Golang 指针(unsafe.Pointer、uintptr)

package mainimport ("fmt""unsafe"
)func main() {
    //指针//符号： 取址& 取值*//go指针只能读，不能修改指针的值addr := "沙河"addrP := &addrfmt.Printf("类型：%T，变量值：%v,指向的值：%v \n", addrP, addrP, *addrP)//类型：*string，变量值：0xc00004e230,指向的值：沙河fmt.Println("=============")//修改指针的值：var arr = []int32{
    11, 22, 33}fmt.Println("1.获得arr[0]的指针：")var ptr = &arr[0]fmt.Printf("&arr[0]的类型是：%T,值是：%v\n", ptr, ptr) //*int32 0xc0000140d0fmt.Println("2.将*int32指针转换成unsafe.Pointer类型的指针：")ptr_first_unsafe_point := unsafe.Pointer(ptr)fmt.Printf("ptr_first_unsafe_point的类型是：%T,值是：%v\n", ptr_first_unsafe_point, ptr_first_unsafe_point) //unsafe.Pointer 0xc0000140d0fmt.Println("3.将unsafe.Pointer指针转换成uintptr类型的指针：")ptr_uintptr_first_unsafe_point := uintptr(ptr_first_unsafe_point)fmt.Printf("ptr_uintptr_first_unsafe_point的类型是：%T,值是：%v\n", ptr_uintptr_first_unsafe_point, ptr_uintptr_first_unsafe_point) //uintptr 824633802960fmt.Println("4.将uintptr指针修改，值加4：")//int32 一个数的大小对应 4个字节，所以加4获得数组的第二个元素：22；ptr_uintptr_first_unsafe_point += 4fmt.Printf("ptr_uintptr_first_unsafe_point指针值是%v\n", ptr_uintptr_first_unsafe_point) //824633802964fmt.Println("5.将uintptr指针转换成unsafe.Pointer类型的指针：")ptr_uintptr_second_unsafe_point := unsafe.Pointer(ptr_uintptr_first_unsafe_point)fmt.Printf("ptr_uintptr_second_unsafe_point的类型是：%T,值是：%v\n", ptr_uintptr_second_unsafe_point, ptr_uintptr_second_unsafe_point) //unsafe.Pointer 0xc0000140d4fmt.Println("6.将unsafe.Pointer指针转换成*int32类型的指针：")ptr_after_change := (*int32)(ptr_uintptr_second_unsafe_point)fmt.Printf("ptr_after_change指针值是%v\n", ptr_after_change)     //0xc0000140d4fmt.Printf("ptr_after_change指针指向的值是%v\n", *ptr_after_change) //22/* 结果：1.获得arr[0]的指针：&arr[0]的类型是：*int32,值是：0xc0000140d02.将*int32指针转换成unsafe.Pointer类型的指针：ptr_first_unsafe_point的类型是：unsafe.Pointer,值是：0xc0000140d03.将unsafe.Pointer指针转换成uintptr类型的指针：ptr_uintptr_first_unsafe_point的类型是：uintptr,值是：8246338029604.将uintptr指针修改，值加4：ptr_uintptr_first_unsafe_point指针值是8246338029645.将uintptr指针转换成unsafe.Pointer类型的指针：ptr_uintptr_second_unsafe_point的类型是：unsafe.Pointer,值是：0xc0000140d46.将unsafe.Pointer指针转换成*int32类型的指针：ptr_after_change指针值是0xc0000140d4ptr_after_change指针指向的值是22*//*- unsafe.Pointer只是单纯的通用指针类型，用于转换不同类型指针，它不可以参与指针运算；- 而uintptr是用于指针运算的，GC 不把 uintptr 当指针，也就是说 uintptr 无法持有对象， uintptr 类型的目标会被回收；- unsafe.Pointer 可以和 普通指针 进行相互转换；- unsafe.Pointer 可以和 uintptr 进行相互转换。*/
}