text: /*
  	alsa: sound output with Advanced Linux Sound Architecture 1.x API
  
  	copyright 2006-2020 by the mpg123 project - free software under the terms of the LGPL 2.1
  	see COPYING and AUTHORS files in distribution or http://mpg123.org
  
  	initially written by Clemens Ladisch <clemens@ladisch.de>
  */
  
  /* ALSA headers define struct timeval if no POSIX macro is set,
     nicely in conflict with definitions in system headers. They had
     a discussion about that a long time ago:
       http://mailman.alsa-project.org/pipermail/alsa-devel/2007-June/001684.html
     ... seems like the conclusion was not carried through.
   */
  #define _POSIX_SOURCE
  /* Things are still missing if _DEFAULT_SOURCE is not defined (for recent
     glibc, I presume. */
  #define _DEFAULT_SOURCE
  #include "out123_int.h"
  #include <errno.h>
  
  /* make ALSA 0.9.x compatible to the 1.0.x API */
  #define ALSA_PCM_NEW_HW_PARAMS_API
  #define ALSA_PCM_NEW_SW_PARAMS_API
  
  #include <alloca.h> /* GCC complains about missing declaration of alloca. */
  #include <alsa/asoundlib.h>
  
  #include "debug.h"
  
  /* Total buffer size in seconds, 0.2 is more true to what ALSA maximally uses
     here (8192 samples). The earlier default of 0.5 was never true. */
  #define BUFFER_LENGTH (ao->device_buffer > 0. ? ao->device_buffer : 0.2)
  
  static const struct {
  	snd_pcm_format_t alsa;
  	int mpg123;
  } format_map[] = {
  	{ SND_PCM_FORMAT_S16,    MPG123_ENC_SIGNED_16   },
  	{ SND_PCM_FORMAT_U16,    MPG123_ENC_UNSIGNED_16 },
  	{ SND_PCM_FORMAT_U8,     MPG123_ENC_UNSIGNED_8  },
  	{ SND_PCM_FORMAT_S8,     MPG123_ENC_SIGNED_8    },
  	{ SND_PCM_FORMAT_A_LAW,  MPG123_ENC_ALAW_8      },
  	{ SND_PCM_FORMAT_MU_LAW, MPG123_ENC_ULAW_8      },
  	{ SND_PCM_FORMAT_S32,    MPG123_ENC_SIGNED_32   },
  	{ SND_PCM_FORMAT_U32,    MPG123_ENC_UNSIGNED_32 },
  #ifdef WORDS_BIGENDIAN
  	{ SND_PCM_FORMAT_S24_3BE, MPG123_ENC_SIGNED_24   },
  	{ SND_PCM_FORMAT_U24_3BE, MPG123_ENC_UNSIGNED_24 },
  #else
  	{ SND_PCM_FORMAT_S24_3LE, MPG123_ENC_SIGNED_24   },
  	{ SND_PCM_FORMAT_U24_3LE, MPG123_ENC_UNSIGNED_24 },
  #endif
  	{ SND_PCM_FORMAT_FLOAT,  MPG123_ENC_FLOAT_32    },
  	{ SND_PCM_FORMAT_FLOAT64, MPG123_ENC_FLOAT_64   }
  };
  #define NUM_FORMATS (sizeof format_map / sizeof format_map[0])
  
  
  static int rates_match(long int desired, unsigned int actual)
  {
  	return actual * 100 > desired * (100 - AUDIO_RATE_TOLERANCE) &&
  	       actual * 100 < desired * (100 + AUDIO_RATE_TOLERANCE);
  }
  
  static int initialize_device(out123_handle *ao)
  {
  	snd_pcm_hw_params_t *hw=NULL;
  	snd_pcm_sw_params_t *sw=NULL;
  	snd_pcm_uframes_t buffer_size;
  	snd_pcm_uframes_t period_size;
  	snd_pcm_format_t format;
  	snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
  	unsigned int rate;
  	int i;
  
