Mercurial > sdl-ios-xcode
annotate src/thread/generic/SDL_syscond.c @ 1358:c71e05b4dc2e
More header massaging... works great on Windows. ;-)
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Fri, 10 Feb 2006 06:48:43 +0000 |
| parents | 604d73db6802 |
| children | d910939febfa |
| rev | line source |
|---|---|
| 0 | 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 |
| 0 | 4 |
| 5 This library is free software; you can redistribute it and/or | |
|
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parents:
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6 modify it under the terms of the GNU Lesser General Public |
| 0 | 7 License as published by the Free Software Foundation; either |
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Sam Lantinga <slouken@libsdl.org>
parents:
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8 version 2.1 of the License, or (at your option) any later version. |
| 0 | 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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Sam Lantinga <slouken@libsdl.org>
parents:
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diff
changeset
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13 Lesser General Public License for more details. |
| 0 | 14 |
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Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
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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:
769
diff
changeset
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16 License along with this library; if not, write to the Free Software |
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c9b51268668f
Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
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17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 0 | 18 |
| 19 Sam Lantinga | |
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20 slouken@libsdl.org |
| 0 | 21 */ |
| 22 | |
| 23 /* An implementation of condition variables using semaphores and mutexes */ | |
| 24 /* | |
| 25 This implementation borrows heavily from the BeOS condition variable | |
| 26 implementation, written by Christopher Tate and Owen Smith. Thanks! | |
| 27 */ | |
| 28 | |
| 29 #include "SDL_thread.h" | |
| 30 | |
| 31 struct SDL_cond | |
| 32 { | |
| 33 SDL_mutex *lock; | |
| 34 int waiting; | |
| 35 int signals; | |
| 36 SDL_sem *wait_sem; | |
| 37 SDL_sem *wait_done; | |
| 38 }; | |
| 39 | |
| 40 /* Create a condition variable */ | |
| 41 SDL_cond * SDL_CreateCond(void) | |
| 42 { | |
| 43 SDL_cond *cond; | |
| 44 | |
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45 cond = (SDL_cond *) SDL_malloc(sizeof(SDL_cond)); |
| 0 | 46 if ( cond ) { |
| 47 cond->lock = SDL_CreateMutex(); | |
| 48 cond->wait_sem = SDL_CreateSemaphore(0); | |
| 49 cond->wait_done = SDL_CreateSemaphore(0); | |
| 50 cond->waiting = cond->signals = 0; | |
| 51 if ( ! cond->lock || ! cond->wait_sem || ! cond->wait_done ) { | |
| 52 SDL_DestroyCond(cond); | |
| 53 cond = NULL; | |
| 54 } | |
| 55 } else { | |
| 56 SDL_OutOfMemory(); | |
| 57 } | |
| 58 return(cond); | |
| 59 } | |
| 60 | |
| 61 /* Destroy a condition variable */ | |
| 62 void SDL_DestroyCond(SDL_cond *cond) | |
| 63 { | |
| 64 if ( cond ) { | |
| 65 if ( cond->wait_sem ) { | |
| 66 SDL_DestroySemaphore(cond->wait_sem); | |
| 67 } | |
| 68 if ( cond->wait_done ) { | |
| 69 SDL_DestroySemaphore(cond->wait_done); | |
| 70 } | |
| 71 if ( cond->lock ) { | |
| 72 SDL_DestroyMutex(cond->lock); | |
| 73 } | |
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Sam Lantinga <slouken@libsdl.org>
parents:
1330
diff
changeset
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74 SDL_free(cond); |
| 0 | 75 } |
| 76 } | |
| 77 | |
| 78 /* Restart one of the threads that are waiting on the condition variable */ | |
| 79 int SDL_CondSignal(SDL_cond *cond) | |
| 80 { | |
| 81 if ( ! cond ) { | |
| 82 SDL_SetError("Passed a NULL condition variable"); | |
| 83 return -1; | |
| 84 } | |
| 85 | |
| 86 /* If there are waiting threads not already signalled, then | |
| 87 signal the condition and wait for the thread to respond. | |
| 88 */ | |
