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