| 1 | /* |
| 2 | SDL - Simple DirectMedia Layer |
| 3 | Copyright (C) 1997-2009 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@libsdl.org |
| 21 | */ |
| 22 | #include "SDL_config.h" |
| 23 | |
| 24 | /* An implementation of semaphores using mutexes and condition variables */ |
| 25 | |
| 26 | #include "SDL_timer.h" |
| 27 | #include "SDL_thread.h" |
| 28 | #include "SDL_systhread_c.h" |
| 29 | |
| 30 | |
| 31 | #if SDL_THREADS_DISABLED |
| 32 | |
| 33 | SDL_sem *SDL_CreateSemaphore(Uint32 initial_value) |
| 34 | { |
| 35 | SDL_SetError("SDL not configured with thread support"); |
| 36 | return (SDL_sem *)0; |
| 37 | } |
| 38 | |
| 39 | void SDL_DestroySemaphore(SDL_sem *sem) |
| 40 | { |
| 41 | return; |
| 42 | } |
| 43 | |
| 44 | int SDL_SemTryWait(SDL_sem *sem) |
| 45 | { |
| 46 | SDL_SetError("SDL not configured with thread support"); |
| 47 | return -1; |
| 48 | } |
| 49 | |
| 50 | int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout) |
| 51 | { |
| 52 | SDL_SetError("SDL not configured with thread support"); |
| 53 | return -1; |
| 54 | } |
| 55 | |
| 56 | int SDL_SemWait(SDL_sem *sem) |
| 57 | { |
| 58 | SDL_SetError("SDL not configured with thread support"); |
| 59 | return -1; |
| 60 | } |
| 61 | |
| 62 | Uint32 SDL_SemValue(SDL_sem *sem) |
| 63 | { |
| 64 | return 0; |
| 65 | } |
| 66 | |
| 67 | int SDL_SemPost(SDL_sem *sem) |
| 68 | { |
| 69 | SDL_SetError("SDL not configured with thread support"); |
| 70 | return -1; |
| 71 | } |
| 72 | |
| 73 | #else |
| 74 | |
| 75 | struct SDL_semaphore |
| 76 | { |
| 77 | Uint32 count; |
| 78 | Uint32 waiters_count; |
| 79 | SDL_mutex *count_lock; |
| 80 | SDL_cond *count_nonzero; |
| 81 | }; |
| 82 | |
| 83 | SDL_sem *SDL_CreateSemaphore(Uint32 initial_value) |
| 84 | { |
| 85 | SDL_sem *sem; |
| 86 | |
| 87 | sem = (SDL_sem *)SDL_malloc(sizeof(*sem)); |
| 88 | if ( ! sem ) { |
| 89 | SDL_OutOfMemory(); |
| 90 | return NULL; |
| 91 | } |
| 92 | sem->count = initial_value; |
| 93 | sem->waiters_count = 0; |
| 94 | |
| 95 | sem->count_lock = SDL_CreateMutex(); |
| 96 | sem->count_nonzero = SDL_CreateCond(); |
| 97 | if ( ! sem->count_lock || ! sem->count_nonzero ) { |
| 98 | SDL_DestroySemaphore(sem); |
| 99 | return NULL; |
| 100 | } |
| 101 | |
| 102 | return sem; |
| 103 | } |
| 104 | |
| 105 | /* WARNING: |
| 106 | You cannot call this function when another thread is using the semaphore. |
| 107 | */ |
| 108 | void SDL_DestroySemaphore(SDL_sem *sem) |
| 109 | { |
| 110 | if ( sem ) { |
| 111 | sem->count = 0xFFFFFFFF; |
| 112 | while ( sem->waiters_count > 0) { |
| 113 | SDL_CondSignal(sem->count_nonzero); |
| 114 | SDL_Delay(10); |
| 115 | } |
| 116 | SDL_DestroyCond(sem->count_nonzero); |
| 117 | if ( sem->count_lock ) { |
| 118 | SDL_mutexP(sem->count_lock); |
| 119 | SDL_mutexV(sem->count_lock); |
| 120 | SDL_DestroyMutex(sem->count_lock); |
| 121 | } |
| 122 | SDL_free(sem); |
| 123 | } |
| 124 | } |
| 125 | |
| 126 | int SDL_SemTryWait(SDL_sem *sem) |
| 127 | { |
| 128 | int retval; |
| 129 | |
| 130 | if ( ! sem ) { |
| 131 | SDL_SetError("Passed a NULL semaphore"); |
| 132 | return -1; |
| 133 | } |
| 134 | |
| 135 | retval = SDL_MUTEX_TIMEDOUT; |
| 136 | SDL_LockMutex(sem->count_lock); |
| 137 | if ( sem->count > 0 ) { |
| 138 | --sem->count; |
| 139 | retval = 0; |
| 140 | } |
| 141 | SDL_UnlockMutex(sem->count_lock); |
| 142 | |
| 143 | return retval; |
| 144 | } |
| 145 | |
| 146 | int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout) |
| 147 | { |
| 148 | int retval; |
| 149 | |
| 150 | if ( ! sem ) { |
| 151 | SDL_SetError("Passed a NULL semaphore"); |
| 152 | return -1; |
| 153 | } |
| 154 | |
| 155 | /* A timeout of 0 is an easy case */ |
| 156 | if ( timeout == 0 ) { |
| 157 | return SDL_SemTryWait(sem); |
| 158 | } |
| 159 | |
| 160 | SDL_LockMutex(sem->count_lock); |
| 161 | ++sem->waiters_count; |
| 162 | retval = 0; |
| 163 | while ( (sem->count == 0) && (retval != SDL_MUTEX_TIMEDOUT) ) { |
| 164 | retval = SDL_CondWaitTimeout(sem->count_nonzero, |
| 165 | sem->count_lock, timeout); |
| 166 | } |
| 167 | --sem->waiters_count; |
| 168 | if (retval == 0) { |
| 169 | --sem->count; |
| 170 | } |
| 171 | SDL_UnlockMutex(sem->count_lock); |
| 172 | |
| 173 | return retval; |
| 174 | } |
| 175 | |
| 176 | int SDL_SemWait(SDL_sem *sem) |
| 177 | { |
| 178 | return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT); |
| 179 | } |
| 180 | |
| 181 | Uint32 SDL_SemValue(SDL_sem *sem) |
| 182 | { |
| 183 | Uint32 value; |
| 184 | |
| 185 | value = 0; |
| 186 | if ( sem ) { |
| 187 | SDL_LockMutex(sem->count_lock); |
| 188 | value = sem->count; |
| 189 | SDL_UnlockMutex(sem->count_lock); |
| 190 | } |
| 191 | return value; |
| 192 | } |
| 193 | |
| 194 | int SDL_SemPost(SDL_sem *sem) |
| 195 | { |
| 196 | if ( ! sem ) { |
| 197 | SDL_SetError("Passed a NULL semaphore"); |
| 198 | return -1; |
| 199 | } |
| 200 | |
| 201 | SDL_LockMutex(sem->count_lock); |
| 202 | if ( sem->waiters_count > 0 ) { |
| 203 | SDL_CondSignal(sem->count_nonzero); |
| 204 | } |
| 205 | ++sem->count; |
| 206 | SDL_UnlockMutex(sem->count_lock); |
| 207 | |
| 208 | return 0; |
| 209 | } |
| 210 | |
| 211 | #endif /* SDL_THREADS_DISABLED */ |