SDL  2.0
SDL_syssem.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
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 /* An implementation of semaphores using mutexes and condition variables */
24 
25 #include "SDL_timer.h"
26 #include "SDL_thread.h"
27 #include "SDL_systhread_c.h"
28 
29 
30 #if SDL_THREADS_DISABLED
31 
32 SDL_sem *
33 SDL_CreateSemaphore(Uint32 initial_value)
34 {
35  SDL_SetError("SDL not built with thread support");
36  return (SDL_sem *) 0;
37 }
38 
39 void
40 SDL_DestroySemaphore(SDL_sem * sem)
41 {
42 }
43 
44 int
45 SDL_SemTryWait(SDL_sem * sem)
46 {
47  return SDL_SetError("SDL not built with thread support");
48 }
49 
50 int
52 {
53  return SDL_SetError("SDL not built with thread support");
54 }
55 
56 int
57 SDL_SemWait(SDL_sem * sem)
58 {
59  return SDL_SetError("SDL not built with thread support");
60 }
61 
62 Uint32
63 SDL_SemValue(SDL_sem * sem)
64 {
65  return 0;
66 }
67 
68 int
69 SDL_SemPost(SDL_sem * sem)
70 {
71  return SDL_SetError("SDL not built with thread support");
72 }
73 
74 #else
75 
77 {
82 };
83 
84 SDL_sem *
86 {
87  SDL_sem *sem;
88 
89  sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
90  if (!sem) {
92  return NULL;
93  }
94  sem->count = initial_value;
95  sem->waiters_count = 0;
96 
97  sem->count_lock = SDL_CreateMutex();
98  sem->count_nonzero = SDL_CreateCond();
99  if (!sem->count_lock || !sem->count_nonzero) {
101  return NULL;
102  }
103 
104  return sem;
105 }
106 
107 /* WARNING:
108  You cannot call this function when another thread is using the semaphore.
109 */
110 void
112 {
113  if (sem) {
114  sem->count = 0xFFFFFFFF;
115  while (sem->waiters_count > 0) {
116  SDL_CondSignal(sem->count_nonzero);
117  SDL_Delay(10);
118  }
119  SDL_DestroyCond(sem->count_nonzero);
120  if (sem->count_lock) {
121  SDL_LockMutex(sem->count_lock);
122  SDL_UnlockMutex(sem->count_lock);
123  SDL_DestroyMutex(sem->count_lock);
124  }
125  SDL_free(sem);
126  }
127 }
128 
129 int
130 SDL_SemTryWait(SDL_sem * sem)
131 {
132  int retval;
133 
134  if (!sem) {
135  return SDL_SetError("Passed a NULL semaphore");
136  }
137 
139  SDL_LockMutex(sem->count_lock);
140  if (sem->count > 0) {
141  --sem->count;
142  retval = 0;
143  }
144  SDL_UnlockMutex(sem->count_lock);
145 
146  return retval;
147 }
148 
149 int
151 {
152  int retval;
153 
154  if (!sem) {
155  return SDL_SetError("Passed a NULL semaphore");
156  }
157 
158  /* A timeout of 0 is an easy case */
159  if (timeout == 0) {
160  return SDL_SemTryWait(sem);
161  }
162 
163  SDL_LockMutex(sem->count_lock);
164  ++sem->waiters_count;
165  retval = 0;
166  while ((sem->count == 0) && (retval != SDL_MUTEX_TIMEDOUT)) {
167  retval = SDL_CondWaitTimeout(sem->count_nonzero,
168  sem->count_lock, timeout);
169  }
170  --sem->waiters_count;
171  if (retval == 0) {
172  --sem->count;
173  }
174  SDL_UnlockMutex(sem->count_lock);
175 
176  return retval;
177 }
178 
179 int
180 SDL_SemWait(SDL_sem * sem)
181 {
183 }
184 
185 Uint32
186 SDL_SemValue(SDL_sem * sem)
187 {
188  Uint32 value;
189 
190  value = 0;
191  if (sem) {
