Nut/OS  4.10.3
API Reference
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  * $Log$
00041  * Revision 1.9  2009/01/17 15:37:52  haraldkipp
00042  * Added some NUTASSERT macros to check function parameters.
00043  *
00044  * Revision 1.8  2008/06/16 15:12:07  freckle
00045  * fix bug in NutSemTryWait of os/semaphore.c
00046  *
00047  * Revision 1.7  2006/10/08 16:48:22  haraldkipp
00048  * Documentation fixed
00049  *
00050  * Revision 1.6  2005/08/02 17:47:04  haraldkipp
00051  * Major API documentation update.
00052  *
00053  * Revision 1.5  2004/06/03 08:44:50  olereinhardt
00054  * According to a hint from oliver I changed NutEventWait to NutEventWaitNext
00055  *
00056  * Revision 1.4  2004/06/03 08:24:21  olereinhardt
00057  * Changed semaphore behavior in NutSemTryWait too.
00058  *
00059  * Revision 1.3  2004/06/02 16:42:53  olereinhardt
00060  * fixed bug (integer overflow) in semaphore implementation.
00061  *
00062  * Revision 1.2  2004/05/18 18:38:42  drsung
00063  * Added $Log keyword for CVS.
00064  *
00065  */
00066 
00071 
00072 #ifdef __cplusplus
00073 extern "C" {
00074 #endif
00075 
00076 #include <sys/nutdebug.h>
00077 #include <sys/semaphore.h>
00078 #include <sys/event.h>
00079 
00083     void NutSemInit(SEM * sem, short value) {
00084         NUTASSERT(sem != NULL);
00085         sem->qhp = 0;
00086         sem->value = value;
00087     } void NutSemWait(SEM * sem) {
00096         NUTASSERT(sem != NULL);
00097         sem->value--;
00098         if (sem->value < 0)
00099         {
00100             NutEventWaitNext(&sem->qhp, NUT_WAIT_INFINITE);
00101         }
00102     }
00103 
00109     void NutSemPost(SEM * sem) {
00110         NUTASSERT(sem != NULL);
00111         sem->value++;
00112         if (sem->value <= 0)
00113         {
00114             NutEventPost(&sem->qhp);
00115         }
00116     }
00117 
00125     int NutSemTryWait(SEM * sem) {
00126         NUTASSERT(sem != NULL);
00127         if (sem->value <= 0)
00128             return -1;
00129         else
00130             NutSemWait(sem);
00131         return 0;
00132     }
00133 
00141     int NutSemDestroy(SEM * sem) {
00142         NUTASSERT(sem != NULL);
00143         if (sem->qhp == SIGNALED)
00144             return 0;
00145         if (sem->qhp == 0)
00146             return 0;
00147         return -1;
00148     }
00149 
00150 #ifdef __cplusplus
00151 }
00152 #endif
00153