在 golang 中将字符串转换为 *uint64

Question

Assume there is a string holding the address of an uint64 type variable, can we parse this address back to an *uint64 ?

For example:

i := uint64(23473824)
ip := &i
str := fmt.Sprintf("%v", ip)

u, _ := strconv.ParseUint(str, 0, 64)

u is uint64 . How to get pointer out of this value?

Playground link: https://play.golang.org/p/1KXFQcozRk

Answer 1

It is as simple as:

number, err := strconv.ParseUint(string("90"), 10, 64)

then do some error checking, hope it helps.

Answer 2

You can do it with

 ip = (*uint64)(unsafe.Pointer(uintptr(u)))

playground link

Albeit I don't know what guarantees Go gives you about the validity of such a pointer, nor can I think of any use case where this code should be used..

Answer 3

Based on nos answer .

Although it is technically possible there are reasons not to trust the code you wrote. Garbage collection will use the memory you point to (with string).

Take a look at result of the following code.

package main

import(
    "fmt"
    "strconv"
    "reflect"
    "unsafe"
)

func produce() string {
    i := uint64(23473824)
    ip := &i
    str := fmt.Sprintf("%v", ip)
    fmt.Println(i, ip, str)
    return str
}

func main() {
    str := produce()

    for i := 0; i < 10; i++ {
         x := make([]int, 1024*1024)
         x[0] = i
    }        

    u, _ := strconv.ParseUint(str, 0, 64) 

    ip := (*uint64)(unsafe.Pointer(uintptr(u)))
    fmt.Println(ip,*ip, reflect.TypeOf(u)) // u is uint64, how to get pointer out of this value?
}

https://play.golang.org/p/85XOhsMTf3