192  SDL_LockMutex(sem->count_lock);
193  value = sem->count;
194  SDL_UnlockMutex(sem->count_lock);
195  }
196  return value;
197 }
198 
199 int
200 SDL_SemPost(SDL_sem * sem)
201 {
202  if (!sem) {
203  return SDL_SetError("Passed a NULL semaphore");
204  }
205 
206  SDL_LockMutex(sem->count_lock);
207  if (sem->waiters_count > 0) {
208  SDL_CondSignal(sem->count_nonzero);
209  }
210  ++sem->count;
211  SDL_UnlockMutex(sem->count_lock);
212 
213  return 0;
214 }
215 
216 #endif /* SDL_THREADS_DISABLED */
217 /* vi: set ts=4 sw=4 expandtab: */
SDL_SemTryWait
int SDL_SemTryWait(SDL_sem *sem)
Definition: SDL_syssem.c:130
SDL_LockMutex
#define SDL_LockMutex
Definition: SDL_dynapi_overrides.h:260
NULL
#define NULL
Definition: begin_code.h:164
SDL_timer.h
timeout
GLbitfield GLuint64 timeout
Definition: SDL_opengl_glext.h:1483
sem
static SDL_sem * sem
Definition: testsem.c:23
SDL_mutex
Definition: SDL_sysmutex.c:30
SDL_CreateMutex
#define SDL_CreateMutex
Definition: SDL_dynapi_overrides.h:259
SDL_DestroyCond
#define SDL_DestroyCond
Definition: SDL_dynapi_overrides.h:272
SDL_CondSignal
#define SDL_CondSignal
Definition: SDL_dynapi_overrides.h:273
SDL_CreateSemaphore
SDL_sem * SDL_CreateSemaphore(Uint32 initial_value)
Definition: SDL_syssem.c:85
SDL_SemWait
int SDL_SemWait(SDL_sem *sem)
Definition: SDL_syssem.c:180
Uint32
uint32_t Uint32
Definition: SDL_stdinc.h:203
SDL_MUTEX_TIMEDOUT
#define SDL_MUTEX_TIMEDOUT
Definition: SDL_mutex.h:44
SDL_cond
Definition: SDL_syscond.c:32
SDL_thread.h
retval
SDL_bool retval
Definition: testgamecontroller.c:65
SDL_systhread_c.h
SDL_free
#define SDL_free
Definition: SDL_dynapi_overrides.h:377
SDL_CondWaitTimeout
#define SDL_CondWaitTimeout
Definition: SDL_dynapi_overrides.h:276
SDL_MUTEX_MAXWAIT
#define SDL_MUTEX_MAXWAIT
Definition: SDL_mutex.h:49
SDL_semaphore::waiters_count
Uint32 waiters_count
Definition: SDL_syssem.c:79
SDL_SemPost
int SDL_SemPost(SDL_sem *sem)
Definition: SDL_syssem.c:200
SDL_Delay
#define SDL_Delay
Definition: SDL_dynapi_overrides.h:486
SDL_semaphore::count_lock
SDL_mutex * count_lock
Definition: SDL_syssem.c:80
SDL_semaphore::count
Uint32 count
Definition: SDL_syssem.c:78
SDL_SemValue
Uint32 SDL_SemValue(SDL_sem *sem)
Definition: SDL_syssem.c:186
SDL_OutOfMemory
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
SDL_CreateCond
#define SDL_CreateCond
Definition: SDL_dynapi_overrides.h:271
SDL_semaphore::count_nonzero
SDL_cond * count_nonzero
Definition: SDL_syssem.c:81
value
GLsizei const GLfloat * value
Definition: SDL_opengl_glext.h:698
SDL_SetError
#define SDL_SetError
Definition: SDL_dynapi_overrides.h:30
SDL_SemWaitTimeout
int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
Definition: SDL_syssem.c:150
SDL_DestroySemaphore
void SDL_DestroySemaphore(SDL_sem *sem)
Definition: SDL_syssem.c:111
SDL_DestroyMutex
#define SDL_DestroyMutex
Definition: SDL_dynapi_overrides.h:263
SDL_semaphore
Definition: SDL_syssem.c:77
SDL_malloc
#define SDL_malloc
Definition: SDL_dynapi_overrides.h:374
SDL_UnlockMutex
#define SDL_UnlockMutex
Definition: SDL_dynapi_overrides.h:262