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 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 
29 #ifndef AVCODEC_W32PTHREADS_H
30 #define AVCODEC_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 typedef struct {
43  void *handle;
44  void *(*func)(void* arg);
45  void *arg;
46  void *ret;
47 } pthread_t;
48 
49 /* the conditional variable api for windows 6.0+ uses critical sections and
50  * not mutexes */
51 typedef CRITICAL_SECTION pthread_mutex_t;
52 
53 /* This is the CONDITIONAL_VARIABLE typedef for using Window's native
54  * conditional variables on kernels 6.0+.
55  * MinGW does not currently have this typedef. */
56 typedef struct {
57  void *ptr;
59 
60 /* function pointers to conditional variable API on windows 6.0+ kernels */
61 static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
62 static void (WINAPI *cond_init)(pthread_cond_t *cond);
63 static void (WINAPI *cond_signal)(pthread_cond_t *cond);
64 static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
65  DWORD milliseconds);
66 
67 static unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
68 {
69  pthread_t *h = arg;
70  h->ret = h->func(h->arg);
71  return 0;
72 }
73 
74 static int pthread_create(pthread_t *thread, const void *unused_attr,
75  void *(*start_routine)(void*), void *arg)
76 {
77  thread->func = start_routine;
78  thread->arg = arg;
79  thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
80  0, NULL);
81  return !thread->handle;
82 }
83 
84 static void pthread_join(pthread_t thread, void **value_ptr)
85 {
86  DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
87  if (ret != WAIT_OBJECT_0)
88  return;
89  if (value_ptr)
90  *value_ptr = thread.ret;
91  CloseHandle(thread.handle);
92 }
93 
94 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
95 {
96  InitializeCriticalSection(m);
97  return 0;
98 }
100 {
101  DeleteCriticalSection(m);
102  return 0;
103 }
104 static inline int pthread_mutex_lock(pthread_mutex_t *m)
105 {
106  EnterCriticalSection(m);
107  return 0;
108 }
110 {
111  LeaveCriticalSection(m);
112  return 0;
113 }
114 
115 /* for pre-Windows 6.0 platforms we need to define and use our own condition
116  * variable and api */
117 typedef struct {
120  volatile int waiter_count;
121  HANDLE semaphore;
122  HANDLE waiters_done;
123  volatile int is_broadcast;
124 } win32_cond_t;
125 
126 static void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
127 {
128  win32_cond_t *win32_cond = NULL;
129  if (cond_init) {
130  cond_init(cond);
131  return;
132  }
133 
134  /* non native condition variables */
135  win32_cond = av_mallocz(sizeof(win32_cond_t));
136  if (!win32_cond)
137  return;
138  cond->ptr = win32_cond;
139  win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
140  if (!win32_cond->semaphore)
141  return;
142  win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
143  if (!win32_cond->waiters_done)
144  return;
145 
147  pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
148 }
149 
151 {
152  win32_cond_t *win32_cond = cond->ptr;
153  /* native condition variables do not destroy */
154  if (cond_init)
155  return;
156 
157  /* non native condition variables */
158  CloseHandle(win32_cond->semaphore);
159  CloseHandle(win32_cond->waiters_done);
161  pthread_mutex_destroy(&win32_cond->mtx_broadcast);
162  av_freep(&win32_cond);
163  cond->ptr = NULL;
164 }
165 
167 {
168  win32_cond_t *win32_cond = cond->ptr;
169  int have_waiter;
170 
171  if (cond_broadcast) {
172  cond_broadcast(cond);
173  return;
174  }
175 
176  /* non native condition variables */
177  pthread_mutex_lock(&win32_cond->mtx_broadcast);
178  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
179  have_waiter = 0;
180 
181  if (win32_cond->waiter_count) {
182  win32_cond->is_broadcast = 1;
183  have_waiter = 1;
184  }
185 
186  if (have_waiter) {
187  ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
189  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
190  ResetEvent(win32_cond->waiters_done);
191  win32_cond->is_broadcast = 0;
192  } else
194  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
195 }
196 
198 {
199  win32_cond_t *win32_cond = cond->ptr;
200  int last_waiter;
201  if (cond_wait) {
202  cond_wait(cond, mutex, INFINITE);
203  return;
204  }
205 
206  /* non native condition variables */
207  pthread_mutex_lock(&win32_cond->mtx_broadcast);
208  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
209  win32_cond->waiter_count++;
211  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
212 
213  // unlock the external mutex
214  pthread_mutex_unlock(mutex);
215  WaitForSingleObject(win32_cond->semaphore, INFINITE);
216 
217  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
218  win32_cond->waiter_count--;
219  last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
221 
222  if (last_waiter)
223  SetEvent(win32_cond->waiters_done);
224 
225  // lock the external mutex
226  return pthread_mutex_lock(mutex);
227 }
228 
230 {
231  win32_cond_t *win32_cond = cond->ptr;
232  int have_waiter;
233  if (cond_signal) {
234  cond_signal(cond);
235  return;
236  }
237 
238  pthread_mutex_lock(&win32_cond->mtx_broadcast);
239 
240  /* non-native condition variables */
241  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
242  have_waiter = win32_cond->waiter_count;
244 
245  if (have_waiter) {
246  ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
247  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
248  ResetEvent(win32_cond->waiters_done);
249  }
250 
251  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
252 }
253 
254 static void w32thread_init(void)
255 {
256  HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
257  /* if one is available, then they should all be available */
258  cond_init =
259  (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
260  cond_broadcast =
261  (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
262  cond_signal =
263  (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
264  cond_wait =
265  (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
266 }
267 
268 #endif /* AVCODEC_W32PTHREADS_H */