alsa-lib/src/pcm/pcm_loopback.c

/*
 *  PCM LoopBack Interface - main file
 *  Copyright (c) 1998 by Jaroslav Kysela <perex@jcu.cz>
 *
 *
 *   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 program 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include "asoundlib.h"

#define SND_FILE_PCM_LB		"/proc/asound/%i/pcm%i%s"
#define SND_PCM_LB_VERSION_MAX	SND_PROTOCOL_VERSION( 1, 0, 0 )
 
typedef struct {
  int card;
  int device;
  int fd;
} snd_pcm_loopback_t;
 
int snd_pcm_loopback_open( void **handle, int card, int device, int mode )
{
  int fd, ver;
  char filename[32];
  snd_pcm_loopback_t *lb;

  *handle = NULL;
  if ( card < 0 || card >= SND_CARDS ) return -EINVAL;
  sprintf( filename, SND_FILE_PCM_LB, card, device,
  	   mode == SND_PCM_LB_OPEN_RECORD ? "r" : "p" );
  if ( (fd = open( filename, mode )) < 0 ) return -errno;
  if ( ioctl( fd, SND_PCM_IOCTL_PVERSION, &ver ) < 0 ) {
    close( fd );
    return -errno;
  }
  if ( SND_PROTOCOL_UNCOMPATIBLE( ver, SND_PCM_LB_VERSION_MAX ) ) {
    close( fd );
    return -SND_ERROR_UNCOMPATIBLE_VERSION;
  }
  lb = (snd_pcm_loopback_t *)calloc( 1, sizeof( snd_pcm_loopback_t ) );
  if ( lb == NULL ) {
    close( fd );
    return -ENOMEM;
  }
  lb -> card = card;
  lb -> device = device;
  lb -> fd = fd;
  *handle = lb;
  return 0;
}

int snd_pcm_loopback_close( void *handle )
{
  snd_pcm_loopback_t *lb;
  int res;
  
  lb = (snd_pcm_loopback_t *)handle;
  if ( !lb ) return -EINVAL;
  res = close( lb -> fd ) < 0 ? -errno : 0;
  free( lb );
  return res;
}

int snd_pcm_loopback_file_descriptor( void *handle )
{
  snd_pcm_loopback_t *lb;
  
  lb = (snd_pcm_loopback_t *)handle;
  if ( !lb ) return -EINVAL;
  return lb -> fd;
}

int snd_pcm_loopback_block_mode( void *handle, int enable )
{
  snd_pcm_loopback_t *lb;
  long flags;
  
  lb = (snd_pcm_loopback_t *)handle;
  if ( !lb ) return -EINVAL;
  if ( fcntl( lb -> fd, F_GETFL, &flags ) < 0 )
    return -errno;
  if ( enable )
    flags |= O_NONBLOCK;
   else
    flags &= ~O_NONBLOCK;
  if ( fcntl( lb -> fd, F_SETFL, &flags ) < 0 )
    return -errno;
  return 0;
}

int snd_pcm_loopback_stream_mode( void *handle, int mode )
{
  snd_pcm_loopback_t *lb;
  long lmode = mode;
  
  lb = (snd_pcm_loopback_t *)handle;
  if ( !lb ) return -EINVAL;
  if ( ioctl( lb -> fd, SND_PCM_LB_IOCTL_STREAM_MODE, &lmode ) < 0 )
    return -errno;
  return 0;
}

int snd_pcm_loopback_format( void *handle, snd_pcm_format_t *format )
{
  snd_pcm_loopback_t *lb;
  
  lb = (snd_pcm_loopback_t *)handle;
  if ( !lb ) return -EINVAL;
  if ( ioctl( lb -> fd, SND_PCM_LB_IOCTL_FORMAT, format ) < 0 )
    return -errno;
  return 0;
}

ssize_t snd_pcm_loopback_read( void *handle, void *buffer, size_t size )
{
  snd_pcm_loopback_t *lb;
  ssize_t result;
  
  lb = (snd_pcm_loopback_t *)handle;
  if ( !lb ) return -EINVAL;
  result = read( lb -> fd, buffer, size );
  if ( result < 0 ) return -errno;
  return result;
}