C API, usage of function _snd_pcm_file_open()

["Jon Harald Øymyr" <joymyr@gmail.com>]

I had a look at the Spotify C API, and found that they were using the following code to output music from Spotify: snd_pcm_open(&h, dev, SND_PCM_STREAM_PLAYBACK, 0).

I want use this function instead: 
int _snd_pcm_file_open(snd_pcm_t **pcmp, const char *name, snd_config_t *root, snd_config_t *conf, snd_pcm_stream_t stream, int mode)

The function is found here: 
http://www.alsa-project.org/alsa-doc/alsa-lib/pcm__file_8c.html#94d0dc725e55a974d792e16f8abdc60a

I'm not able to find anything in the documentation explaining what the two parameters snd_config_t *root and snd_config_t *conf is.

What I'm trying to achieve is to write the stream to a file, and then read it from another application. But it would be even better if I could make the C application write to standard output.

Can anybody help me with this?
I'm not very experienced with either C programming or streaming, but I would really like to make this work.