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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 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 
24 /**
25  * @file
26  * w32threads to pthreads wrapper
27  */
28 
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/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 static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
66 static void (WINAPI *cond_init)(pthread_cond_t *cond);
67 static void (WINAPI *cond_signal)(pthread_cond_t *cond);
68 static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
69  DWORD milliseconds);
70 
71 static unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
72 {
73  pthread_t *h = arg;
74  h->ret = h->func(h->arg);
75  return 0;
76 }
77 
78 static int pthread_create(pthread_t *thread, const void *unused_attr,
79  void *(*start_routine)(void*), void *arg)
80 {
81  thread->func = start_routine;
82  thread->arg = arg;
83  thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
84  0, NULL);
85  return !thread->handle;
86 }
87 
88 static void pthread_join(pthread_t thread, void **value_ptr)
89 {
90  DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
91  if (ret != WAIT_OBJECT_0)
92  return;
93  if (value_ptr)
94  *value_ptr = thread.ret;
95  CloseHandle(thread.handle);
96 }
97 
98 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
99 {
100  InitializeCriticalSection(m);
101  return 0;
102 }
104 {
105  DeleteCriticalSection(m);
106  return 0;
107 }
109 {
110  EnterCriticalSection(m);
111  return 0;
112 }
114 {
115  LeaveCriticalSection(m);
116  return 0;
117 }
118 
119 /* for pre-Windows 6.0 platforms we need to define and use our own condition
120  * variable and api */
121 typedef struct win32_cond_t {
124  volatile int waiter_count;
125  HANDLE semaphore;
126  HANDLE waiters_done;
127  volatile int is_broadcast;
128 } win32_cond_t;
129 
130 static void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
131 {
132  win32_cond_t *win32_cond = NULL;
133  if (cond_init) {
134  cond_init(cond);
135  return;
136  }
137 
138  /* non native condition variables */
139  win32_cond = av_mallocz(sizeof(win32_cond_t));
140  if (!win32_cond)
141  return;
142  cond->ptr = win32_cond;
143  win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
144  if (!win32_cond->semaphore)
145  return;
146  win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
147  if (!win32_cond->waiters_done)
148  return;
149 
151  pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
152 }
153 
155 {
156  win32_cond_t *win32_cond = cond->ptr;
157  /* native condition variables do not destroy */
158  if (cond_init)
159  return;
160 
161  /* non native condition variables */
162  CloseHandle(win32_cond->semaphore);
163  CloseHandle(win32_cond->waiters_done);
165  pthread_mutex_destroy(&win32_cond->mtx_broadcast);
166  av_freep(&win32_cond);
167  cond->ptr = NULL;
168 }
169 
171 {
172  win32_cond_t *win32_cond = cond->ptr;
173  int have_waiter;
174 
175  if (cond_broadcast) {
176  cond_broadcast(cond);
177  return;
178  }
179 
180  /* non native condition variables */
181  pthread_mutex_lock(&win32_cond->mtx_broadcast);
182  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
183  have_waiter = 0;
184 
185  if (win32_cond->waiter_count) {
186  win32_cond->is_broadcast = 1;
187  have_waiter = 1;
188  }
189 
190  if (have_waiter) {
191  ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
193  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
194  ResetEvent(win32_cond->waiters_done);
195  win32_cond->is_broadcast = 0;
196  } else
198  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
199 }
200 
202 {
203  win32_cond_t *win32_cond = cond->ptr;
204  int last_waiter;
205  if (cond_wait) {
206  cond_wait(cond, mutex, INFINITE);
207  return 0;
208  }
209 
210  /* non native condition variables */
211  pthread_mutex_lock(&win32_cond->mtx_broadcast);
212  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
213  win32_cond->waiter_count++;
215  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
216 
217  // unlock the external mutex
218  pthread_mutex_unlock(mutex);
219  WaitForSingleObject(win32_cond->semaphore, INFINITE);
220 
221  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
222  win32_cond->waiter_count--;
223  last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
225 
226  if (last_waiter)
227  SetEvent(win32_cond->waiters_done);
228 
229  // lock the external mutex
230  return pthread_mutex_lock(mutex);
231 }
232 
234 {
235  win32_cond_t *win32_cond = cond->ptr;
236  int have_waiter;
237  if (cond_signal) {
238  cond_signal(cond);
239  return;
240  }
241 
242  pthread_mutex_lock(&win32_cond->mtx_broadcast);
243 
244  /* non-native condition variables */
245  pthread_mutex_lock(&win32_cond->mtx_waiter_count);
246  have_waiter = win32_cond->waiter_count;
248 
249  if (have_waiter) {
250  ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
251  WaitForSingleObject(win32_cond->waiters_done, INFINITE);
252  ResetEvent(win32_cond->waiters_done);
253  }
254 
255  pthread_mutex_unlock(&win32_cond->mtx_broadcast);
256 }
257 
258 static void w32thread_init(void)
259 {
260  HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
261  /* if one is available, then they should all be available */
262  cond_init =
263  (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
264  cond_broadcast =
265  (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
266  cond_signal =
267  (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
268  cond_wait =
269  (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
270 }
271 
272 #endif /* AVCODEC_W32PTHREADS_H */