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 #include <errno.h>
24 #include <pthread.h>
25 #include <semaphore.h>
26 #include <sys/time.h>
27 #include <time.h>
28 
29 #include "SDL_thread.h"
30 #include "SDL_timer.h"
31 
32 /* Wrapper around POSIX 1003.1b semaphores */
33 
34 #if defined(__MACOSX__) || defined(__IPHONEOS__)
35 /* Mac OS X doesn't support sem_getvalue() as of version 10.4 */
36 #include "../generic/SDL_syssem.c"
37 #else
38 
39 struct SDL_semaphore
40 {
41  sem_t sem;
42 };
43 
44 /* Create a semaphore, initialized with value */
45 SDL_sem *
47 {
48  SDL_sem *sem = (SDL_sem *) SDL_malloc(sizeof(SDL_sem));
49  if (sem) {
50  if (sem_init(&sem->sem, 0, initial_value) < 0) {
51  SDL_SetError("sem_init() failed");
52  SDL_free(sem);
53  sem = NULL;
54  }
55  } else {
57  }
58  return sem;
59 }
60 
61 void
63 {
64  if (sem) {
65  sem_destroy(&sem->sem);
66  SDL_free(sem);
67  }
68 }
69 
70 int
71 SDL_SemTryWait(SDL_sem * sem)
72 {
73  int retval;
74 
75  if (!sem) {
76  return SDL_SetError("Passed a NULL semaphore");
77  }
78  retval = SDL_MUTEX_TIMEDOUT;
79  if (sem_trywait(&sem->sem) == 0) {
80  retval = 0;
81  }
82  return retval;
83 }
84 
85 int
86 SDL_SemWait(SDL_sem * sem)
87 {
88  int retval;
89 
90  if (!sem) {
91  return SDL_SetError("Passed a NULL semaphore");
92  }
93 
94  do {
95  retval = sem_wait(&sem->sem);
96  } while (retval < 0 && errno == EINTR);
97 
98  if (retval < 0) {
99  retval = SDL_SetError("sem_wait() failed");
100  }
101  return retval;
102 }
103 
104 int
106 {
107  int retval;
108 #ifdef HAVE_SEM_TIMEDWAIT
109 #ifndef HAVE_CLOCK_GETTIME
110  struct timeval now;
111 #endif
112  struct timespec ts_timeout;
113 #else
114  Uint32 end;
115 #endif
116 
117  if (!sem) {
118  return SDL_SetError("Passed a NULL semaphore");
119  }
120 
121  /* Try the easy cases first */
122  if (timeout == 0) {
123  return SDL_SemTryWait(sem);
124  }
125  if (timeout == SDL_MUTEX_MAXWAIT) {
126  return SDL_SemWait(sem);
127  }
128 
129 #ifdef HAVE_SEM_TIMEDWAIT
130  /* Setup the timeout. sem_timedwait doesn't wait for
131  * a lapse of time, but until we reach a certain time.
132  * This time is now plus the timeout.
133  */
134 #ifdef HAVE_CLOCK_GETTIME
135  clock_gettime(CLOCK_REALTIME, &ts_timeout);
136 
137  /* Add our timeout to current time */
138  ts_timeout.tv_nsec += (timeout % 1000) * 1000000;
139  ts_timeout.tv_sec += timeout / 1000;
140 #else
141  gettimeofday(&now, NULL);
142 
143  /* Add our timeout to current time */
144  ts_timeout.tv_sec = now.tv_sec + (timeout / 1000);
145  ts_timeout.tv_nsec = (now.tv_usec + (timeout % 1000) * 1000) * 1000;
146 #endif
147 
148  /* Wrap the second if needed */
149  if (ts_timeout.tv_nsec > 1000000000) {
150  ts_timeout.tv_sec += 1;
151  ts_timeout.tv_nsec -= 1000000000;
152  }
153 
154  /* Wait. */
155  do {
156  retval = sem_timedwait(&sem->sem, &ts_timeout);
157  } while (retval < 0 && errno == EINTR);
158 
159  if (retval < 0) {
160  if (errno == ETIMEDOUT) {
161  retval = SDL_MUTEX_TIMEDOUT;
162  } else {
163  SDL_SetError("sem_timedwait returned an error: %s", strerror(errno));
164  }
165  }
166 #else
167  end = SDL_GetTicks() + timeout;
168  while ((retval = SDL_SemTryWait(sem)) == SDL_MUTEX_TIMEDOUT) {
169  if (SDL_TICKS_PASSED(SDL_GetTicks(), end)) {
170  break;
171  }
172  SDL_Delay(1);
173  }
174 #endif /* HAVE_SEM_TIMEDWAIT */
175 
176  return retval;
177 }
178 
179 Uint32
180 SDL_SemValue(SDL_sem * sem)
181 {
182  int ret = 0;
183  if (sem) {
184  sem_getvalue(&sem->sem, &ret);
185  if (ret < 0) {
186  ret = 0;
187  }
188  }
189  return (Uint32) ret;
190 }
191 
192 int
193 SDL_SemPost(SDL_sem * sem)
194 {
195  int retval;
196 
197  if (!sem) {
198  return SDL_SetError("Passed a NULL semaphore");
199  }
200 
201  retval = sem_post(&sem->sem);
202  if (retval < 0) {
203  SDL_SetError("sem_post() failed");
204  }
205  return retval;
206 }
207 
208 #endif /* __MACOSX__ */
209 /* vi: set ts=4 sw=4 expandtab: */
GLuint GLuint end
Definition: SDL_opengl.h:1571
uint32_t Uint32
Definition: SDL_stdinc.h:181
int SDL_SemPost(SDL_sem *sem)
Definition: SDL_syssem.c:200
#define SDL_MUTEX_TIMEDOUT
Definition: SDL_mutex.h:44
SDL_bool retval
#define SDL_MUTEX_MAXWAIT
Definition: SDL_mutex.h:49
Uint32 SDL_GetTicks(void)
Get the number of milliseconds since the SDL library initialization.
int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
Definition: SDL_syssem.c:150
int SDL_SemTryWait(SDL_sem *sem)
Definition: SDL_syssem.c:130
#define SDL_free
int SDL_SemWait(SDL_sem *sem)
Definition: SDL_syssem.c:180
#define SDL_Delay
#define NULL
Definition: begin_code.h:164
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
#define SDL_SetError
Uint32 SDL_SemValue(SDL_sem *sem)
Definition: SDL_syssem.c:186
GLbitfield GLuint64 timeout
#define SDL_malloc
#define SDL_TICKS_PASSED(A, B)
Compare SDL ticks values, and return true if A has passed B.
Definition: SDL_timer.h:56
void SDL_DestroySemaphore(SDL_sem *sem)
Definition: SDL_syssem.c:111
SDL_sem * SDL_CreateSemaphore(Uint32 initial_value)
Definition: SDL_syssem.c:85