Atlas - SDL_syssem.c
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 Sam Lantinga <[email protected]>
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
39struct SDL_semaphore
40{
41    sem_t sem;
42};
43
44/* Create a semaphore, initialized with value */
45SDL_sem *
46SDL_CreateSemaphore(Uint32 initial_value)
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 {
56        SDL_OutOfMemory();
57    }
58    return sem;
59}
60
61void
62SDL_DestroySemaphore(SDL_sem * sem)
63{
64    if (sem) {
65        sem_destroy(&sem->sem);
66        SDL_free(sem);
67    }
68}
69
70int
71SDL_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
85int
86SDL_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
104int
105SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
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
179Uint32
180SDL_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
192int
193SDL_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: */
210
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