w32pthreads: Mark functions in compatibility wrapper as av_unused
[ffmpeg.git] / compat / w32pthreads.h
1 /*
2  * Copyright (C) 2010-2011 x264 project
3  *
4  * Authors: Steven Walters <kemuri9@gmail.com>
5  *          Pegasys Inc. <http://www.pegasys-inc.com>
6  *
7  * This file is part of Libav.
8  *
9  * Libav is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * Libav is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with Libav; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23
24 /**
25  * @file
26  * w32threads to pthreads wrapper
27  */
28
29 #ifndef LIBAV_COMPAT_W32PTHREADS_H
30 #define LIBAV_COMPAT_W32PTHREADS_H
31
32 /* Build up a pthread-like API using underlying Windows API. Have only static
33  * methods so as to not conflict with a potentially linked in pthread-win32
34  * library.
35  * As most functions here are used without checking return values,
36  * only implement return values as necessary. */
37
38 #define WIN32_LEAN_AND_MEAN
39 #include <windows.h>
40 #include <process.h>
41
42 #include "libavutil/attributes.h"
43 #include "libavutil/internal.h"
44 #include "libavutil/mem.h"
45
46 typedef struct pthread_t {
47     void *handle;
48     void *(*func)(void* arg);
49     void *arg;
50     void *ret;
51 } pthread_t;
52
53 /* the conditional variable api for windows 6.0+ uses critical sections and
54  * not mutexes */
55 typedef CRITICAL_SECTION pthread_mutex_t;
56
57 /* This is the CONDITIONAL_VARIABLE typedef for using Window's native
58  * conditional variables on kernels 6.0+.
59  * MinGW does not currently have this typedef. */
60 typedef struct pthread_cond_t {
61     void *ptr;
62 } pthread_cond_t;
63
64 /* function pointers to conditional variable API on windows 6.0+ kernels */
65 #if _WIN32_WINNT < 0x0600
66 static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
67 static void (WINAPI *cond_init)(pthread_cond_t *cond);
68 static void (WINAPI *cond_signal)(pthread_cond_t *cond);
69 static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
70                                 DWORD milliseconds);
71 #else
72 #define cond_init      InitializeConditionVariable
73 #define cond_broadcast WakeAllConditionVariable
74 #define cond_signal    WakeConditionVariable
75 #define cond_wait      SleepConditionVariableCS
76
77 #define CreateEvent(a, reset, init, name)                   \
78     CreateEventEx(a, name,                                  \
79                   (reset ? CREATE_EVENT_MANUAL_RESET : 0) | \
80                   (init ? CREATE_EVENT_INITIAL_SET : 0),    \
81                   EVENT_ALL_ACCESS)
82 // CreateSemaphoreExA seems to be desktop-only, but as long as we don't
83 // use named semaphores, it doesn't matter if we use the W version.
84 #define CreateSemaphore(a, b, c, d) \
85     CreateSemaphoreExW(a, b, c, d, 0, SEMAPHORE_ALL_ACCESS)
86 #define InitializeCriticalSection(x) InitializeCriticalSectionEx(x, 0, 0)
87 #define WaitForSingleObject(a, b) WaitForSingleObjectEx(a, b, FALSE)
88 #endif
89
90 static av_unused unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
91 {
92     pthread_t *h = arg;
93     h->ret = h->func(h->arg);
94     return 0;
95 }
96
97 static av_unused int pthread_create(pthread_t *thread, const void *unused_attr,
98                                     void *(*start_routine)(void*), void *arg)
99 {
100     thread->func   = start_routine;
101     thread->arg    = arg;
102     thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
103                                            0, NULL);
104     return !thread->handle;
105 }
106
107 static av_unused void pthread_join(pthread_t thread, void **value_ptr)
108 {
109     DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
110     if (ret != WAIT_OBJECT_0)
111         return;
112     if (value_ptr)
113         *value_ptr = thread.ret;
114     CloseHandle(thread.handle);
115 }
116
117 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
118 {
119     InitializeCriticalSection(m);
120     return 0;
121 }
122 static inline int pthread_mutex_destroy(pthread_mutex_t *m)
123 {
124     DeleteCriticalSection(m);
125     return 0;
126 }
127 static inline int pthread_mutex_lock(pthread_mutex_t *m)
128 {
129     EnterCriticalSection(m);
130     return 0;
131 }
132 static inline int pthread_mutex_unlock(pthread_mutex_t *m)
133 {
134     LeaveCriticalSection(m);
135     return 0;
136 }
137
138 /* for pre-Windows 6.0 platforms we need to define and use our own condition
139  * variable and api */
140 typedef struct  win32_cond_t {
141     pthread_mutex_t mtx_broadcast;
142     pthread_mutex_t mtx_waiter_count;
143     volatile int waiter_count;
144     HANDLE semaphore;
145     HANDLE waiters_done;
146     volatile int is_broadcast;
147 } win32_cond_t;
148
149 static av_unused void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
150 {
