1 /*
2 SDL - Simple DirectMedia Layer
3 Copyright (C) 1997-2006 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 #include <pthread.h>
25 #include <semaphore.h>
26 #include <errno.h>
27
28 #include "SDL_thread.h"
29 #include "SDL_timer.h"
30
31 /* Wrapper around POSIX 1003.1b semaphores */
32
33 #ifdef __MACOSX__
34 /* Mac OS X doesn't support sem_getvalue() as of version 10.4 */
35 #include "../generic/SDL_syssem.c"
36 #else
37
38 struct SDL_semaphore {
39 sem_t sem;
40 };
41
42 /* Create a semaphore, initialized with value */
SDL_CreateSemaphore(Uint32 initial_value)43 SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
44 {
45 SDL_sem *sem = (SDL_sem *) SDL_malloc(sizeof(SDL_sem));
46 if ( sem ) {
47 if ( sem_init(&sem->sem, 0, initial_value) < 0 ) {
48 SDL_SetError("sem_init() failed");
49 SDL_free(sem);
50 sem = NULL;
51 }
52 } else {
53 SDL_OutOfMemory();
54 }
55 return sem;
56 }
57
SDL_DestroySemaphore(SDL_sem * sem)58 void SDL_DestroySemaphore(SDL_sem *sem)
59 {
60 if ( sem ) {
61 sem_destroy(&sem->sem);
62 SDL_free(sem);
63 }
64 }
65
SDL_SemTryWait(SDL_sem * sem)66 int SDL_SemTryWait(SDL_sem *sem)
67 {
68 int retval;
69
70 if ( ! sem ) {
71 SDL_SetError("Passed a NULL semaphore");
72 return -1;
73 }
74 retval = SDL_MUTEX_TIMEDOUT;
75 if ( sem_trywait(&sem->sem) == 0 ) {
76 retval = 0;
77 }
78 return retval;
79 }
80
SDL_SemWait(SDL_sem * sem)81 int SDL_SemWait(SDL_sem *sem)
82 {
83 int retval;
84
85 if ( ! sem ) {
86 SDL_SetError("Passed a NULL semaphore");
87 return -1;
88 }
89
90 while ( ((retval = sem_wait(&sem->sem)) == -1) && (errno == EINTR) ) {}
91 if ( retval < 0 ) {
92 SDL_SetError("sem_wait() failed");
93 }
94 return retval;
95 }
96
SDL_SemWaitTimeout(SDL_sem * sem,Uint32 timeout)97 int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
98 {
99 int retval;
100
101 if ( ! sem ) {
102 SDL_SetError("Passed a NULL semaphore");
103 return -1;
104 }
105
106 /* Try the easy cases first */
107 if ( timeout == 0 ) {
108 return SDL_SemTryWait(sem);
109 }
110 if ( timeout == SDL_MUTEX_MAXWAIT ) {
111 return SDL_SemWait(sem);
112 }
113
114 /* Ack! We have to busy wait... */
115 /* FIXME: Use sem_timedwait()? */
116 timeout += SDL_GetTicks();
117 do {
118 retval = SDL_SemTryWait(sem);
119 if ( retval == 0 ) {
120 break;
121 }
122 SDL_Delay(1);
123 } while ( SDL_GetTicks() < timeout );
124
125 return retval;
126 }
127
SDL_SemValue(SDL_sem * sem)128 Uint32 SDL_SemValue(SDL_sem *sem)
129 {
130 int ret = 0;
131 if ( sem ) {
132 sem_getvalue(&sem->sem, &ret);
133 if ( ret < 0 ) {
134 ret = 0;
135 }
136 }
137 return (Uint32)ret;
138 }
139
SDL_SemPost(SDL_sem * sem)140 int SDL_SemPost(SDL_sem *sem)
141 {
142 int retval;
143
144 if ( ! sem ) {
145 SDL_SetError("Passed a NULL semaphore");
146 return -1;
147 }
148
149 retval = sem_post(&sem->sem);
150 if ( retval < 0 ) {
151 SDL_SetError("sem_post() failed");
152 }
153 return retval;
154 }
155
156 #endif /* __MACOSX__ */
157