You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: syscall_darwin.go
    path of file: ./repos/darktile/vendor/golang.org/x/sys/unix
    
    the code of the file until where you have to start completion: // Copyright 2009,2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-sty
    
func xattrPointer(dest []byte) *byte {
	// It's only when dest is set to NULL that the OS X implementations of
	// getxattr() and listxattr() return the current sizes of the named attributes.
	// An empty byte array is not sufficient. To maintain the same behaviour as the
	// linux implementation, we wrap around the system calls and pass in NULL when
	// dest is empty.
	var destp *byte
	if len(dest) > 0 {
		destp = &dest[0]
	}
	return destp
}