text: /**
   * OpenAL cross platform audio library
   * Copyright (C) 2010 by Chris Robinson
   * This library is free software; you can redistribute it and/or
   *  modify it under the terms of the GNU Library General Public
   *  License as published by the Free Software Foundation; either
   *  version 2 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   *  Library General Public License for more details.
   *
   * You should have received a copy of the GNU Library General Public
   *  License along with this library; if not, write to the
   *  Free Software Foundation, Inc.,
   *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
   * Or go to http://www.gnu.org/copyleft/lgpl.html
   */
  
  #include "config.h"
  
  #include <stdlib.h>
  #ifdef HAVE_WINDOWS_H
  #include <windows.h>
  #endif
  
  #include "alMain.h"
  #include "alu.h"
  #include "threads.h"
  #include "compat.h"
  
  #include "backends/base.h"
  
  
  typedef struct ALCnullBackend {
      DERIVE_FROM_TYPE(ALCbackend);
  
      ATOMIC(int) killNow;
      althrd_t thread;
  } ALCnullBackend;
  
  static int ALCnullBackend_mixerProc(void *ptr);
  
  static void ALCnullBackend_Construct(ALCnullBackend *self, ALCdevice *device);
  static DECLARE_FORWARD(ALCnullBackend, ALCbackend, void, Destruct)
  static ALCenum ALCnullBackend_open(ALCnullBackend *self, const ALCchar *name);
  static ALCboolean ALCnullBackend_reset(ALCnullBackend *self);
  static ALCboolean ALCnullBackend_start(ALCnullBackend *self);
  static void ALCnullBackend_stop(ALCnullBackend *self);
  static DECLARE_FORWARD2(ALCnullBackend, ALCbackend, ALCenum, captureSamples, void*, ALCuint)
  static DECLARE_FORWARD(ALCnullBackend, ALCbackend, ALCuint, availableSamples)
  static DECLARE_FORWARD(ALCnullBackend, ALCbackend, ClockLatency, getClockLatency)
  static DECLARE_FORWARD(ALCnullBackend, ALCbackend, void, lock)
  static DECLARE_FORWARD(ALCnullBackend, ALCbackend, void, unlock)
  DECLARE_DEFAULT_ALLOCATORS(ALCnullBackend)
  
  DEFINE_ALCBACKEND_VTABLE(ALCnullBackend);
  
  
  static const ALCchar nullDevice[] = "No Output";
  
  
  static void ALCnullBackend_Construct(ALCnullBackend *self, ALCdevice *device)
  {
      ALCbackend_Construct(STATIC_CAST(ALCbackend, self), device);
      SET_VTABLE2(ALCnullBackend, ALCbackend, self);
  
      ATOMIC_INIT(&self->killNow, AL_TRUE);
  }
  
  
  static int ALCnullBackend_mixerProc(void *ptr)
  {
      ALCnullBackend *self = (ALCnullBackend*)ptr;
      ALCdevice *device = STATIC_CAST(ALCbackend, self)->mDevice;
      struct timespec now, start;
      ALuint64 avail, done;
      const long restTime = (long)((ALuint64)device->UpdateSize * 1000000000 /
                                   device->Frequency / 2);
  
      SetRTPriority();
      althrd_setname(althrd_current(), MIXER_THREAD_NAME);
  
      done = 0;
      if(altimespec_get(&start, AL_TIME_UTC) != AL_TIME_UTC)
      {
          ERR("Failed to get starting time\n");
          return 1;
      }
      while(!ATOMIC_LOAD(&self->killNow, almemory_order_acquire) &&
            ATOMIC_LOAD(&device->Connected, almemory_order_acquire))
      {
          if(altimespec_get(&now, AL_TIME_UTC) != AL_TIME_UTC)
          {
              ERR("Failed to get current time\n");
              return 1;
          }
  
          avail  = (now.tv_sec - start.tv_sec) * device->Frequency;
          avail += (ALint64)(now.tv_nsec - start.tv_nsec) * device->Frequency / 1000000000;
          if(avail < done)
          {
              /* Oops, time skipped backwards. Reset the number of samples done
               * with one update available since we (likely) just came back from
               * sleeping. */
              done = avail - device->UpdateSize;
          }
  
