1 /* 2 SDL - Simple DirectMedia Layer 3 Copyright (C) 1997-2012 Sam Lantinga 4 5 This library is free software; you can redistribute it and/or 6 modify it under the terms of the GNU Lesser General Public 7 License as published by the Free Software Foundation; either 8 version 2.1 of the License, or (at your option) any later version. 9 10 This library 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 GNU 13 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public 16 License along with this library; if not, write to the Free Software 17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 18 19 Sam Lantinga 20 slouken (at) libsdl.org 21 */ 22 #include "SDL_config.h" 23 24 #include <pthread.h> 25 #include <semaphore.h> 26 #include <errno.h> 27 #include <sys/time.h> 28 29 #include "SDL_thread.h" 30 #include "SDL_timer.h" 31 32 /* Wrapper around POSIX 1003.1b semaphores */ 33 34 #ifdef __MACOSX__ 35 /* Mac OS X doesn't support sem_getvalue() as of version 10.4 */ 36 #include "../generic/SDL_syssem.c" 37 #else 38 39 struct SDL_semaphore { 40 sem_t sem; 41 }; 42 43 /* Create a semaphore, initialized with value */ 44 SDL_sem *SDL_CreateSemaphore(Uint32 initial_value) 45 { 46 SDL_sem *sem = (SDL_sem *) SDL_malloc(sizeof(SDL_sem)); 47 if ( sem ) { 48 if ( sem_init(&sem->sem, 0, initial_value) < 0 ) { 49 SDL_SetError("sem_init() failed"); 50 SDL_free(sem); 51 sem = NULL; 52 } 53 } else { 54 SDL_OutOfMemory(); 55 } 56 return sem; 57 } 58 59 void SDL_DestroySemaphore(SDL_sem *sem) 60 { 61 if ( sem ) { 62 sem_destroy(&sem->sem); 63 SDL_free(sem); 64 } 65 } 66 67 int SDL_SemTryWait(SDL_sem *sem) 68 { 69 int retval; 70 71 if ( ! sem ) { 72 SDL_SetError("Passed a NULL semaphore"); 73 return -1; 74 } 75 retval = SDL_MUTEX_TIMEDOUT; 76 if ( sem_trywait(&sem->sem) == 0 ) { 77 retval = 0; 78 } 79 return retval; 80 } 81 82 int SDL_SemWait(SDL_sem *sem) 83 { 84 int retval; 85 86 if ( ! sem ) { 87 SDL_SetError("Passed a NULL semaphore"); 88 return -1; 89 } 90 91 while ( ((retval = sem_wait(&sem->sem)) == -1) && (errno == EINTR) ) {} 92 if ( retval < 0 ) { 93 SDL_SetError("sem_wait() failed"); 94 } 95 return retval; 96 } 97 98 int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout) 99 { 100 int retval; 101 #ifdef HAVE_SEM_TIMEDWAIT 102 struct timeval now; 103 struct timespec ts_timeout; 104 #else 105 Uint32 end; 106 #endif 107 108 if ( ! sem ) { 109 SDL_SetError("Passed a NULL semaphore"); 110 return -1; 111 } 112 113 /* Try the easy cases first */ 114 if ( timeout == 0 ) { 115 return SDL_SemTryWait(sem); 116 } 117 if ( timeout == SDL_MUTEX_MAXWAIT ) { 118 return SDL_SemWait(sem); 119 } 120 121 #ifdef HAVE_SEM_TIMEDWAIT 122 /* Setup the timeout. sem_timedwait doesn't wait for 123 * a lapse of time, but until we reach a certain time. 124 * This time is now plus the timeout. 125 */ 126 gettimeofday(&now, NULL); 127 128 /* Add our timeout to current time */ 129 now.tv_usec += (timeout % 1000) * 1000; 130 now.tv_sec += timeout / 1000; 131 132 /* Wrap the second if needed */ 133 if ( now.tv_usec >= 1000000 ) { 134 now.tv_usec -= 1000000; 135 now.tv_sec ++; 136 } 137 138 /* Convert to timespec */ 139 ts_timeout.tv_sec = now.tv_sec; 140 ts_timeout.tv_nsec = now.tv_usec * 1000; 141 142 /* Wait. */ 143 do 144 retval = sem_timedwait(&sem->sem, &ts_timeout); 145 while (retval == -1 && errno == EINTR); 146 147 if (retval == -1) 148 SDL_SetError(strerror(errno)); 149 #else 150 end = SDL_GetTicks() + timeout; 151 while ((retval = SDL_SemTryWait(sem)) == SDL_MUTEX_TIMEDOUT) { 152 if ((SDL_GetTicks() - end) >= 0) { 153 break; 154 } 155 SDL_Delay(0); 156 } 157 #endif /* HAVE_SEM_TIMEDWAIT */ 158 159 return retval; 160 } 161 162 Uint32 SDL_SemValue(SDL_sem *sem) 163 { 164 int ret = 0; 165 if ( sem ) { 166 sem_getvalue(&sem->sem, &ret); 167 if ( ret < 0 ) { 168 ret = 0; 169 } 170 } 171 return (Uint32)ret; 172 } 173 174 int SDL_SemPost(SDL_sem *sem) 175 { 176 int retval; 177 178 if ( ! sem ) { 179 SDL_SetError("Passed a NULL semaphore"); 180 return -1; 181 } 182 183 retval = sem_post(&sem->sem); 184 if ( retval < 0 ) { 185 SDL_SetError("sem_post() failed"); 186 } 187 return retval; 188 } 189 190 #endif /* __MACOSX__ */ 191
