Atlas - SDL_syscond.c
Home / ext / SDL2 / src / thread / psp Lines: 1 | Size: 6244 bytes [Download] [Show on GitHub] [Search similar files] [Raw] [Raw (proxy)][FILE BEGIN]1/* 2 Simple DirectMedia Layer 3 Copyright (C) 1997-2018 Sam Lantinga <[email protected]> 4 5 This software is provided 'as-is', without any express or implied 6 warranty. In no event will the authors be held liable for any damages 7 arising from the use of this software. 8 9 Permission is granted to anyone to use this software for any purpose, 10 including commercial applications, and to alter it and redistribute it 11 freely, subject to the following restrictions: 12 13 1. The origin of this software must not be misrepresented; you must not 14 claim that you wrote the original software. If you use this software 15 in a product, an acknowledgment in the product documentation would be 16 appreciated but is not required. 17 2. Altered source versions must be plainly marked as such, and must not be 18 misrepresented as being the original software. 19 3. This notice may not be removed or altered from any source distribution. 20*/ 21#include "../../SDL_internal.h" 22 23#if SDL_THREAD_PSP 24 25/* An implementation of condition variables using semaphores and mutexes */ 26/* 27 This implementation borrows heavily from the BeOS condition variable 28 implementation, written by Christopher Tate and Owen Smith. Thanks! 29 */ 30 31#include "SDL_thread.h" 32 33struct 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 */ 43SDL_cond * 44SDL_CreateCond(void) 45{ 46 SDL_cond *cond; 47 48 cond = (SDL_cond *) SDL_malloc(sizeof(SDL_cond)); 49 if (cond) { 50 cond->lock = SDL_CreateMutex(); 51 cond->wait_sem = SDL_CreateSemaphore(0); 52 cond->wait_done = SDL_CreateSemaphore(0); 53 cond->waiting = cond->signals = 0; 54 if (!cond->lock || !cond->wait_sem || !cond->wait_done) { 55 SDL_DestroyCond(cond); 56 cond = NULL; 57 } 58 } else { 59 SDL_OutOfMemory(); 60 } 61 return (cond); 62} 63 64/* Destroy a condition variable */ 65void 66SDL_DestroyCond(SDL_cond * cond) 67{ 68 if (cond) { 69 if (cond->wait_sem) { 70 SDL_DestroySemaphore(cond->wait_sem); 71 } 72 if (cond->wait_done) { 73 SDL_DestroySemaphore(cond->wait_done); 74 } 75 if (cond->lock) { 76 SDL_DestroyMutex(cond->lock); 77 } 78 SDL_free(cond); 79 } 80} 81 82/* Restart one of the threads that are waiting on the condition variable */ 83int 84SDL_CondSignal(SDL_cond * cond) 85{ 86 if (!cond) { 87 return SDL_SetError("Passed a NULL condition variable"); 88 } 89 90 /* If there are waiting threads not already signalled, then 91 signal the condition and wait for the thread to respond. 92 */ 93 SDL_LockMutex(cond->lock); 94 if (cond->waiting > cond->signals) { 95 ++cond->signals; 96 SDL_SemPost(cond->wait_sem); 97 SDL_UnlockMutex(cond->lock); 98 SDL_SemWait(cond->wait_done); 99 } else { 100 SDL_UnlockMutex(cond->lock); 101 } 102 103 return 0; 104} 105 106/* Restart all threads that are waiting on the condition variable */ 107int 108SDL_CondBroadcast(SDL_cond * cond) 109{ 110 if (!cond) { 111 return SDL_SetError("Passed a NULL condition variable"); 112 } 113 114 /* If there are waiting threads not already signalled, then 115 signal the condition and wait for the thread to respond. 116 */ 117 SDL_LockMutex(cond->lock); 118 if (cond->waiting > cond->signals) { 119 int i, num_waiting; 120 121 num_waiting = (cond->waiting - cond->signals); 122 cond->signals = cond->waiting; 123 for (i = 0; i < num_waiting; ++i) { 124 SDL_SemPost(cond->wait_sem); 125 } 126 /* Now all released threads are blocked here, waiting for us. 127 Collect them all (and win fabulous prizes!) :-) 128 */ 129 SDL_UnlockMutex(cond->lock); 130 for (i = 0; i < num_waiting; ++i) { 131 SDL_SemWait(cond->wait_done); 132 } 133 } else { 134 SDL_UnlockMutex(cond->lock); 135 } 136 137 return 0; 138} 139 140/* Wait on the condition variable for at most 'ms' milliseconds. 141 The mutex must be locked before entering this function! 142 The mutex is unlocked during the wait, and locked again after the wait. 143 144Typical use: 145 146Thread A: 147 SDL_LockMutex(lock); 148 while ( ! condition ) { 149 SDL_CondWait(cond, lock); 150 } 151 SDL_UnlockMutex(lock); 152 153Thread B: 154 SDL_LockMutex(lock); 155 ... 156 condition = true; 157 ... 158 SDL_CondSignal(cond); 159 SDL_UnlockMutex(lock); 160 */ 161int 162SDL_CondWaitTimeout(SDL_cond * cond, SDL_mutex * mutex, Uint32 ms) 163{ 164 int retval; 165 166 if (!cond) { 167 return SDL_SetError("Passed a NULL condition variable"); 168 } 169 170 /* Obtain the protection mutex, and increment the number of waiters. 171 This allows the signal mechanism to only perform a signal if there 172 are waiting threads. 173 */ 174 SDL_LockMutex(cond->lock); 175 ++cond->waiting; 176 SDL_UnlockMutex(cond->lock); 177 178 /* Unlock the mutex, as is required by condition variable semantics */ 179 SDL_UnlockMutex(mutex); 180 181 /* Wait for a signal */ 182 if (ms == SDL_MUTEX_MAXWAIT) { 183 retval = SDL_SemWait(cond->wait_sem); 184 } else { 185 retval = SDL_SemWaitTimeout(cond->wait_sem, ms); 186 } 187 188 /* Let the signaler know we have completed the wait, otherwise 189 the signaler can race ahead and get the condition semaphore 190 if we are stopped between the mutex unlock and semaphore wait, 191 giving a deadlock. See the following URL for details: 192 http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html 193 */ 194 SDL_LockMutex(cond->lock); 195 if (cond->signals > 0) { 196 /* If we timed out, we need to eat a condition signal */ 197 if (retval > 0) { 198 SDL_SemWait(cond->wait_sem); 199 } 200 /* We always notify the signal thread that we are done */ 201 SDL_SemPost(cond->wait_done); 202 203 /* Signal handshake complete */ 204 --cond->signals; 205 } 206 --cond->waiting; 207 SDL_UnlockMutex(cond->lock); 208 209 /* Lock the mutex, as is required by condition variable semantics */ 210 SDL_LockMutex(mutex); 211 212 return retval; 213} 214 215/* Wait on the condition variable forever */ 216int 217SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex) 218{ 219 return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); 220} 221 222#endif /* SDL_THREAD_PSP */ 223 224/* vi: set ts=4 sw=4 expandtab: */ 225[FILE END](C) 2025 0x4248 (C) 2025 4248 Media and 4248 Systems, All part of 0x4248 See LICENCE files for more information. 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