Function svn_utf_stringbuf_to_utf8 

pub unsafe extern "C" fn svn_utf_stringbuf_to_utf8(
    dest: *mut *mut svn_stringbuf_t,
    src: *const svn_stringbuf_t,
    pool: *mut apr_pool_t,
) -> *mut svn_error_t

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