Function svn_utf_cstring_from_utf8_stringbuf 

pub unsafe extern "C" fn svn_utf_cstring_from_utf8_stringbuf(
    dest: *mut *const c_char,
    src: *const svn_stringbuf_t,
    pool: *mut apr_pool_t,
) -> *mut svn_error_t

Set @a *dest to a natively-encoded C string from utf8 stringbuf @a src; allocate @a *dest in @a pool.