          if(avail-done < device->UpdateSize)
              al_nssleep(restTime);
          else while(avail-done >= device->UpdateSize)
          {
              ALCnullBackend_lock(self);
              aluMixData(device, NULL, device->UpdateSize);
              ALCnullBackend_unlock(self);
              done += device->UpdateSize;
          }
      }
  
      return 0;
  }
  
  
  static ALCenum ALCnullBackend_open(ALCnullBackend *self, const ALCchar *name)
  {
      ALCdevice *device;
  
      if(!name)
          name = nullDevice;
      else if(strcmp(name, nullDevice) != 0)
          return ALC_INVALID_VALUE;
  
      device = STATIC_CAST(ALCbackend, self)->mDevice;
      alstr_copy_cstr(&device->DeviceName, name);
  
      return ALC_NO_ERROR;
  }
  
  static ALCboolean ALCnullBackend_reset(ALCnullBackend *self)
  {
      SetDefaultWFXChannelOrder(STATIC_CAST(ALCbackend, self)->mDevice);
      return ALC_TRUE;
  }
  
  static ALCboolean ALCnullBackend_start(ALCnullBackend *self)
  {
      ATOMIC_STORE(&self->killNow, AL_FALSE, almemory_order_release);
      if(althrd_create(&self->thread, ALCnullBackend_mixerProc, self) != althrd_success)
          return ALC_FALSE;
      return ALC_TRUE;
  }
  
  static void ALCnullBackend_stop(ALCnullBackend *self)
  {
      int res;
  
      if(ATOMIC_EXCHANGE(&self->killNow, AL_TRUE, almemory_order_acq_rel))
          return;
      althrd_join(self->thread, &res);
  }
  
  
  typedef struct ALCnullBackendFactory {
      DERIVE_FROM_TYPE(ALCbackendFactory);
  } ALCnullBackendFactory;
  #define ALCNULLBACKENDFACTORY_INITIALIZER { { GET_VTABLE2(ALCnullBackendFactory, ALCbackendFactory) } }
  
  ALCbackendFactory *ALCnullBackendFactory_getFactory(void);
  
  static ALCboolean ALCnullBackendFactory_init(ALCnullBackendFactory *self);
  static DECLARE_FORWARD(ALCnullBackendFactory, ALCbackendFactory, void, deinit)
  static ALCboolean ALCnullBackendFactory_querySupport(ALCnullBackendFactory *self, ALCbackend_Type type);
  static void ALCnullBackendFactory_probe(ALCnullBackendFactory *self, enum DevProbe type, al_string *outnames);
  static ALCbackend* ALCnullBackendFactory_createBackend(ALCnullBackendFactory *self, ALCdevice *device, ALCbackend_Type type);
  DEFINE_ALCBACKENDFACTORY_VTABLE(ALCnullBackendFactory);
  
  
  ALCbackendFactory *ALCnullBackendFactory_getFactory(void)
  {
      static ALCnullBackendFactory factory = ALCNULLBACKENDFACTORY_INITIALIZER;
      return STATIC_CAST(ALCbackendFactory, &factory);
  }
  
  
  static ALCboolean ALCnullBackendFactory_init(ALCnullBackendFactory* UNUSED(self))
  {
      return ALC_TRUE;
  }
  
  static ALCboolean ALCnullBackendFactory_querySupport(ALCnullBackendFactory* UNUSED(self), ALCbackend_Type type)
  {
      if(type == ALCbackend_Playback)
          return ALC_TRUE;
      return ALC_FALSE;
  }
  
  static void ALCnullBackendFactory_probe(ALCnullBackendFactory* UNUSED(self), enum DevProbe type, al_string *outnames)
  {
      switch(type)
      {
          case ALL_DEVICE_PROBE:
          case CAPTURE_DEVICE_PROBE:
              alstr_append_range(outnames, nullDevice, nullDevice+sizeof(nullDevice));
              break;
      }
  }
  
  static ALCbackend* ALCnullBackendFactory_createBackend(ALCnullBackendFactory* UNUSED(self), ALCdevice *device, ALCbackend_Type type)
  {
      if(type == ALCbackend_Playback)
      {
          ALCnullBackend *backend;
          NEW_OBJ(backend, ALCnullBackend)(device);
          if(!backend) return NULL;
          return STATIC_CAST(ALCbackend, backend);
      }
  
      return NULL;
  }
  