allegro_s.cpp

Go to the documentation of this file.

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD 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 General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifdef WITH_ALLEGRO
 
#include "../stdafx.h"
 
#include "../mixer.h"
#include "../debug.h"
#include "allegro_s.h"
#include <allegro.h>
 
#include "../safeguards.h"
 
static FSoundDriver_Allegro iFSoundDriver_Allegro;
static AUDIOSTREAM *_stream = nullptr;
static int _buffer_size;
 
void SoundDriver_Allegro::MainLoop()
{
  /* We haven't opened a stream yet */
  if (_stream == nullptr) return;
 
  void *data = get_audio_stream_buffer(_stream);
  /* We don't have to fill the stream yet */
  if (data == nullptr) return;
 
  /* Mix the samples */
  MxMixSamples(data, _buffer_size);
 
  /* Allegro sound is always unsigned, so we need to correct that */
  uint16_t *snd = (uint16_t*)data;
  for (int i = 0; i < _buffer_size * 2; i++) snd[i] ^= 0x8000;
 
  /* Tell we've filled the stream */
  free_audio_stream_buffer(_stream);
}
 
extern int _allegro_instance_count;
 
std::optional<std::string_view> SoundDriver_Allegro::Start(const StringList &parm)
{
  if (_allegro_instance_count == 0 && install_allegro(SYSTEM_AUTODETECT, &errno, nullptr)) {
    Debug(driver, 0, "allegro: install_allegro failed '{}'", allegro_error);
    return "Failed to set up Allegro";
  }
  _allegro_instance_count++;
 
  /* Initialise the sound */
  if (install_sound(DIGI_AUTODETECT, MIDI_AUTODETECT, nullptr) != 0) {
    Debug(driver, 0, "allegro: install_sound failed '{}'", allegro_error);
    return "Failed to set up Allegro sound";
  }
 
  /* Okay, there's no soundcard */
  if (digi_card == DIGI_NONE) {
    Debug(driver, 0, "allegro: no sound card found");
    return "No sound card found";
  }
 
  int hz = GetDriverParamInt(parm, "hz", 44100);
  _buffer_size = GetDriverParamInt(parm, "samples", 1024) * hz / 11025;
  _stream = play_audio_stream(_buffer_size, 16, true, hz, 255, 128);
  MxInitialize(hz);
  return std::nullopt;
}
 
void SoundDriver_Allegro::Stop()
{
  if (_stream != nullptr) {
    stop_audio_stream(_stream);
    _stream = nullptr;
  }
  remove_sound();
 
  if (--_allegro_instance_count == 0) allegro_exit();
}
 
#endif /* WITH_ALLEGRO */