Appendix: wave.c example

This is a sample application that plays back audio data:

#include <errno.h>
#include <fcntl.h>
#include <gulliver.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/termio.h>
#include <sys/types.h>
#include <unistd.h>

#include <sys/asoundlib.h>


const char *kRiffId = "RIFF";
const char *kWaveId = "WAVE";

typedef struct
{
    char    tag[4];
    long    length;
}
RiffTag;

typedef struct
{
    char    Riff[4];
    long    Size;
    char    Wave[4];
}
RiffHdr;


typedef struct
{
    short   FormatTag;
    short   Channels;
    long    SamplesPerSec;
    long    AvgBytesPerSec;
    short   BlockAlign;
    short   BitsPerSample;
}
WaveHdr;


int
err (char *msg)
{
    perror (msg);
    return -1;
}


int
FindTag (FILE * fp, const char *tag)
{
    int     retVal;
    RiffTag tagBfr =
    {"", 0};

    retVal = 0;

    // Keep reading until we find the tag or hit the EOF.
    while (fread ((unsigned char *) &tagBfr, sizeof (tagBfr), 1, fp))
    {

        // If this is our tag, set the length and break.    
        if (strncmp (tag, tagBfr.tag, sizeof tagBfr.tag) == 0)
        {
            retVal = ENDIAN_LE32(tagBfr.length);
            break;
        }

        // Skip ahead the specified number of bytes in the stream           
        fseek (fp, tagBfr.length, SEEK_CUR);
    }

    // Return the result of our operation
    return (retVal);
}


int
CheckHdr (FILE * fp)
{
    RiffHdr riffHdr =
    {"", 0};

    // Read the header and, if successful, play the file
    // file or WAVE file.
    if (fread ((unsigned char *) &riffHdr, sizeof (RiffHdr), 1, fp) == 0)
        return 0;

    if (strncmp (riffHdr.Riff, kRiffId, strlen (kRiffId)) ||
        strncmp (riffHdr.Wave, kWaveId, strlen (kWaveId)))
        return -1;

    return 0;
}


int
dev_raw (int fd)
{
    struct termios termios_p;

    if (tcgetattr (fd, &termios_p))
        return (-1);

    termios_p.c_cc[VMIN] = 1;
    termios_p.c_cc[VTIME] = 0;
    termios_p.c_lflag &= ~(ECHO | ICANON | ISIG |
        ECHOE | ECHOK | ECHONL);
    termios_p.c_oflag &= ~(OPOST);
    return (tcsetattr (fd, TCSANOW, &termios_p));
}

int
dev_unraw (int fd)
{
    struct termios termios_p;

    if (tcgetattr (fd, &termios_p))
        return (-1);

    termios_p.c_lflag |= (ECHO | ICANON | ISIG |
        ECHOE | ECHOK | ECHONL);
    termios_p.c_oflag |= (OPOST);
    return (tcsetattr (fd, TCSAFLUSH, &termios_p));
}


//*****************************************************************************
/* *INDENT-OFF* */
#ifdef __USAGE
%C[Options] *

Options:
    -a[card#:]<dev#>  the card & device number to play out on
#endif
/* *INDENT-ON* */
//*****************************************************************************


int
main (int argc, char **argv)
{
    int     card = -1;
    int     dev = 0;
    snd_pcm_t *pcm_handle;
    FILE   *file1;
    WaveHdr wavHdr1;
    int     mSamples;
    int     mSampleRate;
    int     mSampleChannels;
    int     mSampleBits;
    char   *mSampleBfr1;

    int     rtn;
    snd_pcm_channel_info_t pi;
    snd_mixer_t *mixer_handle;
    snd_mixer_group_t group;
    snd_pcm_channel_params_t pp;
    snd_pcm_channel_setup_t setup;
    int     bsize, n, N = 0, c;
    fd_set  rfds, wfds;


    while ((c = getopt (argc, argv, "a:")) != EOF)
    {
        switch (c)
        {
        case 'a':
            if (strchr (optarg, ':'))
            {
                card = atoi (optarg);
                dev = atoi (strchr (optarg, ':') + 1);
            }
            else
                dev = atoi (optarg);
            printf ("Using card %d device %d \n", card, dev);
            break;
        default:
            return 1;
        }
    }

