how does Audacity uses SoundTouch?

I don’t know if it’s appropriate to post here, but I am trying to use soundtouch in one of my projects, and I can’t seem to get it working.

My question specifically is: soundtouch’s putSamples functions takes a float*, but when I read the audio file, I read it into a char* (a byte at a time reading). is it ok to memcpy the char* into a float*?

I am wondering how Audacity made it work?