1 /*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2016 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 #if SDL_THREAD_WINDOWS
24
25 /* Semaphore functions using the Win32 API */
26
27 #include "../../core/windows/SDL_windows.h"
28
29 #include "SDL_thread.h"
30
31 struct SDL_semaphore
32 {
33 HANDLE id;
34 LONG count;
35 };
36
37
38 /* Create a semaphore */
39 SDL_sem *
SDL_CreateSemaphore(Uint32 initial_value)40 SDL_CreateSemaphore(Uint32 initial_value)
41 {
42 SDL_sem *sem;
43
44 /* Allocate sem memory */
45 sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
46 if (sem) {
47 /* Create the semaphore, with max value 32K */
48 #if __WINRT__
49 sem->id = CreateSemaphoreEx(NULL, initial_value, 32 * 1024, NULL, 0, SEMAPHORE_ALL_ACCESS);
50 #else
51 sem->id = CreateSemaphore(NULL, initial_value, 32 * 1024, NULL);
52 #endif
53 sem->count = initial_value;
54 if (!sem->id) {
55 SDL_SetError("Couldn't create semaphore");
56 SDL_free(sem);
57 sem = NULL;
58 }
59 } else {
60 SDL_OutOfMemory();
61 }
62 return (sem);
63 }
64
65 /* Free the semaphore */
66 void
SDL_DestroySemaphore(SDL_sem * sem)67 SDL_DestroySemaphore(SDL_sem * sem)
68 {
69 if (sem) {
70 if (sem->id) {
71 CloseHandle(sem->id);
72 sem->id = 0;
73 }
74 SDL_free(sem);
75 }
76 }
77
78 int
SDL_SemWaitTimeout(SDL_sem * sem,Uint32 timeout)79 SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
80 {
81 int retval;
82 DWORD dwMilliseconds;
83
84 if (!sem) {
85 return SDL_SetError("Passed a NULL sem");
86 }
87
88 if (timeout == SDL_MUTEX_MAXWAIT) {
89 dwMilliseconds = INFINITE;
90 } else {
91 dwMilliseconds = (DWORD) timeout;
92 }
93 #if __WINRT__
94 switch (WaitForSingleObjectEx(sem->id, dwMilliseconds, FALSE)) {
95 #else
96 switch (WaitForSingleObject(sem->id, dwMilliseconds)) {
97 #endif
98 case WAIT_OBJECT_0:
99 InterlockedDecrement(&sem->count);
100 retval = 0;
101 break;
102 case WAIT_TIMEOUT:
103 retval = SDL_MUTEX_TIMEDOUT;
104 break;
105 default:
106 retval = SDL_SetError("WaitForSingleObject() failed");
107 break;
108 }
109 return retval;
110 }
111
112 int
113 SDL_SemTryWait(SDL_sem * sem)
114 {
115 return SDL_SemWaitTimeout(sem, 0);
116 }
117
118 int
119 SDL_SemWait(SDL_sem * sem)
120 {
121 return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
122 }
123
124 /* Returns the current count of the semaphore */
125 Uint32
126 SDL_SemValue(SDL_sem * sem)
127 {
128 if (!sem) {
129 SDL_SetError("Passed a NULL sem");
130 return 0;
131 }
132 return (Uint32)sem->count;
133 }
134
135 int
136 SDL_SemPost(SDL_sem * sem)
137 {
138 if (!sem) {
139 return SDL_SetError("Passed a NULL sem");
140 }
141 /* Increase the counter in the first place, because
142 * after a successful release the semaphore may
143 * immediately get destroyed by another thread which
144 * is waiting for this semaphore.
145 */
146 InterlockedIncrement(&sem->count);
147 if (ReleaseSemaphore(sem->id, 1, NULL) == FALSE) {
148 InterlockedDecrement(&sem->count); /* restore */
149 return SDL_SetError("ReleaseSemaphore() failed");
150 }
151 return 0;
152 }
153
154 #endif /* SDL_THREAD_WINDOWS */
155
156 /* vi: set ts=4 sw=4 expandtab: */
157