src/liboggplay/os2_semaphore.c

   1 /* ***** BEGIN LICENSE BLOCK *****
   2  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   3  *
   4  * The contents of this file are subject to the Mozilla Public License Version
   5  * 1.1 (the "License"); you may not use this file except in compliance with
   6  * the License. You may obtain a copy of the License at
   7  * http://www.mozilla.org/MPL/
   8  *
   9  * Software distributed under the License is distributed on an "AS IS" basis,
  10  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  11  * for the specific language governing rights and limitations under the
  12  * License.
  13  *
  14  * The Original Code is the Mozilla browser.
  15  *
  16  * The Initial Developer of the Original Code is
  17  * Richard Walsh
  18  * Portions created by the Initial Developer are Copyright (c) 2008
  19  * the Initial Developer. All Rights Reserved.
  20  *
  21  * Contributor(s):
  22  *
  23  * Alternatively, the contents of this file may be used under the terms of
  24  * either the GNU General Public License Version 2 or later (the "GPL"), or
  25  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  26  * in which case the provisions of the GPL or the LGPL are applicable instead
  27  * of those above. If you wish to allow use of your version of this file only
  28  * under the terms of either the GPL or the LGPL, and not to allow others to
  29  * use your version of this file under the terms of the MPL, indicate your
  30  * decision by deleting the provisions above and replace them with the notice
  31  * and other provisions required by the GPL or the LGPL. If you do not delete
  32  * the provisions above, a recipient may use your version of this file under
  33  * the terms of any one of the MPL, the GPL or the LGPL.
  34  *
  35  * ***** END LICENSE BLOCK ***** *
  36  */
  37 /*****************************************************************************/
  38 /*
  39  *  This is a conservative implementation of a posix counting semaphore.
  40  *  It relies on the state of the underlying OS/2 event semaphore to
  41  *  control whether sem_wait() blocks or returns immediately, and only
  42  *  uses its count to change the sem's state from posted to reset.
  43  *  (A more "activist" approach would use the count to decide whether
  44  *  to return immediately or to call DosWaitEventSem().)
  45  *
  46  */
  47 /*****************************************************************************/
  48
  49 #include <stdlib.h>
  50 #define INCL_DOS
  51 #include <os2.h>
  52 #include "os2_semaphore.h"
  53
  54 #ifndef ERROR_SEM_BUSY
  55 #define ERROR_SEM_BUSY  301
  56 #endif
  57
  58 #define SEM_WAIT        20000
  59
  60 /*****************************************************************************/
  61
  62 int sem_init(sem_t *sem, int pshared, unsigned value)
  63 {
  64   OS2SEM *    psem;
  65
  66   if (!sem)
  67     return -1;
  68   *sem = 0;
  69
  70   psem = (OS2SEM*)malloc(sizeof(OS2SEM));
  71   if (!psem)
  72     return -1;
  73
  74   if (DosCreateMutexSem(0, &psem->hmtx, 0, 0)) {
  75     free(psem);
  76     return -1;
  77   }
  78
  79   if (DosCreateEventSem(0, &psem->hev, 0, (value ? 1 : 0))) {
  80     DosCloseMutexSem(psem->hmtx);
  81     free(psem);
  82     return -1;
  83   }
  84
  85   psem->cnt = value;
  86   *sem = psem;
  87   return 0;
  88 }
  89
  90 /*****************************************************************************/
  91
  92 int sem_wait(sem_t *sem)
  93 {
  94   OS2SEM *    psem;
  95   ULONG       cnt;
  96
  97   if (!sem || !*sem)
  98     return -1;
  99   psem = *sem;
 100
 101   if (DosWaitEventSem(psem->hev, -1))
 102     return -1;
 103
 104   if (DosRequestMutexSem(psem->hmtx, SEM_WAIT))
 105     return -1;
 106
 107   if (psem->cnt)
 108     psem->cnt--;
 109   if (!psem->cnt)
 110     DosResetEventSem(psem->hev, &cnt);
 111   DosReleaseMutexSem(psem->hmtx);
 112
 113   return 0;
 114 }
 115
 116 /*****************************************************************************/
 117
 118 int sem_post(sem_t *sem)
 119 {
 120   OS2SEM *    psem;
 121
 122   if (!sem || !*sem)
 123     return -1;
 124   psem = *sem;
 125
 126   if (!DosRequestMutexSem(psem->hmtx, SEM_WAIT)) {
 127     psem->cnt++;
 128     DosPostEventSem(psem->hev);
 129     DosReleaseMutexSem(psem->hmtx);
 130     return 0;
 131   }
 132
 133   return -1;
 134 }
 135
 136 /*****************************************************************************/
 137
 138 int sem_destroy(sem_t *sem)
 139 {
 140   OS2SEM *    psem;
 141
 142   if (!sem || !*sem)
 143     return -1;
 144   psem = *sem;
 145
 146   if (DosCloseMutexSem(psem->hmtx) == ERROR_SEM_BUSY) {
 147     DosRequestMutexSem(psem->hmtx, SEM_WAIT);
 148     DosReleaseMutexSem(psem->hmtx);
 149     DosCloseMutexSem(psem->hmtx);
 150   }
 151
 152   if (DosCloseEventSem(psem->hev) == ERROR_SEM_BUSY) {
 153     DosPostEventSem(psem->hev);
 154     DosSleep(1);
 155     DosCloseEventSem(psem->hev);
 156   }
 157
 158   free(psem);
 159   return 0;
 160 }
 161
 162 /*****************************************************************************/
 163