Mercurial > sdl-ios-xcode
annotate src/thread/os2/SDL_syscond.c @ 1650:ee4f2d77206f
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| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sat, 22 Apr 2006 19:50:23 +0000 |
| parents | d910939febfa |
| children | 782fd950bd46 c121d94672cb a1b03ba2fcd0 |
| rev | line source |
|---|---|
| 1190 | 1 /* |
| 2 SDL - Simple DirectMedia Layer | |
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Sam Lantinga <slouken@libsdl.org>
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3 Copyright (C) 1997-2006 Sam Lantinga |
| 1190 | 4 |
| 5 This library is free software; you can redistribute it and/or | |
|
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6 modify it under the terms of the GNU Lesser General Public |
| 1190 | 7 License as published by the Free Software Foundation; either |
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8 version 2.1 of the License, or (at your option) any later version. |
| 1190 | 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 | |
|
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13 Lesser General Public License for more details. |
| 1190 | 14 |
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1312
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Sam Lantinga <slouken@libsdl.org>
parents:
1190
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15 You should have received a copy of the GNU Lesser General Public |
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c9b51268668f
Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
1190
diff
changeset
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16 License along with this library; if not, write to the Free Software |
|
c9b51268668f
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Sam Lantinga <slouken@libsdl.org>
parents:
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diff
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17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 1190 | 18 |
| 19 Sam Lantinga | |
| 20 slouken@libsdl.org | |
| 21 */ | |
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22 #include "SDL_config.h" |
| 1190 | 23 |
| 24 /* An implementation of condition variables using semaphores and mutexes */ | |
| 25 /* | |
| 26 This implementation borrows heavily from the BeOS condition variable | |
| 27 implementation, written by Christopher Tate and Owen Smith. Thanks! | |
| 28 */ | |
| 29 | |
| 30 #include "SDL_thread.h" | |
| 31 | |
| 32 struct SDL_cond | |
| 33 { | |
| 34 SDL_mutex *lock; | |
| 35 int waiting; | |
| 36 int signals; | |
| 37 SDL_sem *wait_sem; | |
| 38 SDL_sem *wait_done; | |
| 39 }; | |
| 40 | |
| 41 /* Create a condition variable */ | |
| 42 DECLSPEC SDL_cond * SDLCALL SDL_CreateCond(void) | |
| 43 { | |
| 44 SDL_cond *cond; | |
| 45 | |
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46 cond = (SDL_cond *) SDL_malloc(sizeof(SDL_cond)); |
| 1190 | 47 if ( cond ) { |
| 48 cond->lock = SDL_CreateMutex(); | |
| 49 cond->wait_sem = SDL_CreateSemaphore(0); | |
| 50 cond->wait_done = SDL_CreateSemaphore(0); | |
| 51 cond->waiting = cond->signals = 0; | |
| 52 if ( ! cond->lock || ! cond->wait_sem || ! cond->wait_done ) { | |
| 53 SDL_DestroyCond(cond); | |
| 54 cond = NULL; | |
| 55 } | |
| 56 } else { | |
| 57 SDL_OutOfMemory(); | |
| 58 } | |
| 59 return(cond); | |
| 60 } | |
| 61 | |
| 62 /* Destroy a condition variable */ | |
| 63 DECLSPEC void SDLCALL SDL_DestroyCond(SDL_cond *cond) | |
| 64 { | |
| 65 if ( cond ) { | |
| 66 if ( cond->wait_sem ) { | |
| 67 SDL_DestroySemaphore(cond->wait_sem); | |
| 68 } | |
| 69 if ( cond->wait_done ) { | |
| 70 SDL_DestroySemaphore(cond->wait_done); | |
| 71 } | |
| 72 if ( cond->lock ) { | |
| 73 SDL_DestroyMutex(cond->lock); | |
| 74 } | |
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75 SDL_free(cond); |
| 1190 | 76 } |
| 77 } | |
| 78 | |
| 79 /* Restart one of the threads that are waiting on the condition variable */ | |
| 80 DECLSPEC int SDLCALL SDL_CondSignal(SDL_cond *cond) | |
| 81 { | |
| 82 if ( ! cond ) { | |
| 83 SDL_SetError("Passed a NULL condition variable"); | |
| 84 return -1; | |
| 85 } | |
| 86 | |
| 87 /* If there are waiting threads not already signalled, then | |
| 88 signal the condition and wait for the thread to respond. | |
