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 #include "libavutil/internal.h"
43 #include "libavutil/mem.h"
44 
45 typedef struct pthread_t {
46  void *handle;
47  void *(*func)(void* arg);
48  void *arg;
49  void *ret;
50 } pthread_t;
51 
52 /* the conditional variable api for windows 6.0+ uses critical sections and
53  * not mutexes */
54 typedef CRITICAL_SECTION pthread_mutex_t;
55 
56 /* This is the CONDITIONAL_VARIABLE typedef for using Window's native
57  * conditional variables on kernels 6.0+.
58  * MinGW does not currently have this typedef. */
59 typedef struct pthread_cond_t {
60  void *ptr;
62 
63 /* function pointers to conditional variable API on windows 6.0+ kernels */
64 static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
65 static void (WINAPI *cond_init)(pthread_cond_t *cond);
66 static void (WINAPI *cond_signal)(pthread_cond_t *cond);
67 static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
68  DWORD milliseconds);
69 
70 static unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
71 {
72  pthread_t *h = arg;
73  h->ret = h->func(h->arg);
74  return 0;
75 }
76 
77 static int pthread_create(pthread_t *thread, const void *unused_attr,
78  void *(*start_routine)(void*), void *arg)
79 {
80  thread->func = start_routine;
81  thread->arg = arg;
82  thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
83  0, NULL);
84  return !thread->handle;
85 }
86 
87 static void pthread_join(pthread_t thread, void **value_ptr)
88 {
89  DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
90  if (ret != WAIT_OBJECT_0)
91  return;
92  if (value_ptr)
93  *value_ptr = thread.ret;
94  CloseHandle(thread.handle);
95 }
96 
97 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
98 {
99  InitializeCriticalSection(m);
100  return 0;
101 }
103 {
104  DeleteCriticalSection(m);
105  return 0;
106 }
107 static inline int pthread_mutex_lock(pthread_mutex_t *m)
108 {
109  EnterCriticalSection(m);
110  return 0;
111 }
113 {
114  LeaveCriticalSection(m);
115  return 0;
116 }
117 
118 /* for pre-Windows 6.0 platforms we need to define and use our own condition
119  * variable and api */
120 typedef struct win32_cond_t {
123  volatile int waiter_count;
124  HANDLE semaphore;
125  HANDLE waiters_done;
126  volatile int is_broadcast;
127 } win32_cond_t;
128 
129 static void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
130 {
131  win32_cond_t *win32_cond = NULL;
132  if (cond_init) {
133  cond_init(cond);
134  return;
135  }
136 
137  /* non native condition variables */
138  win32_cond = av_mallocz(sizeof(win32_cond_t));
139  if (!win32_cond)
140  return;
141  cond->ptr = win32_cond;
142  win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
143  if (!win32_cond->semaphore)
144  return;
145  win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
146  if (!win32_cond->waiters_done)
147  return;
148 
150  pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
151 }
152 
154 {
155  win32_cond_t *win32_cond = cond->ptr;
156  /* native condition variables do not destroy */
157  if (cond_init)
158  return;
159 
160  /* non native condition variables */
161  CloseHandle(win32_cond->semaphore);
162  CloseHandle(win32_cond->waiters_done);
164  pthread_mutex_destroy(&win32_cond->mtx_broadcast);
165  av_freep(&win32_cond);
166  cond->ptr = NULL;
167 }
168 
170 {
171  win32_cond_t *win32_cond = cond->ptr;
172  int have_waiter;
173 
174  if (cond_broadcast) {
175  cond_broadcast(cond);
176  return;
177  }
178 
179  /* non native condition variables */
180  pthread_mutex_lock(&win32_cond->mtx_broadcast);
181  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
182  have_waiter = 0;
183 
184  if (win32_cond->waiter_count) {
185  win32_cond->is_broadcast = 1;
186  have_waiter = 1;
187  }
188 
189  if (have_waiter) {
190  ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
192  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
193  ResetEvent(win32_cond->waiters_done);
194  win32_cond->is_broadcast = 0;
195  } else
197  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
198 }
199 
201 {
202  win32_cond_t *win32_cond = cond->ptr;
203  int last_waiter;
204  if (cond_wait) {
205  cond_wait(cond, mutex, INFINITE);
206  return 0;
207  }
208 
209  /* non native condition variables */
210  pthread_mutex_lock(&win32_cond->mtx_broadcast);
211  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
212  win32_cond->waiter_count++;
214  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
215 
216  // unlock the external mutex
217  pthread_mutex_unlock(mutex);
218  WaitForSingleObject(win32_cond->semaphore, INFINITE);
219 
220  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
221  win32_cond->waiter_count--;
222  last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
224 
225  if (last_waiter)
226  SetEvent(win32_cond->waiters_done);
227 
228  // lock the external mutex
229  return pthread_mutex_lock(mutex);
230 }
231 
233 {
234  win32_cond_t *win32_cond = cond->ptr;
235  int have_waiter;
236  if (cond_signal) {
237  cond_signal(cond);
238  return;
239  }
240 
241  pthread_mutex_lock(&win32_cond->mtx_broadcast);
242 
243  /* non-native condition variables */
244  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
245  have_waiter = win32_cond->waiter_count;
247 
248  if (have_waiter) {
249  ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
250  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
251  ResetEvent(win32_cond->waiters_done);
252  }
253 
254  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
255 }
256 
257 static void w32thread_init(void)
258 {
259  HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
260  /* if one is available, then they should all be available */
261  cond_init =
262  (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
263  cond_broadcast =
264  (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
265  cond_signal =
266  (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
267  cond_wait =
268  (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
269 }
270 
271 #endif /* AVCODEC_W32PTHREADS_H */