151     win32_cond_t *win32_cond = NULL;
152     if (cond_init) {
153         cond_init(cond);
154         return;
155     }
156
157     /* non native condition variables */
158     win32_cond = av_mallocz(sizeof(win32_cond_t));
159     if (!win32_cond)
160         return;
161     cond->ptr = win32_cond;
162     win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
163     if (!win32_cond->semaphore)
164         return;
165     win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
166     if (!win32_cond->waiters_done)
167         return;
168
169     pthread_mutex_init(&win32_cond->mtx_waiter_count, NULL);
170     pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
171 }
172
173 static av_unused void pthread_cond_destroy(pthread_cond_t *cond)
174 {
175     win32_cond_t *win32_cond = cond->ptr;
176     /* native condition variables do not destroy */
177     if (cond_init)
178         return;
179
180     /* non native condition variables */
181     CloseHandle(win32_cond->semaphore);
182     CloseHandle(win32_cond->waiters_done);
183     pthread_mutex_destroy(&win32_cond->mtx_waiter_count);
184     pthread_mutex_destroy(&win32_cond->mtx_broadcast);
185     av_freep(&win32_cond);
186     cond->ptr = NULL;
187 }
188
189 static av_unused void pthread_cond_broadcast(pthread_cond_t *cond)
190 {
191     win32_cond_t *win32_cond = cond->ptr;
192     int have_waiter;
193
194     if (cond_broadcast) {
195         cond_broadcast(cond);
196         return;
197     }
198
199     /* non native condition variables */
200     pthread_mutex_lock(&win32_cond->mtx_broadcast);
201     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
202     have_waiter = 0;
203
204     if (win32_cond->waiter_count) {
205         win32_cond->is_broadcast = 1;
206         have_waiter = 1;
207     }
208
209     if (have_waiter) {
210         ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
211         pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
212         WaitForSingleObject(win32_cond->waiters_done, INFINITE);
213         ResetEvent(win32_cond->waiters_done);
214         win32_cond->is_broadcast = 0;
215     } else
216         pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
217     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
218 }
219
220 static av_unused int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
221 {
222     win32_cond_t *win32_cond = cond->ptr;
223     int last_waiter;
224     if (cond_wait) {
225         cond_wait(cond, mutex, INFINITE);
226         return 0;
227     }
228
229     /* non native condition variables */
230     pthread_mutex_lock(&win32_cond->mtx_broadcast);
231     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
232     win32_cond->waiter_count++;
233     pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
234     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
235
236     // unlock the external mutex
237     pthread_mutex_unlock(mutex);
238     WaitForSingleObject(win32_cond->semaphore, INFINITE);
239
240     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
241     win32_cond->waiter_count--;
242     last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
243     pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
244
245     if (last_waiter)
246         SetEvent(win32_cond->waiters_done);
247
248     // lock the external mutex
249     return pthread_mutex_lock(mutex);
250 }
251
252 static av_unused void pthread_cond_signal(pthread_cond_t *cond)
253 {
254     win32_cond_t *win32_cond = cond->ptr;
255     int have_waiter;
256     if (cond_signal) {
257         cond_signal(cond);
258         return;
259     }
260
261     pthread_mutex_lock(&win32_cond->mtx_broadcast);
262
263     /* non-native condition variables */
264     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
265     have_waiter = win32_cond->waiter_count;
266     pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
267
268     if (have_waiter) {
269         ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
270         WaitForSingleObject(win32_cond->waiters_done, INFINITE);
271         ResetEvent(win32_cond->waiters_done);
272     }
273
274     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
275 }
276
277 static av_unused void w32thread_init(void)
278 {
279 #if _WIN32_WINNT < 0x0600
280     HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
281     /* if one is available, then they should all be available */
282     cond_init      =
283         (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
284     cond_broadcast =
285         (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
286     cond_signal    =
287         (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
288     cond_wait      =
289         (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
290 #endif
291
292 }
293
294 #endif /* LIBAV_COMPAT_W32PTHREADS_H */