def src_callback_read(state, ratio, frames, data):
data_ptr = ffi.cast('<STR_LIT>', ffi.from_buffer(data))<EOL>return _lib.src_callback_read(state, ratio, frames, data_ptr)<EOL>
Read up to `frames` worth of data using the callback API.

    Returns
    -------
    frames : int
        Number of frames read or -1 on error.