FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
w32pthreads.h
Go to the documentation of this file.
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 CONDITION_VARIABLE typedef for using Windows' native
59  * conditional variables on kernels 6.0+. */
60 #if HAVE_CONDITION_VARIABLE_PTR
61 typedef CONDITION_VARIABLE pthread_cond_t;
62 #else
63 typedef struct pthread_cond_t {
64  void *Ptr;
66 #endif
67 
68 #if _WIN32_WINNT >= 0x0600
69 #define InitializeCriticalSection(x) InitializeCriticalSectionEx(x, 0, 0)
70 #define WaitForSingleObject(a, b) WaitForSingleObjectEx(a, b, FALSE)
71 #endif
72 
73 static av_unused unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
74 {
75  pthread_t *h = arg;
76  h->ret = h->func(h->arg);
77  return 0;
78 }
79 
80 static av_unused int pthread_create(pthread_t *thread, const void *unused_attr,
81  void *(*start_routine)(void*), void *arg)
82 {
83  thread->func = start_routine;
84  thread->arg = arg;
85  thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
86  0, NULL);
87  return !thread->handle;
88 }
89 
90 static av_unused void pthread_join(pthread_t thread, void **value_ptr)
91 {
92  DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
93  if (ret != WAIT_OBJECT_0)
94  return;
95  if (value_ptr)
96  *value_ptr = thread.ret;
97  CloseHandle(thread.handle);
98 }
99 
100 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
101 {
102  InitializeCriticalSection(m);
103  return 0;
104 }
106 {
107  DeleteCriticalSection(m);
108  return 0;
109 }
111 {
112  EnterCriticalSection(m);
113  return 0;
114 }
116 {
117  LeaveCriticalSection(m);
118  return 0;
119 }
120 
121 #if _WIN32_WINNT >= 0x0600
122 static inline int pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
123 {
124  InitializeConditionVariable(cond);
125  return 0;
126 }
127 
128 /* native condition variables do not destroy */
129 static inline void pthread_cond_destroy(pthread_cond_t *cond)
130 {
131  return;
132 }
133 
134 static inline void pthread_cond_broadcast(pthread_cond_t *cond)
135 {
136  WakeAllConditionVariable(cond);
137 }
138 
139 static inline int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
140 {
141  SleepConditionVariableCS(cond, mutex, INFINITE);
142  return 0;
143 }
144 
145 static inline void pthread_cond_signal(pthread_cond_t *cond)
146 {
147  WakeConditionVariable(cond);
148 }
149 
150 #else // _WIN32_WINNT < 0x0600
151 /* for pre-Windows 6.0 platforms we need to define and use our own condition
152  * variable and api */
153 typedef struct win32_cond_t {
156  volatile int waiter_count;
159  volatile int is_broadcast;
160 } win32_cond_t;
161 
162 /* function pointers to conditional variable API on windows 6.0+ kernels */
163 static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
164 static void (WINAPI *cond_init)(pthread_cond_t *cond);
165 static void (WINAPI *cond_signal)(pthread_cond_t *cond);
166 static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
168 
169 static av_unused int pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
170 {
171  win32_cond_t *win32_cond = NULL;
172  if (cond_init) {
173  cond_init(cond);
174  return 0;
175  }
176 
177  /* non native condition variables */
178  win32_cond = av_mallocz(sizeof(win32_cond_t));
179  if (!win32_cond)
180  return ENOMEM;
181  cond->Ptr = win32_cond;
182  win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
183  if (!win32_cond->semaphore)
184  return ENOMEM;
185  win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
186  if (!win32_cond->waiters_done)
187  return ENOMEM;
188 
190  pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
191  return 0;
192 }
193 
195 {
196  win32_cond_t *win32_cond = cond->Ptr;
197  /* native condition variables do not destroy */
198  if (cond_init)
199  return;
200 
201  /* non native condition variables */
202  CloseHandle(win32_cond->semaphore);
203  CloseHandle(win32_cond->waiters_done);
205  pthread_mutex_destroy(&win32_cond->mtx_broadcast);
206  av_freep(&win32_cond);
207  cond->Ptr = NULL;
208 }
209 
211 {
212  win32_cond_t *win32_cond = cond->Ptr;
213  int have_waiter;
214 
215  if (cond_broadcast) {
216  cond_broadcast(cond);
217  return;
218  }
219 
220  /* non native condition variables */
221  pthread_mutex_lock(&win32_cond->mtx_broadcast);
222  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
223  have_waiter = 0;
224 
225  if (win32_cond->waiter_count) {
226  win32_cond->is_broadcast = 1;
227  have_waiter = 1;
228  }
229 
230  if (have_waiter) {
231  ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
233  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
234  ResetEvent(win32_cond->waiters_done);
235  win32_cond->is_broadcast = 0;
236  } else
238  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
239 }
240 
242 {
243  win32_cond_t *win32_cond = cond->Ptr;
244  int last_waiter;
245  if (cond_wait) {
246  cond_wait(cond, mutex, INFINITE);
247  return 0;
248  }
249 
250  /* non native condition variables */
251  pthread_mutex_lock(&win32_cond->mtx_broadcast);
252  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
253  win32_cond->waiter_count++;
255  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
256 
257  // unlock the external mutex
258  pthread_mutex_unlock(mutex);
259  WaitForSingleObject(win32_cond->semaphore, INFINITE);
260 
261  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
262  win32_cond->waiter_count--;
263  last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
265 
266  if (last_waiter)
267  SetEvent(win32_cond->waiters_done);
268 
269  // lock the external mutex
270  return pthread_mutex_lock(mutex);
271 }
272 
274 {
275  win32_cond_t *win32_cond = cond->Ptr;
276  int have_waiter;
277  if (cond_signal) {
278  cond_signal(cond);
279  return;
280  }
281 
282  pthread_mutex_lock(&win32_cond->mtx_broadcast);
283 
284  /* non-native condition variables */
285  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
286  have_waiter = win32_cond->waiter_count;
288 
289  if (have_waiter) {
290  ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
291  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
292  ResetEvent(win32_cond->waiters_done);
293  }
294 
295  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
296 }
297 #endif
298 
299 static av_unused void w32thread_init(void)
300 {
301 #if _WIN32_WINNT < 0x0600
302  HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
303  /* if one is available, then they should all be available */
304  cond_init =
305  (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
306  cond_broadcast =
307  (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
308  cond_signal =
309  (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
310  cond_wait =
311  (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
312 #endif
313 
314 }
315 
316 #endif /* FFMPEG_COMPAT_W32PTHREADS_H */