| 89 */ | |
| 90 SDL_LockMutex(cond->lock); | |
| 91 if ( cond->waiting > cond->signals ) { | |
| 92 ++cond->signals; | |
| 93 SDL_SemPost(cond->wait_sem); | |
| 94 SDL_UnlockMutex(cond->lock); | |
| 95 SDL_SemWait(cond->wait_done); | |
| 96 } else { | |
| 97 SDL_UnlockMutex(cond->lock); | |
| 98 } | |
| 99 | |
| 100 return 0; | |
| 101 } | |
| 102 | |
| 103 /* Restart all threads that are waiting on the condition variable */ | |
| 104 DECLSPEC int SDLCALL SDL_CondBroadcast(SDL_cond *cond) | |
| 105 { | |
| 106 if ( ! cond ) { | |
| 107 SDL_SetError("Passed a NULL condition variable"); | |
| 108 return -1; | |
| 109 } | |
| 110 | |
| 111 /* If there are waiting threads not already signalled, then | |
| 112 signal the condition and wait for the thread to respond. | |
| 113 */ | |
| 114 SDL_LockMutex(cond->lock); | |
| 115 if ( cond->waiting > cond->signals ) { | |
| 116 int i, num_waiting; | |
| 117 | |
| 118 num_waiting = (cond->waiting - cond->signals); | |
| 119 cond->signals = cond->waiting; | |
| 120 for ( i=0; i<num_waiting; ++i ) { | |
| 121 SDL_SemPost(cond->wait_sem); | |
| 122 } | |
| 123 /* Now all released threads are blocked here, waiting for us. | |
| 124 Collect them all (and win fabulous prizes!) :-) | |
| 125 */ | |
| 126 SDL_UnlockMutex(cond->lock); | |
| 127 for ( i=0; i<num_waiting; ++i ) { | |
| 128 SDL_SemWait(cond->wait_done); | |
| 129 } | |
| 130 } else { | |
| 131 SDL_UnlockMutex(cond->lock); | |
| 132 } | |
| 133 | |
| 134 return 0; | |
| 135 } | |
| 136 | |
| 137 /* Wait on the condition variable for at most 'ms' milliseconds. | |
| 138 The mutex must be locked before entering this function! | |
| 139 The mutex is unlocked during the wait, and locked again after the wait. | |
| 140 | |
| 141 Typical use: | |
| 142 | |
| 143 Thread A: | |
| 144 SDL_LockMutex(lock); | |
| 145 while ( ! condition ) { | |
| 146 SDL_CondWait(cond); | |
| 147 } | |
| 148 SDL_UnlockMutex(lock); | |
| 149 | |
| 150 Thread B: | |
| 151 SDL_LockMutex(lock); | |
| 152 ... | |
| 153 condition = true; | |
| 154 ... | |
| 155 SDL_UnlockMutex(lock); | |
| 156 */ | |
| 157 DECLSPEC int SDLCALL SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms) | |
| 158 { | |
| 159 int retval; | |
| 160 | |
| 161 if ( ! cond ) { | |
| 162 SDL_SetError("Passed a NULL condition variable"); | |
| 163 return -1; | |
| 164 } | |
| 165 | |
| 166 /* Obtain the protection mutex, and increment the number of waiters. | |
| 167 This allows the signal mechanism to only perform a signal if there | |
| 168 are waiting threads. | |
| 169 */ | |
| 170 SDL_LockMutex(cond->lock); | |
| 171 ++cond->waiting; | |
| 172 SDL_UnlockMutex(cond->lock); | |
| 173 | |
| 174 /* Unlock the mutex, as is required by condition variable semantics */ | |
| 175 SDL_UnlockMutex(mutex); | |
| 176 | |
| 177 /* Wait for a signal */ | |
| 178 if ( ms == SDL_MUTEX_MAXWAIT ) { | |
| 179 retval = SDL_SemWait(cond->wait_sem); | |
| 180 } else { | |
| 181 retval = SDL_SemWaitTimeout(cond->wait_sem, ms); | |
| 182 } | |
| 183 | |
| 184 /* Let the signaler know we have completed the wait, otherwise | |
| 185 the signaler can race ahead and get the condition semaphore | |
| 186 if we are stopped between the mutex unlock and semaphore wait, | |
| 187 giving a deadlock. See the following URL for details: | |
| 188 http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html | |
| 189 */ | |
| 190 SDL_LockMutex(cond->lock); | |
| 191 if ( cond->signals > 0 ) { | |
| 192 /* If we timed out, we need to eat a condition signal */ | |
| 193 if ( retval > 0 ) { | |
| 194 SDL_SemWait(cond->wait_sem); | |
| 195 } | |
| 196 /* We always notify the signal thread that we are done */ | |
| 197 SDL_SemPost(cond->wait_done); | |
| 198 | |
| 199 /* Signal handshake complete */ | |
| 200 --cond->signals; | |
| 201 } | |
| 202 --cond->waiting; | |
| 203 SDL_UnlockMutex(cond->lock); | |
| 204 | |
| 205 /* Lock the mutex, as is required by condition variable semantics */ | |
| 206 SDL_LockMutex(mutex); | |
| 207 | |
| 208 return retval; | |
| 209 } | |
| 210 | |
| 211 /* Wait on the condition variable forever */ | |
| 212 DECLSPEC int SDLCALL SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex) | |
| 213 { | |
| 214 return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); | |
| 215 } |