Mercurial > sdl-ios-xcode
annotate src/thread/generic/SDL_syscond.c @ 1330:450721ad5436
It's now possible to build SDL without any C runtime at all on Windows,
using Visual C++ 2005
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Mon, 06 Feb 2006 08:28:51 +0000 |
| parents | c9b51268668f |
| children | 3692456e7b0f |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 SDL - Simple DirectMedia Layer | |
|
1312
c9b51268668f
Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
|
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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Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
|
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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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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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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c9b51268668f
Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
|
13 Lesser General Public License for more details. |
| 0 | 14 |
|
1312
c9b51268668f
Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
|
15 You should have received a copy of the GNU Lesser General Public |
|
c9b51268668f
Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
|
16 License along with this library; if not, write to the Free Software |
|
c9b51268668f
Updated copyright information and removed rcs id lines (problematic in branch merges)
Sam Lantinga <slouken@libsdl.org>
parents:
769
diff
changeset
|
17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 0 | 18 |
| 19 Sam Lantinga | |
|
252
e8157fcb3114
Updated the source with the correct e-mail address
Sam Lantinga <slouken@libsdl.org>
parents:
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diff
changeset
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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_error.h" | |
| 30 #include "SDL_thread.h" | |
|
1330
450721ad5436
It's now possible to build SDL without any C runtime at all on Windows,
Sam Lantinga <slouken@libsdl.org>
parents:
1312
diff
changeset
|
31 #include "SDL_stdlib.h" |
| 0 | 32 |
| 33 struct SDL_cond | |
| 34 { | |
| 35 SDL_mutex *lock; | |
| 36 int waiting; | |
| 37 int signals; | |
| 38 SDL_sem *wait_sem; | |
| 39 SDL_sem *wait_done; | |
| 40 }; | |
| 41 | |
| 42 /* Create a condition variable */ | |
| 43 SDL_cond * SDL_CreateCond(void) | |
| 44 { | |
| 45 SDL_cond *cond; | |
| 46 | |
| 47 cond = (SDL_cond *) malloc(sizeof(SDL_cond)); | |
| 48 if ( cond ) { | |
| 49 cond->lock = SDL_CreateMutex(); | |
| 50 cond->wait_sem = SDL_CreateSemaphore(0); | |
| 51 cond->wait_done = SDL_CreateSemaphore(0); | |
| 52 cond->waiting = cond->signals = 0; | |
| 53 if ( ! cond->lock || ! cond->wait_sem || ! cond->wait_done ) { | |
| 54 SDL_DestroyCond(cond); | |
| 55 cond = NULL; | |
| 56 } | |
| 57 } else { | |
| 58 SDL_OutOfMemory(); | |
| 59 } | |
| 60 return(cond); | |
| 61 } | |
| 62 | |
| 63 /* Destroy a condition variable */ | |
| 64 void SDL_DestroyCond(SDL_cond *cond) | |
| 65 { | |
| 66 if ( cond ) { | |
| 67 if ( cond->wait_sem ) { | |
| 68 SDL_DestroySemaphore(cond->wait_sem); | |
| 69 } | |
| 70 if ( cond->wait_done ) { | |
| 71 SDL_DestroySemaphore(cond->wait_done); | |
| 72 } | |
| 73 if ( cond->lock ) { | |
| 74 SDL_DestroyMutex(cond->lock); | |
| 75 } | |
| 76 free(cond); | |
| 77 } | |
| 78 } | |
| 79 | |
| 80 /* Restart one of the threads that are waiting on the condition variable */ | |
| 81 int SDL_CondSignal(SDL_cond *cond) | |
| 82 { | |
| 83 if ( ! cond ) { | |
| 84 SDL_SetError("Passed a NULL condition variable"); | |
| 85 return -1; | |
| 86 } | |
| 87 | |
| 88 /* If there are waiting threads not already signalled, then | |
| 89 signal the condition and wait for the thread to respond. | |
| 90 */ | |
| 91 SDL_LockMutex(cond->lock); | |
| 92 if ( cond->waiting > cond->signals ) { | |
| 93 ++cond->signals; | |
| 94 SDL_SemPost(cond->wait_sem); | |
| 95 SDL_UnlockMutex(cond->lock); | |
