Go 指针、uintptr、unsafe.Pointer之间如何转换

	a := 10
	var b *int  //int类型指针
	b = &a
	fmt.Println("a=", a)  // a=10
	fmt.Println("b=", b)  // b=0xc000225530 输出的是a的地址
	fmt.Println("c=", *b) // c=10  对a的地址进行取值

package builtin

//uintptr is an integer type that is large enough to hold the bit pattern of any pointer.
//uintptr是一个能足够容纳指针位数大小的整数类型
type uintptr uintptr

type Pointer *ArbitraryType

type ArbitraryType int

==unsafe包的几个函数==

//返回一个变量占用的内存字节数
func Sizeof(x ArbitraryType) uintptr

//返回结构体某个字段的地址相对于此结构体起始地址的偏移量
func Offsetof(x ArbitraryType) uintptr

//返回对齐系数
func Alignof(x ArbitraryType) uintptr

	a := int64(100)
	var ptr *int
	ptr = (*int)(unsafe.Pointer(&a))
	fmt.Printf("%d\n", *ptr) 
	//输出100 如果是int32输出一个很大值
	

    type People struct {
	    age    int32
	    height int64
    }
    var p = &People
	height := unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Offsetof(p.height))
	*((*int)(height)) = 100 //将height的值改为100
	//uintptr(unsafe.Pointer(p)) 获取了 w 的指针起始值
    //unsafe.Offsetof(w.p) 获取 b 变量的偏移量

    var p = &People
	height := unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Offsetof(p.height))
	*((*int)(height)) = 100 //将height的值改为100