GoLang中地址的按位XOR

Question

I was trying to implement the XOR Linked List in Go where I had to store the XORed address. In C/C++ it's quite simple

(*struct_type)(([unsigned] int)nodeA ^ ([unsigned] int)nodeB)

I tried a similar approach in Go. I had a struct named Node with two nodes nodeA and nodeB. To get this I tried the following ways:

*Node(uint(nodeA) ^ uint(nodeB))

Which gave me an error saying, can't convert type Node to uint. Another way I tried, which I was sure woundn't work, was

nodeA ^ nodeB

Is there a way to parse the address to int type, XOR them and then re-parse them into Node address? Or does Go provide a simple solution to this that I'm not aware of?

Answer 1

Use unsafe.Pointer for pointer arithmetic:

a := &T{}
b := &T{}
x := uintptr(unsafe.Pointer(a)) ^ uintptr(unsafe.Pointer(b))
y := (*T)(unsafe.Pointer(uintptr(unsafe.Pointer(a)) ^ x))
fmt.Println(b == y)  // prints true

The GC uses pointers to track memory. If the code is rewritten to

a := &T{}
b := &T{}
x := uintptr(unsafe.Pointer(a)) ^ uintptr(unsafe.Pointer(b))
b = nil // clear all pointers to struct
b = (*T)(unsafe.Pointer(uintptr(unsafe.Pointer(a)) ^ x))

then it's possible for the GC to collect the struct pointed to by b before the last assignment to b.

It's not possible to implement a safe XOR list in Go because the GC can collect the elements.

Don't do this.