Function fz_read_string 

pub unsafe extern "C" fn fz_read_string(
    ctx: *mut fz_context,
    stm: *mut fz_stream,
    buffer: *mut c_char,
    len: c_int,
)

Read a null terminated string from the stream into
a buffer of a given length. The buffer will be null terminated.
Throws on failure (including the failure to fit the entire
string including the terminator into the buffer).