    setvbuf (stdin, NULL, _IONBF, 0);
    if (card == -1)
    {
        if ((rtn = snd_pcm_open_preferred (&pcm_handle, &card, &dev, SND_PCM_OPEN_PLAYBACK)) < 0)
            return err ("device open");
    }
    else
    {
        if ((rtn = snd_pcm_open (&pcm_handle, card, dev, SND_PCM_OPEN_PLAYBACK)) < 0)
            return err ("device open");
    }

    if (argc < 2)
        return err ("no file specified");

    if ((file1 = fopen (argv[optind], "r")) == 0)
        return err ("file open #1");

    if (CheckHdr (file1) == -1)
        return err ("CheckHdr #1");

    mSamples = FindTag (file1, "fmt ");
    fread (&wavHdr1, sizeof (wavHdr1), 1, file1);
    fseek (file1, (mSamples - sizeof (WaveHdr)), SEEK_CUR);

    mSampleRate = ENDIAN_LE32(wavHdr1.SamplesPerSec);
    mSampleChannels = ENDIAN_LE16(wavHdr1.Channels);
    mSampleBits = ENDIAN_LE16(wavHdr1.BitsPerSample);

    printf ("SampleRate = %d, Channels = %d, SampleBits = %d\n", mSampleRate, mSampleChannels, mSampleBits);

    /* disabling mmap is not actually required in this example but it is included to 
     * demonstrate how it is used when it is required.
     */
    if ((rtn = snd_pcm_plugin_set_disable (pcm_handle, PLUGIN_DISABLE_MMAP)) < 0)
    {
        fprintf (stderr, "snd_pcm_plugin_set_disable failed: %s\n", snd_strerror (rtn));
        return -1;
    }

    memset (&pi, 0, sizeof (pi));
    pi.channel = SND_PCM_CHANNEL_PLAYBACK;
    if ((rtn = snd_pcm_plugin_info (pcm_handle, &pi)) < 0)
    {
        fprintf (stderr, "snd_pcm_plugin_info failed: %s\n", snd_strerror (rtn));
        return -1;
    }

    memset (&pp, 0, sizeof (pp));

    pp.mode = SND_PCM_MODE_BLOCK;
    pp.channel = SND_PCM_CHANNEL_PLAYBACK;
    pp.start_mode = SND_PCM_START_FULL;
    pp.stop_mode = SND_PCM_STOP_STOP;

    pp.buf.block.frag_size = pi.max_fragment_size;
    pp.buf.block.frags_max = 1;
    pp.buf.block.frags_min = 1;

    pp.format.interleave = 1;
    pp.format.rate = mSampleRate;
    pp.format.voices = mSampleChannels;

    if (mSampleBits == 8)
        pp.format.format = SND_PCM_SFMT_U8;
    else
        pp.format.format = SND_PCM_SFMT_S16_LE;

    if ((rtn = snd_pcm_plugin_params (pcm_handle, &pp)) < 0)
    {
        fprintf (stderr, "snd_pcm_plugin_params failed: %s\n", snd_strerror (rtn));
        return -1;
    }

    if ((rtn = snd_pcm_plugin_prepare (pcm_handle, SND_PCM_CHANNEL_PLAYBACK)) < 0)
        fprintf (stderr, "snd_pcm_plugin_prepare failed: %s\n", snd_strerror (rtn));


    memset (&setup, 0, sizeof (setup));
    memset (&group, 0, sizeof (group));
    setup.channel = SND_PCM_CHANNEL_PLAYBACK;
    setup.mixer_gid = &group.gid;
    if ((rtn = snd_pcm_plugin_setup (pcm_handle, &setup)) < 0)
    {
        fprintf (stderr, "snd_pcm_plugin_setup failed: %s\n", snd_strerror (rtn));
        return -1;
    }
    printf ("Format %s \n", snd_pcm_get_format_name (setup.format.format));
    printf ("Frag Size %d \n", setup.buf.block.frag_size);
    printf ("Rate %d \n", setup.format.rate);
    bsize = setup.buf.block.frag_size;

    if (group.gid.name[0] == 0)
    {
        printf ("Mixer Pcm Group [%s] Not Set \n", group.gid.name);
        exit (-1);
    }
    printf ("Mixer Pcm Group [%s]\n", group.gid.name);
    if ((rtn = snd_mixer_open (&mixer_handle, card, setup.mixer_device)) < 0)
    {
        fprintf (stderr, "snd_mixer_open failed: %s\n", snd_strerror (rtn));
        return -1;
    }

    mSamples = FindTag (file1, "data");

