Revert "w32pthread: help compiler figure out undeeded code"
[ffmpeg.git] / compat / w32pthreads.h
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 LIBAV_COMPAT_W32PTHREADS_H
30 #define LIBAV_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/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;
61 } pthread_cond_t;
62
63 /* function pointers to conditional variable API on windows 6.0+ kernels */
64 #if _WIN32_WINNT < 0x0600
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 #else
71 #define cond_init      InitializeConditionVariable
72 #define cond_broadcast WakeAllConditionVariable
73 #define cond_signal    WakeConditionVariable
74 #define cond_wait      SleepConditionVariableCS
75 #endif
76
77 static unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
78 {
79     pthread_t *h = arg;
80     h->ret = h->func(h->arg);
81     return 0;
82 }
83
84 static int pthread_create(pthread_t *thread, const void *unused_attr,
85                           void *(*start_routine)(void*), void *arg)
86 {
87     thread->func   = start_routine;
88     thread->arg    = arg;
89     thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
90                                            0, NULL);
91     return !thread->handle;
92 }
93
94 static void pthread_join(pthread_t thread, void **value_ptr)
95 {
96     DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
97     if (ret != WAIT_OBJECT_0)
98         return;
99     if (value_ptr)
100         *value_ptr = thread.ret;
101     CloseHandle(thread.handle);
102 }
103
104 static inline int pthread_mutex_init(pthread_mutex_t *m, void* attr)
105 {
106     InitializeCriticalSection(m);
107     return 0;
108 }
109 static inline int pthread_mutex_destroy(pthread_mutex_t *m)
110 {
111     DeleteCriticalSection(m);
112     return 0;
113 }
114 static inline int pthread_mutex_lock(pthread_mutex_t *m)
115 {
116     EnterCriticalSection(m);
117     return 0;
118 }
119 static inline int pthread_mutex_unlock(pthread_mutex_t *m)
120 {
121     LeaveCriticalSection(m);
122     return 0;
123 }
124
125 /* for pre-Windows 6.0 platforms we need to define and use our own condition
126  * variable and api */
127 typedef struct  win32_cond_t {
128     pthread_mutex_t mtx_broadcast;
129     pthread_mutex_t mtx_waiter_count;
130     volatile int waiter_count;
131     HANDLE semaphore;
132     HANDLE waiters_done;
133     volatile int is_broadcast;
134 } win32_cond_t;
135
136 static void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
137 {
138     win32_cond_t *win32_cond = NULL;
139     if (cond_init) {
140         cond_init(cond);
141         return;
142     }
143
144     /* non native condition variables */
145     win32_cond = av_mallocz(sizeof(win32_cond_t));
146     if (!win32_cond)
147         return;
148     cond->ptr = win32_cond;
149     win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
150     if (!win32_cond->semaphore)
151         return;
152     win32_cond->waiters_done = CreateEvent(NULL, TRUE, FALSE, NULL);
153     if (!win32_cond->waiters_done)
154         return;
155
156     pthread_mutex_init(&win32_cond->mtx_waiter_count, NULL);
157     pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
158 }
159
160 static void pthread_cond_destroy(pthread_cond_t *cond)
161 {
162     win32_cond_t *win32_cond = cond->ptr;
163     /* native condition variables do not destroy */
164     if (cond_init)
165         return;
166
167     /* non native condition variables */
168     CloseHandle(win32_cond->semaphore);
169     CloseHandle(win32_cond->waiters_done);
170     pthread_mutex_destroy(&win32_cond->mtx_waiter_count);
171     pthread_mutex_destroy(&win32_cond->mtx_broadcast);
172     av_freep(&win32_cond);
173     cond->ptr = NULL;
174 }
175
176 static void pthread_cond_broadcast(pthread_cond_t *cond)
177 {
178     win32_cond_t *win32_cond = cond->ptr;
179     int have_waiter;
180
181     if (cond_broadcast) {
182         cond_broadcast(cond);
183         return;
184     }
185
186     /* non native condition variables */
187     pthread_mutex_lock(&win32_cond->mtx_broadcast);
188     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
189     have_waiter = 0;
190
191     if (win32_cond->waiter_count) {
192         win32_cond->is_broadcast = 1;
193         have_waiter = 1;
194     }
195
196     if (have_waiter) {
197         ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
198         pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
199         WaitForSingleObject(win32_cond->waiters_done, INFINITE);
200         ResetEvent(win32_cond->waiters_done);
201         win32_cond->is_broadcast = 0;
202     } else
203         pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
204     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
205 }
206
207 static int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
208 {
209     win32_cond_t *win32_cond = cond->ptr;
210     int last_waiter;
211     if (cond_wait) {
212         cond_wait(cond, mutex, INFINITE);
213         return 0;
214     }
215
216     /* non native condition variables */
217     pthread_mutex_lock(&win32_cond->mtx_broadcast);
218     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
219     win32_cond->waiter_count++;
220     pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
221     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
222
223     // unlock the external mutex
224     pthread_mutex_unlock(mutex);
225     WaitForSingleObject(win32_cond->semaphore, INFINITE);
226
227     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
228     win32_cond->waiter_count--;
229     last_waiter = !win32_cond->waiter_count || !win32_cond->is_broadcast;
230     pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
231
232     if (last_waiter)
233         SetEvent(win32_cond->waiters_done);
234
235     // lock the external mutex
236     return pthread_mutex_lock(mutex);
237 }
238
239 static void pthread_cond_signal(pthread_cond_t *cond)
240 {
241     win32_cond_t *win32_cond = cond->ptr;
242     int have_waiter;
243     if (cond_signal) {
244         cond_signal(cond);
245         return;
246     }
247
248     pthread_mutex_lock(&win32_cond->mtx_broadcast);
249
250     /* non-native condition variables */
251     pthread_mutex_lock(&win32_cond->mtx_waiter_count);
252     have_waiter = win32_cond->waiter_count;
253     pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
254
255     if (have_waiter) {
256         ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
257         WaitForSingleObject(win32_cond->waiters_done, INFINITE);
258         ResetEvent(win32_cond->waiters_done);
259     }
260
261     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
262 }
263
264 static void w32thread_init(void)
265 {
266 #if _WIN32_WINNT < 0x0600
267     HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
268     /* if one is available, then they should all be available */
269     cond_init      =
270         (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
271     cond_broadcast =
272         (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
273     cond_signal    =
274         (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
275     cond_wait      =
276         (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
277 #endif
278
279 }
280
281 #endif /* LIBAV_COMPAT_W32PTHREADS_H */