Mercurial > sdl-ios-xcode
annotate src/thread/os2/SDL_syscond.c @ 2663:0caed045d01b gsoc2008_audio_resampling
General cleanup and fixed a buffer overrun bug. It may be necessary to normalize filter gain differently or something.
author | Aaron Wishnick <schnarf@gmail.com> |
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date | Tue, 12 Aug 2008 00:24:42 +0000 |
parents | c121d94672cb |
children | 99210400e8b9 |
rev | line source |
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1190 | 1 /* |
2 SDL - Simple DirectMedia Layer | |
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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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15 You should have received a copy of the GNU Lesser General Public |
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16 License along with this library; if not, write to the Free Software |
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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 { | |
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34 SDL_mutex *lock; |
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35 int waiting; |
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36 int signals; |
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37 SDL_sem *wait_sem; |
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38 SDL_sem *wait_done; |
1190 | 39 }; |
40 | |
41 /* Create a condition variable */ | |
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42 DECLSPEC SDL_cond *SDLCALL |
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43 SDL_CreateCond(void) |
1190 | 44 { |
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45 SDL_cond *cond; |
1190 | 46 |
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47 cond = (SDL_cond *) SDL_malloc(sizeof(SDL_cond)); |
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48 if (cond) { |
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49 cond->lock = SDL_CreateMutex(); |
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50 cond->wait_sem = SDL_CreateSemaphore(0); |
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51 cond->wait_done = SDL_CreateSemaphore(0); |
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52 cond->waiting = cond->signals = 0; |
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53 if (!cond->lock || !cond->wait_sem || !cond->wait_done) { |
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54 SDL_DestroyCond(cond); |
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55 cond = NULL; |
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56 } |
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57 } else { |
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58 SDL_OutOfMemory(); |
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59 } |
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60 return (cond); |
1190 | 61 } |
62 | |
63 /* Destroy a condition variable */ | |
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64 DECLSPEC void SDLCALL |
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65 SDL_DestroyCond(SDL_cond * cond) |
1190 | 66 { |
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67 if (cond) { |
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68 if (cond->wait_sem) { |
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69 SDL_DestroySemaphore(cond->wait_sem); |
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70 } |
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71 if (cond->wait_done) { |
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72 SDL_DestroySemaphore(cond->wait_done); |
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73 } |
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74 if (cond->lock) { |
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75 SDL_DestroyMutex(cond->lock); |
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76 } |
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77 SDL_free(cond); |
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78 } |
1190 | 79 } |
80 | |
81 /* Restart one of the threads that are waiting on the condition variable */ | |
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82 DECLSPEC int SDLCALL |
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83 SDL_CondSignal(SDL_cond * cond) |
1190 | 84 { |
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85 if (!cond) { |
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86 SDL_SetError("Passed a NULL condition variable"); |
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87 return -1; |
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88 } |
1190 | 89 |
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90 /* If there are waiting threads not already signalled, then |
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91 signal the condition and wait for the thread to respond. |
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92 */ |
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93 SDL_LockMutex(cond->lock); |
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94 if (cond->waiting > cond->signals) { |
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95 ++cond->signals; |
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96 SDL_SemPost(cond->wait_sem); |
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97 SDL_UnlockMutex(cond->lock); |
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98 SDL_SemWait(cond->wait_done); |
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99 } else { |
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100 SDL_UnlockMutex(cond->lock); |
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101 } |
1190 | 102 |
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103 return 0; |
1190 | 104 } |
105 | |
106 /* Restart all threads that are waiting on the condition variable */ | |
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107 DECLSPEC int SDLCALL |
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108 SDL_CondBroadcast(SDL_cond * cond) |
1190 | 109 { |
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110 if (!cond) { |
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111 SDL_SetError("Passed a NULL condition variable"); |
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112 return -1; |
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113 } |
1190 | 114 |
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115 /* If there are waiting threads not already signalled, then |
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116 signal the condition and wait for the thread to respond. |
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117 */ |
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118 SDL_LockMutex(cond->lock); |
