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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/common.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;
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,
71 #else
72 #define cond_init InitializeConditionVariable
73 #define cond_broadcast WakeAllConditionVariable
74 #define cond_signal WakeConditionVariable
75 #define cond_wait SleepConditionVariableCS
76 #endif
77 
78 static unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
79 {
80  pthread_t *h = arg;
81  h->ret = h->func(h->arg);
82  return 0;
83 }
84 
85 static int pthread_create(pthread_t *thread, const void *unused_attr,
86  void *(*start_routine)(void*), void *arg)
87 {
88  thread->func = start_routine;
89  thread->arg = arg;
90  thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
91  0, NULL);
92  return !thread->handle;
93 }
94 
95 static void pthread_join(pthread_t thread, void **value_ptr)
96 {
97  DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
98  if (ret != WAIT_OBJECT_0)
99  return;
100  if (value_ptr)
101  *value_ptr = thread.ret;
102  CloseHandle(thread.handle);
103 }
104 
105 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
106 {
107  InitializeCriticalSection(m);
108  return 0;
109 }
111 {
112  DeleteCriticalSection(m);
113  return 0;
114 }
116 {
117  EnterCriticalSection(m);
118  return 0;
119 }
121 {
122  LeaveCriticalSection(m);
123  return 0;
124 }
125 
126 /* for pre-Windows 6.0 platforms we need to define and use our own condition
127  * variable and api */
128 typedef struct win32_cond_t {
131  volatile int waiter_count;
134  volatile int is_broadcast;
135 } win32_cond_t;
136 
137 static void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
138 {
139  win32_cond_t *win32_cond = NULL;
140  if (cond_init) {
141  cond_init(cond);
142  return;
143  }
144 
145  /* non native condition variables */
146  win32_cond = av_mallocz(sizeof(win32_cond_t));
147  if (!win32_cond)
148  return;
149  cond->ptr = win32_cond;
150  win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
151  if (!win32_cond->semaphore)
152  return;
153  win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
154  if (!win32_cond->waiters_done)
155  return;
156 
157  pthread_mutex_init(&win32_cond->mtx_waiter_count, NULL);
158  pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
159 }
160 
162 {
163  win32_cond_t *win32_cond = cond->ptr;
164  /* native condition variables do not destroy */
165  if (cond_init)
166  return;
167 
168  /* non native condition variables */
169  CloseHandle(win32_cond->semaphore);
170  CloseHandle(win32_cond->waiters_done);
172  pthread_mutex_destroy(&win32_cond->mtx_broadcast);
173  av_freep(&win32_cond);
174  cond->ptr = NULL;
175 }
176 
178 {
179  win32_cond_t *win32_cond = cond->ptr;
180  int have_waiter;
181 
182  if (cond_broadcast) {
183  cond_broadcast(cond);
184  return;
185  }
186 
187  /* non native condition variables */
188  pthread_mutex_lock(&win32_cond->mtx_broadcast);
189  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
190  have_waiter = 0;
191 
192  if (win32_cond->waiter_count) {
193  win32_cond->is_broadcast = 1;
194  have_waiter = 1;
195  }
196 
197  if (have_waiter) {
198  ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
200  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
201  ResetEvent(win32_cond->waiters_done);
202  win32_cond->is_broadcast = 0;
203  } else
205  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
206 }
207 
209 {
210  win32_cond_t *win32_cond = cond->ptr;
211  int last_waiter;
212  if (cond_wait) {
213  cond_wait(cond, mutex, INFINITE);
214  return 0;
215  }
216 
217  /* non native condition variables */
218  pthread_mutex_lock(&win32_cond->mtx_broadcast);
219  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
220  win32_cond->waiter_count++;
222  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
223 
224  // unlock the external mutex
225  pthread_mutex_unlock(mutex);
226  WaitForSingleObject(win32_cond->semaphore, INFINITE);
227 
228  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
229  win32_cond->waiter_count--;
230  last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
232 
233  if (last_waiter)
234  SetEvent(win32_cond->waiters_done);
235 
236  // lock the external mutex
237  return pthread_mutex_lock(mutex);
238 }
239 
241 {
242  win32_cond_t *win32_cond = cond->ptr;
243  int have_waiter;
244  if (cond_signal) {
245  cond_signal(cond);
246  return;
247  }
248 
249  pthread_mutex_lock(&win32_cond->mtx_broadcast);
250 
251  /* non-native condition variables */
252  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
253  have_waiter = win32_cond->waiter_count;
255 
256  if (have_waiter) {
257  ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
258  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
259  ResetEvent(win32_cond->waiters_done);
260  }
261 
262  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
263 }
264 
265 static void w32thread_init(void)
266 {
267 #if _WIN32_WINNT < 0x0600
268  HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
269  /* if one is available, then they should all be available */
270  cond_init =
271  (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
272  cond_broadcast =
273  (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
274  cond_signal =
275  (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
276  cond_wait =
277  (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
278 #endif
279 
280 }
281 
282 #endif /* FFMPEG_COMPAT_W32PTHREADS_H */