Mercurial > sdl-ios-xcode
annotate src/thread/generic/SDL_sysmutex.c @ 3685:64ce267332c6
Switched from SDL_WindowID and SDL_TextureID to SDL_Window* and SDL_Texture* for code simplicity and improved performance.
author | Sam Lantinga <slouken@libsdl.org> |
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date | Thu, 21 Jan 2010 06:21:52 +0000 |
parents | 0d1b16ee0bca |
children | f7b03b6838cb |
rev | line source |
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0 | 1 /* |
2 SDL - Simple DirectMedia Layer | |
2859 | 3 Copyright (C) 1997-2009 Sam Lantinga |
0 | 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 |
0 | 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. |
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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13 Lesser General Public License for more details. |
0 | 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 |
0 | 18 |
19 Sam Lantinga | |
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20 slouken@libsdl.org |
0 | 21 */ |
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22 #include "SDL_config.h" |
0 | 23 |
24 /* An implementation of mutexes using semaphores */ | |
25 | |
26 #include "SDL_thread.h" | |
27 #include "SDL_systhread_c.h" | |
28 | |
29 | |
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30 struct SDL_mutex |
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31 { |
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32 int recursive; |
3578 | 33 SDL_threadID owner; |
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34 SDL_sem *sem; |
0 | 35 }; |
36 | |
37 /* Create a mutex */ | |
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38 SDL_mutex * |
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39 SDL_CreateMutex(void) |
0 | 40 { |
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41 SDL_mutex *mutex; |
0 | 42 |
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43 /* Allocate mutex memory */ |
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44 mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex)); |
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45 if (mutex) { |
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46 /* Create the mutex semaphore, with initial value 1 */ |
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47 mutex->sem = SDL_CreateSemaphore(1); |
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48 mutex->recursive = 0; |
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49 mutex->owner = 0; |
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50 if (!mutex->sem) { |
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51 SDL_free(mutex); |
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52 mutex = NULL; |
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53 } |
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54 } else { |
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55 SDL_OutOfMemory(); |
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56 } |
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57 return mutex; |
0 | 58 } |
59 | |
60 /* Free the mutex */ | |
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61 void |
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62 SDL_DestroyMutex(SDL_mutex * mutex) |
0 | 63 { |
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64 if (mutex) { |
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65 if (mutex->sem) { |
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66 SDL_DestroySemaphore(mutex->sem); |
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67 } |
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68 SDL_free(mutex); |
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69 } |
0 | 70 } |
71 | |
72 /* Lock the semaphore */ | |
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73 int |
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74 SDL_mutexP(SDL_mutex * mutex) |
0 | 75 { |
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76 #if SDL_THREADS_DISABLED |
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77 return 0; |
0 | 78 #else |
3578 | 79 SDL_threadID this_thread; |
0 | 80 |
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81 if (mutex == NULL) { |
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82 SDL_SetError("Passed a NULL mutex"); |
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83 return -1; |
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84 } |
0 | 85 |
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86 this_thread = SDL_ThreadID(); |
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87 if (mutex->owner == this_thread) { |
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88 ++mutex->recursive; |
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89 } else { |
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90 /* The order of operations is important. |
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91 We set the locking thread id after we obtain the lock |
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92 so unlocks from other threads will fail. |
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93 */ |
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94 SDL_SemWait(mutex->sem); |
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95 mutex->owner = this_thread; |
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96 mutex->recursive = 0; |
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97 } |
0 | 98 |
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99 return 0; |
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100 #endif /* SDL_THREADS_DISABLED */ |
0 | 101 } |
102 | |
103 /* Unlock the mutex */ | |
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104 int |
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105 SDL_mutexV(SDL_mutex * mutex) |
0 | 106 { |
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107 #if SDL_THREADS_DISABLED |
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108 return 0; |
0 | 109 #else |
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110 if (mutex == NULL) { |
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111 SDL_SetError("Passed a NULL mutex"); |
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112 return -1; |
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113 } |
0 | 114 |
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115 /* If we don't own the mutex, we can't unlock it */ |
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116 if (SDL_ThreadID() != mutex->owner) { |
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117 SDL_SetError("mutex not owned by this thread"); |
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118 return -1; |
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119 } |
0 | 120 |
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121 if (mutex->recursive) { |
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122 --mutex->recursive; |
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123 } else { |
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124 /* The order of operations is important. |
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125 First reset the owner so another thread doesn't lock |
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126 the mutex and set the ownership before we reset it, |
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127 then release the lock semaphore. |
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128 */ |
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129 mutex->owner = 0; |
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130 SDL_SemPost(mutex->sem); |
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131 } |
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132 return 0; |
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133 #endif /* SDL_THREADS_DISABLED */ |
0 | 134 } |
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135 |
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136 /* vi: set ts=4 sw=4 expandtab: */ |