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119 if (cond->waiting > cond->signals) { |
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120 int i, num_waiting; |
1190 | 121 |
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122 num_waiting = (cond->waiting - cond->signals); |
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123 cond->signals = cond->waiting; |
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124 for (i = 0; i < num_waiting; ++i) { |
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125 SDL_SemPost(cond->wait_sem); |
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126 } |
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127 /* Now all released threads are blocked here, waiting for us. |
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128 Collect them all (and win fabulous prizes!) :-) |
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129 */ |
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130 SDL_UnlockMutex(cond->lock); |
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131 for (i = 0; i < num_waiting; ++i) { |
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132 SDL_SemWait(cond->wait_done); |
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133 } |
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134 } else { |
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135 SDL_UnlockMutex(cond->lock); |
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136 } |
1190 | 137 |
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138 return 0; |
1190 | 139 } |
140 | |
141 /* Wait on the condition variable for at most 'ms' milliseconds. | |
142 The mutex must be locked before entering this function! | |
143 The mutex is unlocked during the wait, and locked again after the wait. | |
144 | |
145 Typical use: | |
146 | |
147 Thread A: | |
148 SDL_LockMutex(lock); | |
149 while ( ! condition ) { | |
150 SDL_CondWait(cond); | |
151 } | |
152 SDL_UnlockMutex(lock); | |
153 | |
154 Thread B: | |
155 SDL_LockMutex(lock); | |
156 ... | |
157 condition = true; | |
158 ... | |
159 SDL_UnlockMutex(lock); | |
160 */ | |
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161 DECLSPEC int SDLCALL |
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162 SDL_CondWaitTimeout(SDL_cond * cond, SDL_mutex * mutex, Uint32 ms) |
1190 | 163 { |
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164 int retval; |
1190 | 165 |
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166 if (!cond) { |
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167 SDL_SetError("Passed a NULL condition variable"); |
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168 return -1; |
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169 } |
1190 | 170 |
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171 /* Obtain the protection mutex, and increment the number of waiters. |
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172 This allows the signal mechanism to only perform a signal if there |
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173 are waiting threads. |
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174 */ |
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175 SDL_LockMutex(cond->lock); |
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176 ++cond->waiting; |
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177 SDL_UnlockMutex(cond->lock); |
1190 | 178 |
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179 /* Unlock the mutex, as is required by condition variable semantics */ |
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180 SDL_UnlockMutex(mutex); |
1190 | 181 |
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182 /* Wait for a signal */ |
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183 if (ms == SDL_MUTEX_MAXWAIT) { |
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184 retval = SDL_SemWait(cond->wait_sem); |
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185 } else { |
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186 retval = SDL_SemWaitTimeout(cond->wait_sem, ms); |
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187 } |
1190 | 188 |
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189 /* Let the signaler know we have completed the wait, otherwise |
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190 the signaler can race ahead and get the condition semaphore |
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191 if we are stopped between the mutex unlock and semaphore wait, |
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192 giving a deadlock. See the following URL for details: |
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193 http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html |
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194 */ |
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195 SDL_LockMutex(cond->lock); |
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196 if (cond->signals > 0) { |
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197 /* If we timed out, we need to eat a condition signal */ |
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198 if (retval > 0) { |
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199 SDL_SemWait(cond->wait_sem); |
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200 } |
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201 /* We always notify the signal thread that we are done */ |
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202 SDL_SemPost(cond->wait_done); |
1190 | 203 |
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204 /* Signal handshake complete */ |
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205 --cond->signals; |
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206 } |
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207 --cond->waiting; |
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208 SDL_UnlockMutex(cond->lock); |
1190 | 209 |
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210 /* Lock the mutex, as is required by condition variable semantics */ |
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211 SDL_LockMutex(mutex); |
1190 | 212 |
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213 return retval; |
1190 | 214 } |
215 | |
216 /* Wait on the condition variable forever */ | |
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217 DECLSPEC int SDLCALL |
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218 SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex) |
1190 | 219 { |
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220 return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); |
1190 | 221 } |
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222 |
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223 /* vi: set ts=4 sw=4 expandtab: */ |