  	snd_pcm_hw_params_alloca(&hw); /* Ignore GCC warning here... alsa-lib>=1.0.16 doesn't trigger that anymore, too. */
  	if (snd_pcm_hw_params_any(pcm, hw) < 0) {
  		if(!AOQUIET) error("initialize_device(): no configuration available");
  		return -1;
  	}
  	if (snd_pcm_hw_params_set_access(pcm, hw, SND_PCM_ACCESS_RW_INTERLEAVED) < 0) {
  		if(!AOQUIET) error("initialize_device(): device does not support interleaved access");
  		return -1;
  	}
  	format = SND_PCM_FORMAT_UNKNOWN;
  	for (i = 0; i < NUM_FORMATS; ++i) {
  		if (ao->format == format_map[i].mpg123) {
  			format = format_map[i].alsa;
  			break;
  		}
  	}
  	if (format == SND_PCM_FORMAT_UNKNOWN) {
  		if(!AOQUIET) error1("initialize_device(): invalid sample format %d", ao->format);
  		errno = EINVAL;
  		return -1;
  	}
  	if (snd_pcm_hw_params_set_format(pcm, hw, format) < 0) {
  		if(!AOQUIET) error1("initialize_device(): cannot set format %s", snd_pcm_format_name(format));
  		return -1;
  	}
  	if (snd_pcm_hw_params_set_channels(pcm, hw, ao->channels) < 0) {
  		if(!AOQUIET) error1("initialize_device(): cannot set %d channels", ao->channels);
  		return -1;
  	}
  	rate = ao->rate;
  	if (snd_pcm_hw_params_set_rate_near(pcm, hw, &rate, NULL) < 0) {
  		if(!AOQUIET) error1("initialize_device(): cannot set rate %u", rate);
  		return -1;
  	}
  	if (!rates_match(ao->rate, rate)) {
  		if(!AOQUIET) error2("initialize_device(): rate %ld not available, using %u", ao->rate, rate);
  		/* return -1; */
  	}
  	buffer_size = rate * BUFFER_LENGTH;
  	if (snd_pcm_hw_params_set_buffer_size_near(pcm, hw, &buffer_size) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot set buffer size");
  		return -1;
  	}
  	debug1("buffer_size=%lu", (unsigned long)buffer_size);
  	period_size = buffer_size / 3; /* 3 periods is so much more common. */
  	if (snd_pcm_hw_params_set_period_size_near(pcm, hw, &period_size, NULL) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot set period size");
  		return -1;
  	}
  	debug1("period_size=%lu", (unsigned long)period_size);
  	if (snd_pcm_hw_params(pcm, hw) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot set hw params");
  		return -1;
  	}
  
  	snd_pcm_sw_params_alloca(&sw);
  	if (snd_pcm_sw_params_current(pcm, sw) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot get sw params");
  		return -1;
  	}
  	/* Start playing once we got at least full period ... this is not default? */
  	if (snd_pcm_sw_params_set_start_threshold(pcm, sw, buffer_size/2) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot set start threshold");
  		return -1;
  	}
  	/* wake up on every interrupt */
  	if (snd_pcm_sw_params_set_avail_min(pcm, sw, 1) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot set min available");
  		return -1;
  	}
  #if SND_LIB_VERSION < ((1<<16)|16)
  	/* Always write as many frames as possible (deprecated since alsa-lib 1.0.16) */
  	if (snd_pcm_sw_params_set_xfer_align(pcm, sw, 1) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot set transfer alignment");
  		return -1;
  	}
  #endif
  	if (snd_pcm_sw_params(pcm, sw) < 0) {
  		if(!AOQUIET) error("initialize_device(): cannot set sw params");
  		return -1;
  	}
  	return 0;
  }
  
  #ifndef DEBUG
  static void error_ignorer(const char *file, int line, const char *function, int err, const char *fmt,...)
  {
  	/* I can make ALSA silent. */
  }
  #endif
  
  static int open_alsa(out123_handle *ao)
  {
  	const char *pcm_name;
  	snd_pcm_t *pcm=NULL;
  	debug1("open_alsa with %p", ao->userptr);
  
  #ifndef DEBUG
  	if(AOQUIET) snd_lib_error_set_handler(error_ignorer);
  #endif
  
  	pcm_name = ao->device ? ao->device : "default";
  	if (snd_pcm_open(&pcm, pcm_name, SND_PCM_STREAM_PLAYBACK, 0) < 0) {
  		if(!AOQUIET) error1("cannot open device %s", pcm_name);
  		return -1;
  	}
  	ao->userptr = pcm;
  	if (ao->format != -1) {
  		/* we're going to play: initalize sample format */
  		return initialize_device(ao);
  	} else {
  		/* query mode; sample format will be set for each query */
  		return 0;
  	}
  }
  
  
  static int get_formats_alsa(out123_handle *ao)
  {
  	snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
  	snd_pcm_hw_params_t *hw;
  	unsigned int rate;
  	int supported_formats, i;
  