| 89 SDL_LockMutex(cond->lock); | |
| 90 if ( cond->waiting > cond->signals ) { | |
| 91 ++cond->signals; | |
| 92 SDL_SemPost(cond->wait_sem); | |
| 93 SDL_UnlockMutex(cond->lock); | |
| 94 SDL_SemWait(cond->wait_done); | |
| 95 } else { | |
| 96 SDL_UnlockMutex(cond->lock); | |
| 97 } | |
| 98 | |
| 99 return 0; | |
| 100 } | |
| 101 | |
| 102 /* Restart all threads that are waiting on the condition variable */ | |
| 103 int SDL_CondBroadcast(SDL_cond *cond) | |
| 104 { | |
| 105 if ( ! cond ) { | |
| 106 SDL_SetError("Passed a NULL condition variable"); | |
| 107 return -1; | |
| 108 } | |
| 109 | |
| 110 /* If there are waiting threads not already signalled, then | |
| 111 signal the condition and wait for the thread to respond. | |
| 112 */ | |
| 113 SDL_LockMutex(cond->lock); | |
| 114 if ( cond->waiting > cond->signals ) { | |
| 115 int i, num_waiting; | |
| 116 | |
| 117 num_waiting = (cond->waiting - cond->signals); | |
| 118 cond->signals = cond->waiting; | |
| 119 for ( i=0; i<num_waiting; ++i ) { | |
| 120 SDL_SemPost(cond->wait_sem); | |
| 121 } | |
| 122 /* Now all released threads are blocked here, waiting for us. | |
| 123 Collect them all (and win fabulous prizes!) :-) | |
| 124 */ | |
| 125 SDL_UnlockMutex(cond->lock); | |
| 126 for ( i=0; i<num_waiting; ++i ) { | |
| 127 SDL_SemWait(cond->wait_done); | |
| 128 } | |
| 129 } else { | |
| 130 SDL_UnlockMutex(cond->lock); | |
| 131 } | |
| 132 | |
| 133 return 0; | |
| 134 } | |
| 135 | |
| 136 /* Wait on the condition variable for at most 'ms' milliseconds. | |
| 137 The mutex must be locked before entering this function! | |
| 138 The mutex is unlocked during the wait, and locked again after the wait. | |
| 139 | |
| 140 Typical use: | |
| 141 | |
| 142 Thread A: | |
| 143 SDL_LockMutex(lock); | |
| 144 while ( ! condition ) { | |
| 145 SDL_CondWait(cond); | |
| 146 } | |
| 147 SDL_UnlockMutex(lock); | |
| 148 | |
| 149 Thread B: | |
| 150 SDL_LockMutex(lock); | |
| 151 ... | |
| 152 condition = true; | |
| 153 ... | |
| 154 SDL_UnlockMutex(lock); | |
| 155 */ | |
| 156 int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms) | |
| 157 { | |
| 158 int retval; | |
| 159 | |
| 160 if ( ! cond ) { | |
| 161 SDL_SetError("Passed a NULL condition variable"); | |
| 162 return -1; | |
| 163 } | |
| 164 | |
| 165 /* Obtain the protection mutex, and increment the number of waiters. | |
| 166 This allows the signal mechanism to only perform a signal if there | |
| 167 are waiting threads. | |
| 168 */ | |
| 169 SDL_LockMutex(cond->lock); | |
| 170 ++cond->waiting; | |
| 171 SDL_UnlockMutex(cond->lock); | |
| 172 | |
| 173 /* Unlock the mutex, as is required by condition variable semantics */ | |
| 174 SDL_UnlockMutex(mutex); | |
| 175 | |
| 176 /* Wait for a signal */ | |
| 177 if ( ms == SDL_MUTEX_MAXWAIT ) { | |
| 178 retval = SDL_SemWait(cond->wait_sem); | |
| 179 } else { | |
| 180 retval = SDL_SemWaitTimeout(cond->wait_sem, ms); | |
| 181 } | |
| 182 | |
| 183 /* Let the signaler know we have completed the wait, otherwise | |
| 184 the signaler can race ahead and get the condition semaphore | |
| 185 if we are stopped between the mutex unlock and semaphore wait, | |
| 186 giving a deadlock. See the following URL for details: | |
| 187 http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html | |
| 188 */ | |
| 189 SDL_LockMutex(cond->lock); | |
| 190 if ( cond->signals > 0 ) { | |
| 191 /* If we timed out, we need to eat a condition signal */ | |
| 192 if ( retval > 0 ) { | |
| 193 SDL_SemWait(cond->wait_sem); | |
| 194 } | |
| 195 /* We always notify the signal thread that we are done */ | |
| 196 SDL_SemPost(cond->wait_done); | |
| 197 | |
| 198 /* Signal handshake complete */ | |
| 199 --cond->signals; | |
| 200 } | |
| 201 --cond->waiting; | |
| 202 SDL_UnlockMutex(cond->lock); | |
| 203 | |
| 204 /* Lock the mutex, as is required by condition variable semantics */ | |
| 205 SDL_LockMutex(mutex); | |
| 206 | |
| 207 return retval; | |
| 208 } | |
| 209 | |
| 210 /* Wait on the condition variable forever */ | |
| 211 int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex) | |
| 212 { | |
| 213 return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); | |
| 214 } |