAX   ((int) ((~0u) >> 1))
  46
  47
  48 __BEGIN_DECLS
  49
  50 /* Initialize semaphore object SEM to VALUE.  If PSHARED then share it
  51    with other processes.  */
  52 extern int sem_init (sem_t *__sem, int __pshared, unsigned int __value) __THROW;
  53
  54 /* Free resources associated with semaphore object SEM.  */
  55 extern int sem_destroy (sem_t *__sem) __THROW;
  56
  57 /* Open a named semaphore NAME with open flaot OFLAG.  */
  58 extern sem_t *sem_open (__const char *__name, int __oflag, ...) __THROW;
  59
  60 /* Close descriptor for named semaphore SEM.  */
  61 extern int sem_close (sem_t *__sem) __THROW;
  62
  63 /* Remove named semaphore NAME.  */
  64 extern int sem_unlink (__const char *__name) __THROW;
  65
  66 /* Wait for SEM being posted.  */
  67 extern int sem_wait (sem_t *__sem) __THROW;
  68
  69 /* Test whether SEM is posted.  */
  70 extern int sem_trywait (sem_t *__sem) __THROW;
  71
  72 /* Post SEM.  */
  73 extern int sem_post (sem_t *__sem) __THROW;
  74
  75 /* Get current value of SEM and store it in *SVAL.  */
  76 extern int sem_getvalue (sem_t *__sem, int *__sval) __THROW;
  77
  78 __END_DECLS
  79
  80 #endif  /* semaphore.h */