    mSampleBfr1 = malloc (bsize);
    FD_ZERO (&rfds);
    FD_ZERO (&wfds);
    n = 1;
    while (N < mSamples && n > 0)
    {
        FD_SET (STDIN_FILENO, &rfds);
        FD_SET (snd_mixer_file_descriptor (mixer_handle), &rfds);
        FD_SET (snd_pcm_file_descriptor (pcm_handle, SND_PCM_CHANNEL_PLAYBACK), &wfds);

        rtn = max (snd_mixer_file_descriptor (mixer_handle),
            snd_pcm_file_descriptor (pcm_handle, SND_PCM_CHANNEL_PLAYBACK));

        if (select (rtn + 1, &rfds, &wfds, NULL, NULL) == -1)
            return err ("select");


        if (FD_ISSET (STDIN_FILENO, &rfds))
        {
            if ((rtn = snd_mixer_group_read (mixer_handle, &group)) < 0)
                fprintf (stderr, "snd_mixer_group_read failed: %s\n", snd_strerror (rtn));

            dev_raw (fileno (stdin));
            c = getc (stdin);
            dev_unraw (fileno (stdin));
            if (c != EOF)
            {
                switch (c)
                {
                case 'q':
                    group.volume.names.front_left += 10;
                    break;
                case 'a':
                    group.volume.names.front_left -= 10;
                    break;
                case 'w':
                    group.volume.names.front_left += 10;
                    group.volume.names.front_right += 10;
                    break;
                case 's':
                    group.volume.names.front_left -= 10;
                    group.volume.names.front_right -= 10;
                    break;
                case 'e':
                    group.volume.names.front_right += 10;
                    break;
                case 'd':
                    group.volume.names.front_right -= 10;
                    break;
                }
                if (group.volume.names.front_left > group.max)
                    group.volume.names.front_left = group.max;
                if (group.volume.names.front_left < group.min)
                    group.volume.names.front_left = group.min;
                if (group.volume.names.front_right > group.max)
                    group.volume.names.front_right = group.max;
                if (group.volume.names.front_right < group.min)
                    group.volume.names.front_right = group.min;
                if ((rtn = snd_mixer_group_write (mixer_handle, &group)) < 0)
                    fprintf (stderr, "snd_mixer_group_write failed: %s\n", snd_strerror (rtn));
            }
            else
                exit (0);

            printf ("Volume Now at %d:%d \n",
                100 * (group.volume.names.front_left - group.min) / (group.max - group.min),
                100 * (group.volume.names.front_right - group.min) / (group.max - group.min));

        }

        if (FD_ISSET (snd_mixer_file_descriptor (mixer_handle), &rfds))
        {
            snd_mixer_callbacks_t callbacks =
            {0, 0, 0, 0};

            snd_mixer_read (mixer_handle, &callbacks);
        }

        if (FD_ISSET (snd_pcm_file_descriptor (pcm_handle, SND_PCM_CHANNEL_PLAYBACK), &wfds))
        {
            snd_pcm_channel_status_t status;
            int     written = 0;

            if ((n = fread (mSampleBfr1, 1, min (mSamples - N, bsize), file1)) <= 0)
                continue;
            written = snd_pcm_plugin_write (pcm_handle, mSampleBfr1, n);
            if (written < n)
            {
                memset (&status, 0, sizeof (status));
                status.channel = SND_PCM_CHANNEL_PLAYBACK;
                if (snd_pcm_plugin_status (pcm_handle, &status) < 0)
                {
                    fprintf (stderr, "underrun: playback channel status error\n");
                    exit (1);
                }

                if (status.status == SND_PCM_STATUS_READY ||
                    status.status == SND_PCM_STATUS_UNDERRUN)
                {
                    if (snd_pcm_plugin_prepare (pcm_handle, SND_PCM_CHANNEL_PLAYBACK) < 0)
                    {
                        fprintf (stderr, "underrun: playback channel prepare error\n");
                        exit (1);
                    }
                }
                if (written < 0)
                    written = 0;
                written += snd_pcm_plugin_write (pcm_handle, mSampleBfr1 + written, n - written);
            }
            N += written;
        }
    }

    n = snd_pcm_plugin_flush (pcm_handle, SND_PCM_CHANNEL_PLAYBACK);

    rtn = snd_mixer_close (mixer_handle);
    rtn = snd_pcm_close (pcm_handle);
    fclose (file1);
    return (0);
}