  	snd_pcm_hw_params_alloca(&hw);
  	if (snd_pcm_hw_params_any(pcm, hw) < 0) {
  		if(!AOQUIET) error("get_formats_alsa(): no configuration available");
  		return -1;
  	}
  	if (snd_pcm_hw_params_set_access(pcm, hw, SND_PCM_ACCESS_RW_INTERLEAVED) < 0)
  		return -1;
  	if (snd_pcm_hw_params_set_channels(pcm, hw, ao->channels) < 0)
  		return 0;
  	rate = ao->rate;
  	if (snd_pcm_hw_params_set_rate_near(pcm, hw, &rate, NULL) < 0)
  		return -1;
  	if (!rates_match(ao->rate, rate))
  		return 0;
  	supported_formats = 0;
  	for (i = 0; i < NUM_FORMATS; ++i) {
  		if (snd_pcm_hw_params_test_format(pcm, hw, format_map[i].alsa) == 0)
  			supported_formats |= format_map[i].mpg123;
  	}
  	return supported_formats;
  }
  
  static int write_alsa(out123_handle *ao, unsigned char *buf, int bytes)
  {
  	snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
  	snd_pcm_uframes_t frames;
  	snd_pcm_sframes_t written;
  
  	frames = snd_pcm_bytes_to_frames(pcm, bytes);
  	while
  	( /* Try to write, recover if error, try again if recovery successful. */
  		(written = snd_pcm_writei(pcm, buf, frames)) < 0
  		&& snd_pcm_recover(pcm, (int)written, 0) == 0
  	)
  	{
  		debug2("recovered from alsa issue %i while trying to write %lu frames", (int)written, (unsigned long)frames);
  	}
  	if(written < 0)
  	{
  		if(!AOQUIET)
  			error1("Fatal problem with alsa output, error %i.", (int)written);
  		return -1;
  	}
  	else return snd_pcm_frames_to_bytes(pcm, written);
  }
  
  static void flush_alsa(out123_handle *ao)
  {
  	snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
  
  	/* is this the optimal solution? - we should figure out what we really whant from this function */
  
  debug("alsa drop");
  	snd_pcm_drop(pcm);
  debug("alsa prepare");
  	snd_pcm_prepare(pcm);
  debug("alsa flush done");
  }
  
  static void drain_alsa(out123_handle *ao)
  {
  	snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
  	debug1("drain_alsa with %p", ao->userptr);
  	snd_pcm_drain(pcm);
  }
  
  static int close_alsa(out123_handle *ao)
  {
  	snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr;
  	debug1("close_alsa with %p", ao->userptr);
  	if(pcm != NULL) /* be really generous for being called without any device opening */
  	{
  		ao->userptr = NULL; /* Should alsa do this or the module wrapper? */
  		return snd_pcm_close(pcm);
  	}
  	else return 0;
  }
  
  static int enumerate_alsa( out123_handle *ao, int (*store_device)(void *devlist
  ,	const char *name, const char *description), void *devlist )
  {
  	void ** hints;
  	int ret = snd_device_name_hint(-1, "pcm", &hints);
  	if(ret)
  	{
  		if(!AOQUIET)
  			merror("ALSA device listing failed with code %d.", ret);
  		return -1;
  	}
  	void ** hint = hints;
  	while(!ret && *hint)
  	{
  		char *io = snd_device_name_get_hint(*hint, "IOID");
  		if((io == NULL || !strcmp("Output", io)))
  		{
  			char *name = snd_device_name_get_hint(*hint, "NAME");
  			char *desc = snd_device_name_get_hint(*hint, "DESC");
  			ret = store_device(devlist, name, desc);
  			free(name);
  			free(desc);
  		}
  		free(io);
  		++hint;
  	}
  	snd_device_name_free_hint(hints);
  	return 0;
  }
  
  static int init_alsa(out123_handle* ao)
  {
  	if (ao==NULL) return -1;
  
  	/* Set callbacks */
  	ao->open = open_alsa;
  	ao->flush = flush_alsa;
  	ao->drain = drain_alsa;
  	ao->write = write_alsa;
  	ao->get_formats = get_formats_alsa;
  	ao->close = close_alsa;
  	ao->enumerate = enumerate_alsa;
  
  	/* Success */
  	return 0;
  }
  /* 
  	Module information data structure
  */
  mpg123_module_t mpg123_output_module_info = {
  	/* api_version */	MPG123_MODULE_API_VERSION,
  	/* name */			"alsa",						
  	/* description */	"Output audio using Advanced Linux Sound Architecture (ALSA).",
  	/* revision */		"$Rev:$",						
  	/* handle */		NULL,
  	
  	/* init_output */	init_alsa,						
  };
  
  