//linux下基于ALSA驱动的播放wav的源程序
            //欧德浪18年2月2日整理


    #include <stdio.h>
    /* Use the newer ALSA API */
    #define ALSA_PCM_NEW_HW_PARAMS_API

    #include <alsa/asoundlib.h>

    int main() 
    {
        long loops;
        int rc;
        int size;
        snd_pcm_t *handle;
        snd_pcm_hw_params_t *params;
        unsigned int val;
        int dir;
        snd_pcm_uframes_t frames;
        snd_pcm_uframes_t periodsize;
        char *buffer;
        FILE *fp = fopen("play.wav", "rb");
        if(fp == NULL)
        return 0;
        fseek(fp, 100, SEEK_SET);
        /* Open PCM device for playback. */
        rc = snd_pcm_open(&handle, "default",
                        SND_PCM_STREAM_PLAYBACK, 0);//SND_PCM_NONBLOCK);
        if (rc < 0) {
        fprintf(stderr,
                "unable to open pcm device: %s/n",
                snd_strerror(rc));
        exit(1);
        }

        /* Allocate a hardware parameters object. */
        snd_pcm_hw_params_alloca(&params);

        /* Fill it in with default values. */
        snd_pcm_hw_params_any(handle, params);

        /* Set the desired hardware parameters. */

        /* Interleaved mode */
        snd_pcm_hw_params_set_access(handle, params,
                          SND_PCM_ACCESS_RW_INTERLEAVED);

        /* Signed 16-bit little-endian format */
        snd_pcm_hw_params_set_format(handle, params,
                                  SND_PCM_FORMAT_S16_LE);

        /* Two channels (stereo) */
        snd_pcm_hw_params_set_channels(handle, params, 1);

        /* 44100 bits/second sampling rate (CD quality) */
        val = 8000;
        snd_pcm_hw_params_set_rate_near(handle, params,
                                      &val, &dir);

        /* Set period size to 32 frames. */
        frames = 32;
        periodsize = frames * 2;
        rc = snd_pcm_hw_params_set_buffer_size_near(handle, params, &periodsize);
        if (rc < 0) 
        {
             printf("Unable to set buffer size %li : %s/n", frames * 2, snd_strerror(rc));
             
        }
              periodsize /= 2;
        rc = snd_pcm_hw_params_set_period_size_near(handle, params, &periodsize, 0);
        if (rc < 0) 
        {
            printf("Unable to set period size %li : %s/n", periodsize,  snd_strerror(rc));
        }
        
        /* Write the parameters to the driver */
        rc = snd_pcm_hw_params(handle, params);
        if (rc < 0) {
        fprintf(stderr,
                "unable to set hw parameters: %s/n",
                snd_strerror(rc));
        }

        /* Use a buffer large enough to hold one period */
        snd_pcm_hw_params_get_period_size(params, &frames, &dir);
                                    
        size = frames * 2; /* 2 bytes/sample, 2 channels */
        buffer = (char *) malloc(size);
        fprintf(stderr,
                "size = %d/n",
                size);
        /* We want to loop for 5 seconds */
        //snd_pcm_hw_params_get_period_time(params,
        //                                &val, &dir);
        //snd_pcm_start(handle);
        while (1) 
        {
            rc = fread(buffer, 1, size, fp);
            if(rc == 0) 
            {
                  fprintf(stderr, "end of file on input/n");
                  break;
            } 
            else if (rc != size) 
            {
            }

            while(rc = snd_pcm_writei(handle, buffer, frames)<0)
            {
                usleep(2000);
                if (rc == -EPIPE)
                {
                      /* EPIPE means underrun */
                      fprintf(stderr, "underrun occurred/n");
                      snd_pcm_prepare(handle);
                } 
                else if (rc < 0) 
                {
                      fprintf(stderr,
                          "error from writei: %s/n",
                          snd_strerror(rc));
                }  
            }
            //snd_pcm_drain(handle);
            //usleep(7000);
            //printf("#/n");
        }
        snd_pcm_drain(handle);
        snd_pcm_close(handle);
        free(buffer);
        fclose(fp);
        return 0;
    }