src/win32/mta_holder.h

   1 /*****************************************************************************
   2  * mta_holder.c: Hold a MTA from another thread
   3  *****************************************************************************
   4  * Copyright (C) 2002-2017 the VideoLAN and AUTHORS
   5  *
   6  * Author: Hugo Beauzée-Luyssen <hugo@beauzee.fr>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  21  *****************************************************************************/
  22
  23 #ifndef MTA_HOLDER_H
  24 # define MTA_HOLDER_H
  25
  26 #include <vlc_common.h>
  27
  28 #include <assert.h>
  29 #include <windows.h>
  30 #include <objbase.h>
  31
  32 typedef struct vlc_mta_holder
  33 {
  34     vlc_thread_t thread;
  35     int          i_refcount;
  36     vlc_sem_t    ready_sem;
  37     vlc_sem_t    release_sem;
  38 } vlc_mta_holder;
  39
  40 static inline void* MtaMainLoop( void* opaque )
  41 {
  42     vlc_mta_holder* p_mta = (vlc_mta_holder*)opaque;
  43     CoInitializeEx( NULL, COINIT_MULTITHREADED );
  44
  45     vlc_sem_post( &p_mta->ready_sem );
  46
  47     vlc_sem_wait( &p_mta->release_sem );
  48
  49     CoUninitialize();
  50     return NULL;
  51 }
  52
  53 /**
  54  * Ensure an MTA context will be available until vlc_mta_release gets called.
  55  *
  56  * In the background, this will create a thread that does nothing but to keep the MTA
  57  * refcount greater than 0.
  58  *
  59  * This is usefull in order not to commit a thread to a specific concurrency model.
  60  * This function is win32 specific.
  61  */
  62 static inline bool vlc_mta_acquire( vlc_object_t *p_parent )
  63 {
  64     vlc_global_lock( VLC_MTA_MUTEX );
  65     vlc_mta_holder* p_mta = (vlc_mta_holder*)var_CreateGetAddress( p_parent->obj.libvlc, "mta-holder" );
  66     if ( p_mta == NULL )
  67     {
  68         p_mta = (vlc_mta_holder*)malloc( sizeof( *p_mta ) );
  69         if ( unlikely( p_mta == NULL ) )
  70         {
  71             vlc_global_unlock( VLC_MTA_MUTEX );
  72             return false;
  73         }
  74         vlc_sem_init( &p_mta->ready_sem, 0 );
  75         vlc_sem_init( &p_mta->release_sem, 0 );
  76         p_mta->i_refcount = 1;
  77         if ( vlc_clone( &p_mta->thread, MtaMainLoop, p_mta, VLC_THREAD_PRIORITY_LOW ) )
  78         {
  79             vlc_sem_destroy( &p_mta->release_sem );
  80             vlc_sem_destroy( &p_mta->ready_sem );
  81             free( p_mta );
  82             p_mta = NULL;
  83             vlc_global_unlock( VLC_MTA_MUTEX );
  84             return false;
  85         }
  86         var_SetAddress( p_parent->obj.libvlc, "mta-holder", p_mta );
  87         vlc_sem_wait( &p_mta->ready_sem );
  88     }
  89     else
  90         ++p_mta->i_refcount;
  91     vlc_global_unlock( VLC_MTA_MUTEX );
  92     return true;
  93 }
  94
  95 /**
  96  * Releases a reference to the MTA holder.
  97  *
  98  * When its refcount reaches 0, the thread created by
  99  */
 100 static inline void vlc_mta_release( vlc_object_t* p_parent )
 101 {
 102     vlc_global_lock( VLC_MTA_MUTEX );
 103     vlc_mta_holder *p_mta = (vlc_mta_holder*)var_InheritAddress( p_parent->obj.libvlc, "mta-holder" );
 104     assert( p_mta != NULL );
 105     int i_refcount = --p_mta->i_refcount;
 106     if ( i_refcount == 0 )
 107         var_SetAddress( p_parent->obj.libvlc, "mta-holder", NULL );
 108     vlc_global_unlock( VLC_MTA_MUTEX );
 109     if ( i_refcount == 0 )
 110     {
 111         vlc_sem_post( &p_mta->release_sem );
 112
 113         vlc_join( p_mta->thread, NULL );
 114
 115         vlc_sem_destroy( &p_mta->release_sem );
 116         vlc_sem_destroy( &p_mta->ready_sem );
 117         free( p_mta );
 118     }
 119 }
 120
 121 #endif