1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2025 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// Wrapper around POSIX 1003.1b semaphores
30
31#if defined(SDL_PLATFORM_MACOS) || defined(SDL_PLATFORM_IOS)
32// macOS doesn't support sem_getvalue() as of version 10.4
33#include "../generic/SDL_syssem.c"
34#else
35
36struct SDL_Semaphore
37{
38 sem_t sem;
39};
40
41// Create a semaphore, initialized with value
42SDL_Semaphore *SDL_CreateSemaphore(Uint32 initial_value)
43{
44 SDL_Semaphore *sem = (SDL_Semaphore *)SDL_malloc(sizeof(SDL_Semaphore));
45 if (sem) {
46 if (sem_init(&sem->sem, 0, initial_value) < 0) {
47 SDL_SetError("sem_init() failed");
48 SDL_free(sem);
49 sem = NULL;
50 }
51 }
52 return sem;
53}
54
55void SDL_DestroySemaphore(SDL_Semaphore *sem)
56{
57 if (sem) {
58 sem_destroy(&sem->sem);
59 SDL_free(sem);
60 }
61}
62
63bool SDL_WaitSemaphoreTimeoutNS(SDL_Semaphore *sem, Sint64 timeoutNS)
64{
65#ifdef HAVE_SEM_TIMEDWAIT
66#ifndef HAVE_CLOCK_GETTIME
67 struct timeval now;
68#endif
69 struct timespec ts_timeout;
70#else
71 Uint64 stop_time;
72#endif
73
74 if (!sem) {
75 return true;
76 }
77
78 // Try the easy cases first
79 if (timeoutNS == 0) {
80 return (sem_trywait(&sem->sem) == 0);
81 }
82
83 if (timeoutNS < 0) {
84 int rc;
85 do {
86 rc = sem_wait(&sem->sem);
87 } while (rc < 0 && errno == EINTR);
88
89 return (rc == 0);
90 }
91
92#ifdef HAVE_SEM_TIMEDWAIT
93 /* Setup the timeout. sem_timedwait doesn't wait for
94 * a lapse of time, but until we reach a certain time.
95 * This time is now plus the timeout.
96 */
97#ifdef HAVE_CLOCK_GETTIME
98 clock_gettime(CLOCK_REALTIME, &ts_timeout);
99
100 // Add our timeout to current time
101 ts_timeout.tv_sec += (timeoutNS / SDL_NS_PER_SECOND);
102 ts_timeout.tv_nsec += (timeoutNS % SDL_NS_PER_SECOND);
103#else
104 gettimeofday(&now, NULL);
105
106 // Add our timeout to current time
107 ts_timeout.tv_sec = now.tv_sec + (timeoutNS / SDL_NS_PER_SECOND);
108 ts_timeout.tv_nsec = SDL_US_TO_NS(now.tv_usec) + (timeoutNS % SDL_NS_PER_SECOND);
109#endif
110
111 // Wrap the second if needed
112 while (ts_timeout.tv_nsec >= 1000000000) {
113 ts_timeout.tv_sec += 1;
114 ts_timeout.tv_nsec -= 1000000000;
115 }
116
117 // Wait.
118 int rc;
119 do {
120 rc = sem_timedwait(&sem->sem, &ts_timeout);
121 } while (rc < 0 && errno == EINTR);
122
123 return (rc == 0);
124#else
125 stop_time = SDL_GetTicksNS() + timeoutNS;
126 while (sem_trywait(&sem->sem) != 0) {
127 if (SDL_GetTicksNS() >= stop_time) {
128 return false;
129 }
130 SDL_DelayNS(100);
131 }
132 return true;
133#endif // HAVE_SEM_TIMEDWAIT
134}
135
136Uint32 SDL_GetSemaphoreValue(SDL_Semaphore *sem)
137{
138 int ret = 0;
139
140 if (!sem) {
141 return 0;
142 }
143
144 sem_getvalue(&sem->sem, &ret);
145 if (ret < 0) {
146 ret = 0;
147 }
148 return (Uint32)ret;
149}
150
151void SDL_SignalSemaphore(SDL_Semaphore *sem)
152{
153 if (!sem) {
154 return;
155 }
156
157 sem_post(&sem->sem);
158}
159
160#endif // SDL_PLATFORM_MACOS
161