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w32pthreads.h
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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 FFmpeg.
8  *
9  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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 FFMPEG_COMPAT_W32PTHREADS_H
30 #define FFMPEG_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/common.h"
44 #include "libavutil/internal.h"
45 #include "libavutil/mem.h"
46 
47 typedef struct pthread_t {
48  void *handle;
49  void *(*func)(void* arg);
50  void *arg;
51  void *ret;
52 } pthread_t;
53 
54 /* the conditional variable api for windows 6.0+ uses critical sections and
55  * not mutexes */
56 typedef CRITICAL_SECTION pthread_mutex_t;
57 
58 /* This is the CONDITIONAL_VARIABLE typedef for using Window's native
59  * conditional variables on kernels 6.0+.
60  * MinGW does not currently have this typedef. */
61 typedef struct pthread_cond_t {
62  void *ptr;
64 
65 /* function pointers to conditional variable API on windows 6.0+ kernels */
66 #if _WIN32_WINNT < 0x0600
67 static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
68 static void (WINAPI *cond_init)(pthread_cond_t *cond);
69 static void (WINAPI *cond_signal)(pthread_cond_t *cond);
70 static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
72 #else
73 #define cond_init InitializeConditionVariable
74 #define cond_broadcast WakeAllConditionVariable
75 #define cond_signal WakeConditionVariable
76 #define cond_wait SleepConditionVariableCS
77 
78 #define CreateEvent(a, reset, init, name) \
79  CreateEventEx(a, name, \
80  (reset ? CREATE_EVENT_MANUAL_RESET : 0) | \
81  (init ? CREATE_EVENT_INITIAL_SET : 0), \
82  EVENT_ALL_ACCESS)
83 // CreateSemaphoreExA seems to be desktop-only, but as long as we don't
84 // use named semaphores, it doesn't matter if we use the W version.
85 #define CreateSemaphore(a, b, c, d) \
86  CreateSemaphoreExW(a, b, c, d, 0, SEMAPHORE_ALL_ACCESS)
87 #define InitializeCriticalSection(x) InitializeCriticalSectionEx(x, 0, 0)
88 #define WaitForSingleObject(a, b) WaitForSingleObjectEx(a, b, FALSE)
89 #endif
90 
91 static av_unused unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
92 {
93  pthread_t *h = arg;
94  h->ret = h->func(h->arg);
95  return 0;
96 }
97 
98 static av_unused int pthread_create(pthread_t *thread, const void *unused_attr,
99  void *(*start_routine)(void*), void *arg)
100 {
101  thread->func = start_routine;
102  thread->arg = arg;
103  thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
104  0, NULL);
105  return !thread->handle;
106 }
107 
108 static av_unused void pthread_join(pthread_t thread, void **value_ptr)
109 {
110  DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
111  if (ret != WAIT_OBJECT_0)
112  return;
113  if (value_ptr)
114  *value_ptr = thread.ret;
115  CloseHandle(thread.handle);
116 }
117 
118 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
119 {
120  InitializeCriticalSection(m);
121  return 0;
122 }
124 {
125  DeleteCriticalSection(m);
126  return 0;
127 }
129 {
130  EnterCriticalSection(m);
131  return 0;
132 }
134 {
135  LeaveCriticalSection(m);
136  return 0;
137 }
138 
139 /* for pre-Windows 6.0 platforms we need to define and use our own condition
140  * variable and api */
141 typedef struct win32_cond_t {
144  volatile int waiter_count;
147  volatile int is_broadcast;
148 } win32_cond_t;
149 
150 static av_unused int pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
151 {
152  win32_cond_t *win32_cond = NULL;
153  if (cond_init) {
154  cond_init(cond);
155  return 0;
156  }
157 
158  /* non native condition variables */
159  win32_cond = av_mallocz(sizeof(win32_cond_t));
160  if (!win32_cond)
161  return ENOMEM;
162  cond->ptr = win32_cond;
163  win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
164  if (!win32_cond->semaphore)
165  return ENOMEM;
166  win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
167  if (!win32_cond->waiters_done)
168  return ENOMEM;
169 
170  pthread_mutex_init(&win32_cond->mtx_waiter_count, NULL);
171  pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
172  return 0;
173 }
174 
176 {
177  win32_cond_t *win32_cond = cond->ptr;
178  /* native condition variables do not destroy */
179  if (cond_init)
180  return;
181 
182  /* non native condition variables */
183  CloseHandle(win32_cond->semaphore);
184  CloseHandle(win32_cond->waiters_done);
186  pthread_mutex_destroy(&win32_cond->mtx_broadcast);
187  av_freep(&win32_cond);
188  cond->ptr = NULL;
189 }
190 
192 {
193  win32_cond_t *win32_cond = cond->ptr;
194  int have_waiter;
195 
196  if (cond_broadcast) {
197  cond_broadcast(cond);
198  return;
199  }
200 
201  /* non native condition variables */
202  pthread_mutex_lock(&win32_cond->mtx_broadcast);
203  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
204  have_waiter = 0;
205 
206  if (win32_cond->waiter_count) {
207  win32_cond->is_broadcast = 1;
208  have_waiter = 1;
209  }
210 
211  if (have_waiter) {
212  ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
214  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
215  ResetEvent(win32_cond->waiters_done);
216  win32_cond->is_broadcast = 0;
217  } else
219  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
220 }
221 
223 {
224  win32_cond_t *win32_cond = cond->ptr;
225  int last_waiter;
226  if (cond_wait) {
227  cond_wait(cond, mutex, INFINITE);
228  return 0;
229  }
230 
231  /* non native condition variables */
232  pthread_mutex_lock(&win32_cond->mtx_broadcast);
233  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
234  win32_cond->waiter_count++;
236  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
237 
238  // unlock the external mutex
239  pthread_mutex_unlock(mutex);
240  WaitForSingleObject(win32_cond->semaphore, INFINITE);
241 
242  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
243  win32_cond->waiter_count--;
244  last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
246 
247  if (last_waiter)
248  SetEvent(win32_cond->waiters_done);
249 
250  // lock the external mutex
251  return pthread_mutex_lock(mutex);
252 }
253 
255 {
256  win32_cond_t *win32_cond = cond->ptr;
257  int have_waiter;
258  if (cond_signal) {
259  cond_signal(cond);
260  return;
261  }
262 
263  pthread_mutex_lock(&win32_cond->mtx_broadcast);
264 
265  /* non-native condition variables */
266  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
267  have_waiter = win32_cond->waiter_count;
269 
270  if (have_waiter) {
271  ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
272  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
273  ResetEvent(win32_cond->waiters_done);
274  }
275 
276  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
277 }
278 
279 static av_unused void w32thread_init(void)
280 {
281 #if _WIN32_WINNT < 0x0600
282  HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
283  /* if one is available, then they should all be available */
284  cond_init =
285  (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
286  cond_broadcast =
287  (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
288  cond_signal =
289  (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
290  cond_wait =
291  (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
292 #endif
293 
294 }
295 
296 #endif /* FFMPEG_COMPAT_W32PTHREADS_H */