e14743d1 |
1 | /* |
2 | SDL - Simple DirectMedia Layer |
3 | Copyright (C) 1997-2009 Sam Lantinga |
4 | |
5 | This library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
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 |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with this library; if not, write to the Free Software |
17 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
18 | |
19 | Sam Lantinga |
20 | slouken@libsdl.org |
21 | */ |
22 | #include "SDL_config.h" |
23 | |
24 | /* An implementation of semaphores using mutexes and condition variables */ |
25 | |
26 | #include "SDL_timer.h" |
27 | #include "SDL_thread.h" |
28 | #include "SDL_systhread_c.h" |
29 | |
30 | |
31 | #if SDL_THREADS_DISABLED |
32 | |
33 | SDL_sem *SDL_CreateSemaphore(Uint32 initial_value) |
34 | { |
35 | SDL_SetError("SDL not configured with thread support"); |
36 | return (SDL_sem *)0; |
37 | } |
38 | |
39 | void SDL_DestroySemaphore(SDL_sem *sem) |
40 | { |
41 | return; |
42 | } |
43 | |
44 | int SDL_SemTryWait(SDL_sem *sem) |
45 | { |
46 | SDL_SetError("SDL not configured with thread support"); |
47 | return -1; |
48 | } |
49 | |
50 | int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout) |
51 | { |
52 | SDL_SetError("SDL not configured with thread support"); |
53 | return -1; |
54 | } |
55 | |
56 | int SDL_SemWait(SDL_sem *sem) |
57 | { |
58 | SDL_SetError("SDL not configured with thread support"); |
59 | return -1; |
60 | } |
61 | |
62 | Uint32 SDL_SemValue(SDL_sem *sem) |
63 | { |
64 | return 0; |
65 | } |
66 | |
67 | int SDL_SemPost(SDL_sem *sem) |
68 | { |
69 | SDL_SetError("SDL not configured with thread support"); |
70 | return -1; |
71 | } |
72 | |
73 | #else |
74 | |
75 | struct SDL_semaphore |
76 | { |
77 | Uint32 count; |
78 | Uint32 waiters_count; |
79 | SDL_mutex *count_lock; |
80 | SDL_cond *count_nonzero; |
81 | }; |
82 | |
83 | SDL_sem *SDL_CreateSemaphore(Uint32 initial_value) |
84 | { |
85 | SDL_sem *sem; |
86 | |
87 | sem = (SDL_sem *)SDL_malloc(sizeof(*sem)); |
88 | if ( ! sem ) { |
89 | SDL_OutOfMemory(); |
90 | return NULL; |
91 | } |
92 | sem->count = initial_value; |
93 | sem->waiters_count = 0; |
94 | |
95 | sem->count_lock = SDL_CreateMutex(); |
96 | sem->count_nonzero = SDL_CreateCond(); |
97 | if ( ! sem->count_lock || ! sem->count_nonzero ) { |
98 | SDL_DestroySemaphore(sem); |
99 | return NULL; |
100 | } |
101 | |
102 | return sem; |
103 | } |
104 | |
105 | /* WARNING: |
106 | You cannot call this function when another thread is using the semaphore. |
107 | */ |
108 | void SDL_DestroySemaphore(SDL_sem *sem) |
109 | { |
110 | if ( sem ) { |
111 | sem->count = 0xFFFFFFFF; |
112 | while ( sem->waiters_count > 0) { |
113 | SDL_CondSignal(sem->count_nonzero); |
114 | SDL_Delay(10); |
115 | } |
116 | SDL_DestroyCond(sem->count_nonzero); |
117 | if ( sem->count_lock ) { |
118 | SDL_mutexP(sem->count_lock); |
119 | SDL_mutexV(sem->count_lock); |
120 | SDL_DestroyMutex(sem->count_lock); |
121 | } |
122 | SDL_free(sem); |
123 | } |
124 | } |
125 | |
126 | int SDL_SemTryWait(SDL_sem *sem) |
127 | { |
128 | int retval; |
129 | |
130 | if ( ! sem ) { |
131 | SDL_SetError("Passed a NULL semaphore"); |
132 | return -1; |
133 | } |
134 | |
135 | retval = SDL_MUTEX_TIMEDOUT; |
136 | SDL_LockMutex(sem->count_lock); |
137 | if ( sem->count > 0 ) { |
138 | --sem->count; |
139 | retval = 0; |
140 | } |
141 | SDL_UnlockMutex(sem->count_lock); |
142 | |
143 | return retval; |
144 | } |
145 | |
146 | int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout) |
147 | { |
148 | int retval; |
149 | |
150 | if ( ! sem ) { |
151 | SDL_SetError("Passed a NULL semaphore"); |
152 | return -1; |
153 | } |
154 | |
155 | /* A timeout of 0 is an easy case */ |
156 | if ( timeout == 0 ) { |
157 | return SDL_SemTryWait(sem); |
158 | } |
159 | |
160 | SDL_LockMutex(sem->count_lock); |
161 | ++sem->waiters_count; |
162 | retval = 0; |
163 | while ( (sem->count == 0) && (retval != SDL_MUTEX_TIMEDOUT) ) { |
164 | retval = SDL_CondWaitTimeout(sem->count_nonzero, |
165 | sem->count_lock, timeout); |
166 | } |
167 | --sem->waiters_count; |
168 | if (retval == 0) { |
169 | --sem->count; |
170 | } |
171 | SDL_UnlockMutex(sem->count_lock); |
172 | |
173 | return retval; |
174 | } |
175 | |
176 | int SDL_SemWait(SDL_sem *sem) |
177 | { |
178 | return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT); |
179 | } |
180 | |
181 | Uint32 SDL_SemValue(SDL_sem *sem) |
182 | { |
183 | Uint32 value; |
184 | |
185 | value = 0; |
186 | if ( sem ) { |
187 | SDL_LockMutex(sem->count_lock); |
188 | value = sem->count; |
189 | SDL_UnlockMutex(sem->count_lock); |
190 | } |
191 | return value; |
192 | } |
193 | |
194 | int SDL_SemPost(SDL_sem *sem) |
195 | { |
196 | if ( ! sem ) { |
197 | SDL_SetError("Passed a NULL semaphore"); |
198 | return -1; |
199 | } |
200 | |
201 | SDL_LockMutex(sem->count_lock); |
202 | if ( sem->waiters_count > 0 ) { |
203 | SDL_CondSignal(sem->count_nonzero); |
204 | } |
205 | ++sem->count; |
206 | SDL_UnlockMutex(sem->count_lock); |
207 | |
208 | return 0; |
209 | } |
210 | |
211 | #endif /* SDL_THREADS_DISABLED */ |