semaphore.c

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00001 /*
00002  * Copyright (C) 2000-2004 by ETH Zurich
00003  *
00004  * Redistribution and use in source and binary forms, with or without
00005  * modification, are permitted provided that the following conditions
00006  * are met:
00007  *
00008  * 1. Redistributions of source code must retain the above copyright
00009  *    notice, this list of conditions and the following disclaimer.
00010  * 2. Redistributions in binary form must reproduce the above copyright
00011  *    notice, this list of conditions and the following disclaimer in the
00012  *    documentation and/or other materials provided with the distribution.
00013  * 3. Neither the name of the copyright holders nor the names of
00014  *    contributors may be used to endorse or promote products derived
00015  *    from this software without specific prior written permission.
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY ETH ZURICH AND CONTRIBUTORS
00018  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00019  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00020  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ETH ZURICH
00021  * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00022  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00023  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
00024  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
00025  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
00026  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
00027  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00028  * SUCH DAMAGE.
00029  *
00030  * For additional information see http://www.ethernut.de/
00031  *
00032  */
00033 
00034 /* semaphore.c - a nut/os implementation of semaphore functions
00035  *
00036  * 2004.05.06 Matthias Ringwald <matthias.ringwald@inf.ethz.ch>
00037  *
00038  */
00039 /*
00040  * $Log: semaphore.c,v $
00041  * Revision 1.7  2006/10/08 16:48:22  haraldkipp
00042  * Documentation fixed
00043  *
00044  * Revision 1.6  2005/08/02 17:47:04  haraldkipp
00045  * Major API documentation update.
00046  *
00047  * Revision 1.5  2004/06/03 08:44:50  olereinhardt
00048  * According to a hint from oliver I changed NutEventWait to NutEventWaitNext
00049  *
00050  * Revision 1.4  2004/06/03 08:24:21  olereinhardt
00051  * Changed semaphore behavior in NutSemTryWait too.
00052  *
00053  * Revision 1.3  2004/06/02 16:42:53  olereinhardt
00054  * fixed bug (integer overflow) in semaphore implementation.
00055  *
00056  * Revision 1.2  2004/05/18 18:38:42  drsung
00057  * Added $Log keyword for CVS.
00058  *
00059  */
00060 
00065 
00066 #ifdef __cplusplus
00067 extern "C" {
00068 #endif
00069 
00070 #include <sys/semaphore.h>
00071 #include <sys/event.h>
00072 
00076     void NutSemInit(SEM * sem, short value) {
00077         sem->qhp = 0;
00078         sem->value = value;
00079     } void NutSemWait(SEM * sem) {
00088         sem->value--;
00089         if (sem->value < 0)
00090         {
00091             NutEventWaitNext(&sem->qhp, NUT_WAIT_INFINITE);
00092         }
00093     }
00094 
00100     void NutSemPost(SEM * sem) {
00101         sem->value++;
00102         if (sem->value <= 0)
00103         {
00104             NutEventPost(&sem->qhp);
00105         }
00106     }
00107 
00115     int NutSemTryWait(SEM * sem) {
00116         if (sem->value < 0)
00117             return -1;
00118         else
00119             NutSemWait(sem);
00120         return 0;
00121     }
00122 
00130     int NutSemDestroy(SEM * sem) {
00131         if (sem->qhp == SIGNALED)
00132             return 0;
00133         if (sem->qhp == 0)
00134             return 0;
00135         return -1;
00136     }
00137 
00138 #ifdef __cplusplus
00139 }
00140 #endif
00141 

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