libavcodec/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 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;
  58 } pthread_cond_t;
  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 }
  99 static inline int pthread_mutex_destroy(pthread_mutex_t *m)
 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 }
 109 static inline int pthread_mutex_unlock(pthread_mutex_t *m)
 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 {
 118     pthread_mutex_t mtx_broadcast;
 119     pthread_mutex_t mtx_waiter_count;
 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
 146     pthread_mutex_init(&win32_cond->mtx_waiter_count, NULL);
 147     pthread_mutex_init(&win32_cond->mtx_broadcast, NULL);
 148 }
 149
 150 static void pthread_cond_destroy(pthread_cond_t *cond)
 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);
 160     pthread_mutex_destroy(&win32_cond->mtx_waiter_count);
 161     pthread_mutex_destroy(&win32_cond->mtx_broadcast);
 162     av_freep(&win32_cond);
 163     cond->ptr = NULL;
 164 }
 165
 166 static void pthread_cond_broadcast(pthread_cond_t *cond)
 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);
 188         pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
 189         WaitForSingleObject(win32_cond->waiters_done, INFINITE);
 190         ResetEvent(win32_cond->waiters_done);
 191         win32_cond->is_broadcast = 0;
 192     } else
 193         pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
 194     pthread_mutex_unlock(&win32_cond->mtx_broadcast);
 195 }
 196
 197 static void pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 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++;
 210     pthread_mutex_unlock(&win32_cond->mtx_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;
 220     pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
 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
 229 static void pthread_cond_signal(pthread_cond_t *cond)
 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;
 243     pthread_mutex_unlock(&win32_cond->mtx_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 */