1/*
2    SDL - Simple DirectMedia Layer
3    Copyright (C) 1997-2012 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#include <sys/time.h>
28
29#include "SDL_thread.h"
30#include "SDL_timer.h"
31
32/* Wrapper around POSIX 1003.1b semaphores */
33
34#ifdef __MACOSX__
35/* Mac OS X doesn't support sem_getvalue() as of version 10.4 */
36#include "../generic/SDL_syssem.c"
37#else
38
39struct SDL_semaphore {
40	sem_t sem;
41};
42
43/* Create a semaphore, initialized with value */
44SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
45{
46	SDL_sem *sem = (SDL_sem *) SDL_malloc(sizeof(SDL_sem));
47	if ( sem ) {
48		if ( sem_init(&sem->sem, 0, initial_value) < 0 ) {
49			SDL_SetError("sem_init() failed");
50			SDL_free(sem);
51			sem = NULL;
52		}
53	} else {
54		SDL_OutOfMemory();
55	}
56	return sem;
57}
58
59void SDL_DestroySemaphore(SDL_sem *sem)
60{
61	if ( sem ) {
62		sem_destroy(&sem->sem);
63		SDL_free(sem);
64	}
65}
66
67int SDL_SemTryWait(SDL_sem *sem)
68{
69	int retval;
70
71	if ( ! sem ) {
72		SDL_SetError("Passed a NULL semaphore");
73		return -1;
74	}
75	retval = SDL_MUTEX_TIMEDOUT;
76	if ( sem_trywait(&sem->sem) == 0 ) {
77		retval = 0;
78	}
79	return retval;
80}
81
82int SDL_SemWait(SDL_sem *sem)
83{
84	int retval;
85
86	if ( ! sem ) {
87		SDL_SetError("Passed a NULL semaphore");
88		return -1;
89	}
90
91	while ( ((retval = sem_wait(&sem->sem)) == -1) && (errno == EINTR) ) {}
92	if ( retval < 0 ) {
93		SDL_SetError("sem_wait() failed");
94	}
95	return retval;
96}
97
98int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
99{
100	int retval;
101#ifdef HAVE_SEM_TIMEDWAIT
102	struct timeval now;
103	struct timespec ts_timeout;
104#else
105	Uint32 end;
106#endif
107
108	if ( ! sem ) {
109		SDL_SetError("Passed a NULL semaphore");
110		return -1;
111	}
112
113	/* Try the easy cases first */
114	if ( timeout == 0 ) {
115		return SDL_SemTryWait(sem);
116	}
117	if ( timeout == SDL_MUTEX_MAXWAIT ) {
118		return SDL_SemWait(sem);
119	}
120
121#ifdef HAVE_SEM_TIMEDWAIT
122	/* Setup the timeout. sem_timedwait doesn't wait for
123	 * a lapse of time, but until we reach a certain time.
124	 * This time is now plus the timeout.
125	 */
126	gettimeofday(&now, NULL);
127
128	/* Add our timeout to current time */
129	now.tv_usec += (timeout % 1000) * 1000;
130	now.tv_sec += timeout / 1000;
131
132	/* Wrap the second if needed */
133	if ( now.tv_usec >= 1000000 ) {
134		now.tv_usec -= 1000000;
135		now.tv_sec ++;
136	}
137
138	/* Convert to timespec */
139	ts_timeout.tv_sec = now.tv_sec;
140	ts_timeout.tv_nsec = now.tv_usec * 1000;
141
142	/* Wait. */
143	do
144		retval = sem_timedwait(&sem->sem, &ts_timeout);
145	while (retval == -1 && errno == EINTR);
146
147	if (retval == -1)
148		SDL_SetError(strerror(errno));
149#else
150	end = SDL_GetTicks() + timeout;
151	while ((retval = SDL_SemTryWait(sem)) == SDL_MUTEX_TIMEDOUT) {
152		if ((SDL_GetTicks() - end) >= 0) {
153			break;
154		}
155		SDL_Delay(0);
156	}
157#endif /* HAVE_SEM_TIMEDWAIT */
158
159	return retval;
160}
161
162Uint32 SDL_SemValue(SDL_sem *sem)
163{
164	int ret = 0;
165	if ( sem ) {
166		sem_getvalue(&sem->sem, &ret);
167		if ( ret < 0 ) {
168			ret = 0;
169		}
170	}
171	return (Uint32)ret;
172}
173
174int SDL_SemPost(SDL_sem *sem)
175{
176	int retval;
177
178	if ( ! sem ) {
179		SDL_SetError("Passed a NULL semaphore");
180		return -1;
181	}
182
183	retval = sem_post(&sem->sem);
184	if ( retval < 0 ) {
185		SDL_SetError("sem_post() failed");
186	}
187	return retval;
188}
189
190#endif /* __MACOSX__ */
191