SDL  2.0
SDL_syssem.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2017 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  retval = sem_wait(&sem->sem);
95  if (retval < 0) {
96  retval = SDL_SetError("sem_wait() failed");
97  }
98  return retval;
99 }
100 
101 int
103 {
104  int retval;
105 #ifdef HAVE_SEM_TIMEDWAIT
106 #ifndef HAVE_CLOCK_GETTIME
107  struct timeval now;
108 #endif
109  struct timespec ts_timeout;
110 #else
111  Uint32 end;
112 #endif
113 
114  if (!sem) {
115  return SDL_SetError("Passed a NULL semaphore");
116  }
117 
118  /* Try the easy cases first */
119  if (timeout == 0) {
120  return SDL_SemTryWait(sem);
121  }
122  if (timeout == SDL_MUTEX_MAXWAIT) {
123  return SDL_SemWait(sem);
124  }
125 
126 #ifdef HAVE_SEM_TIMEDWAIT
127  /* Setup the timeout. sem_timedwait doesn't wait for
128  * a lapse of time, but until we reach a certain time.
129  * This time is now plus the timeout.
130  */
131 #ifdef HAVE_CLOCK_GETTIME
132  clock_gettime(CLOCK_REALTIME, &ts_timeout);
133 
134  /* Add our timeout to current time */
135  ts_timeout.tv_nsec += (timeout % 1000) * 1000000;
136  ts_timeout.tv_sec += timeout / 1000;
137 #else
138  gettimeofday(&now, NULL);
139 
140  /* Add our timeout to current time */
141  ts_timeout.tv_sec = now.tv_sec + (timeout / 1000);
142  ts_timeout.tv_nsec = (now.tv_usec + (timeout % 1000) * 1000) * 1000;
143 #endif
144 
145  /* Wrap the second if needed */
146  if (ts_timeout.tv_nsec > 1000000000) {
147  ts_timeout.tv_sec += 1;
148  ts_timeout.tv_nsec -= 1000000000;
149  }
150 
151  /* Wait. */
152  do {
153  retval = sem_timedwait(&sem->sem, &ts_timeout);
154  } while (retval < 0 && errno == EINTR);
155 
156  if (retval < 0) {
157  if (errno == ETIMEDOUT) {
158  retval = SDL_MUTEX_TIMEDOUT;
159  } else {
160  SDL_SetError("sem_timedwait returned an error: %s", strerror(errno));
161  }
162  }
163 #else
164  end = SDL_GetTicks() + timeout;
165  while ((retval = SDL_SemTryWait(sem)) == SDL_MUTEX_TIMEDOUT) {
166  if (SDL_TICKS_PASSED(SDL_GetTicks(), end)) {
167  break;
168  }
169  SDL_Delay(1);
170  }
171 #endif /* HAVE_SEM_TIMEDWAIT */
172 
173  return retval;
174 }
175 
176 Uint32
177 SDL_SemValue(SDL_sem * sem)
178 {
179  int ret = 0;
180  if (sem) {
181  sem_getvalue(&sem->sem, &ret);
182  if (ret < 0) {
183  ret = 0;
184  }
185  }
186  return (Uint32) ret;
187 }
188 
189 int
190 SDL_SemPost(SDL_sem * sem)
191 {
192  int retval;
193 
194  if (!sem) {
195  return SDL_SetError("Passed a NULL semaphore");
196  }
197 
198  retval = sem_post(&sem->sem);
199  if (retval < 0) {
200  SDL_SetError("sem_post() failed");
201  }
202  return retval;
203 }
204 
205 #endif /* __MACOSX__ */
206 /* vi: set ts=4 sw=4 expandtab: */
GLuint GLuint end
Definition: SDL_opengl.h:1571
uint32_t Uint32
An unsigned 32-bit integer type.
Definition: SDL_stdinc.h:169
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
int SDL_SemWait(SDL_sem *sem)
Definition: SDL_syssem.c:180
void SDL_free(void *mem)
#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