fn writeAllSync(sync: *CancelRegion.Sync, fd: fd_t, buffer: []const u8) File.Writer.Error!void
fn writeAllSync(sync: *CancelRegion.Sync, fd: fd_t, buffer: []const u8) File.Writer.Error!void { var index: usize = 0; while (buffer.len - index != 0) index += try writeSync(sync, fd, buffer[index..]); }