| 96 SDL_SemWait(cond->wait_done); | |
| 97 } else { | |
| 98 SDL_UnlockMutex(cond->lock); | |
| 99 } | |
| 100 | |
| 101 return 0; | |
| 102 } | |
| 103 | |
| 104 /* Restart all threads that are waiting on the condition variable */ | |
| 105 int SDL_CondBroadcast(SDL_cond *cond) | |
| 106 { | |
| 107 if ( ! cond ) { | |
| 108 SDL_SetError("Passed a NULL condition variable"); | |
| 109 return -1; | |
| 110 } | |
| 111 | |
| 112 /* If there are waiting threads not already signalled, then | |
| 113 signal the condition and wait for the thread to respond. | |
| 114 */ | |
| 115 SDL_LockMutex(cond->lock); | |
| 116 if ( cond->waiting > cond->signals ) { | |
| 117 int i, num_waiting; | |
| 118 | |
| 119 num_waiting = (cond->waiting - cond->signals); | |
| 120 cond->signals = cond->waiting; | |
| 121 for ( i=0; i<num_waiting; ++i ) { | |
| 122 SDL_SemPost(cond->wait_sem); | |
| 123 } | |
| 124 /* Now all released threads are blocked here, waiting for us. | |
| 125 Collect them all (and win fabulous prizes!) :-) | |
| 126 */ | |
| 127 SDL_UnlockMutex(cond->lock); | |
| 128 for ( i=0; i<num_waiting; ++i ) { | |
| 129 SDL_SemWait(cond->wait_done); | |
| 130 } | |
| 131 } else { | |
| 132 SDL_UnlockMutex(cond->lock); | |
| 133 } | |
| 134 | |
| 135 return 0; | |
| 136 } | |
| 137 | |
| 138 /* Wait on the condition variable for at most 'ms' milliseconds. | |
| 139 The mutex must be locked before entering this function! | |
| 140 The mutex is unlocked during the wait, and locked again after the wait. | |
| 141 | |
| 142 Typical use: | |
| 143 | |
| 144 Thread A: | |
| 145 SDL_LockMutex(lock); | |
| 146 while ( ! condition ) { | |
| 147 SDL_CondWait(cond); | |
| 148 } | |
| 149 SDL_UnlockMutex(lock); | |
| 150 | |
| 151 Thread B: | |
| 152 SDL_LockMutex(lock); | |
| 153 ... | |
| 154 condition = true; | |
| 155 ... | |
| 156 SDL_UnlockMutex(lock); | |
| 157 */ | |
| 158 int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms) | |
| 159 { | |
| 160 int retval; | |
| 161 | |
| 162 if ( ! cond ) { | |
| 163 SDL_SetError("Passed a NULL condition variable"); | |
| 164 return -1; | |
| 165 } | |
| 166 | |
| 167 /* Obtain the protection mutex, and increment the number of waiters. | |
| 168 This allows the signal mechanism to only perform a signal if there | |
| 169 are waiting threads. | |
| 170 */ | |
| 171 SDL_LockMutex(cond->lock); | |
| 172 ++cond->waiting; | |
| 173 SDL_UnlockMutex(cond->lock); | |
| 174 | |
| 175 /* Unlock the mutex, as is required by condition variable semantics */ | |
| 176 SDL_UnlockMutex(mutex); | |
| 177 | |
| 178 /* Wait for a signal */ | |
| 179 if ( ms == SDL_MUTEX_MAXWAIT ) { | |
| 180 retval = SDL_SemWait(cond->wait_sem); | |
| 181 } else { | |
| 182 retval = SDL_SemWaitTimeout(cond->wait_sem, ms); | |
| 183 } | |
| 184 | |
| 185 /* Let the signaler know we have completed the wait, otherwise | |
| 186 the signaler can race ahead and get the condition semaphore | |
| 187 if we are stopped between the mutex unlock and semaphore wait, | |
| 188 giving a deadlock. See the following URL for details: | |
| 189 http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html | |
| 190 */ | |
| 191 SDL_LockMutex(cond->lock); | |
| 192 if ( cond->signals > 0 ) { | |
| 193 /* If we timed out, we need to eat a condition signal */ | |
| 194 if ( retval > 0 ) { | |
| 195 SDL_SemWait(cond->wait_sem); | |
| 196 } | |
| 197 /* We always notify the signal thread that we are done */ | |
| 198 SDL_SemPost(cond->wait_done); | |
| 199 | |
| 200 /* Signal handshake complete */ | |
| 201 --cond->signals; | |
| 202 } | |
| 203 --cond->waiting; | |
| 204 SDL_UnlockMutex(cond->lock); | |
| 205 | |
| 206 /* Lock the mutex, as is required by condition variable semantics */ | |
| 207 SDL_LockMutex(mutex); | |
| 208 | |
| 209 return retval; | |
| 210 } | |
| 211 | |
| 212 /* Wait on the condition variable forever */ | |
| 213 int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex) | |
| 214 { | |
| 215 return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); | |
| 216 } |