Go语言普通指针unsafe.Pointer uintpt之间的关系及指针运算

#include <stdio.h>
const int MAX = 3;
int main ()
{
   int  var[] = {10, 100, 200};
   int  i, *ptr;
   /* 指针中的数组地址 */
   ptr = var;
   for ( i = 0; i < MAX; i++)
   {
      printf("存储地址：var[%d] = %p\n", i, ptr );
      printf("存储值：var[%d] = %d\n", i, *ptr );
      /* 直接对指针做++操作，指向下一个位置 */
      ptr++;
   }
   return 0;
}

#include <stdio.h>
int findMin(int *arr, int length) {
    int min = *arr;
    for (int i = 0; i <= length; i++) {  // 注意这里是 i <= length，而不是 i < length
        printf("i=%d v=%d\n", i, *(arr+i));
        if (*(arr + i) < min) {
            min = *(arr + i);
        }
    }
    return min;
}
int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int length = sizeof(arr) / sizeof(arr[0]);
    printf("Min value is: %d\n", findMin(arr, length));
    return 0;
}

a := 10
var p *int = &a
p = p + 1

*T <-> unsafe.Pointer <-> uintptr

func main() {
    a := 10
    var b *int
    b = &a
    fmt.Printf("a is %T, a=%v\n", a, a)
    fmt.Printf("b is %T, b=%v\n", b, b)
    p := unsafe.Pointer(b)
    fmt.Printf("p is %T, p=%v\n", p, p)
    uptr := uintptr(p)
    fmt.Printf("uptr is %T, uptr=%v\n", uptr, uptr)
}

type People struct {
    age    int32
    height int64
    name   string
}
people := &People{}
fmt.Println(people)
// 将 people 普通指针转成 unsafe.Pointer 再转为 uintptr
// 后面再加上 height 字段相对于结构体本身的偏移量，就得到了 height 的地址的 uintptr 值
// 再将 height 的 uintptr 值转成 unsafe.Pointer 赋值给 height 变量
// 所以现在 height 的类型是 unsafe.Pointer
height := unsafe.Pointer(uintptr(unsafe.Pointer(people)) + unsafe.Offsetof(people.height))
fmt.Printf("people addr is %v\n", unsafe.Pointer(people))
fmt.Printf("height is %T\n", height)
fmt.Printf("height addr is %v\n", height)
println("---")
// 使用类型转换，将 unsafe.Pointer 类型的 height 转换成 *int 指针
// 再通过最前面的 * 解引用，修改其值 身高2米26
*((*int)(height)) = 226
fmt.Println(people)
// 同样的操作可以修改年龄和名字
age := unsafe.Pointer(uintptr(unsafe.Pointer(people)) + unsafe.Offsetof(people.age))
*((*int)(age)) = 18
name := unsafe.Pointer(uintptr(unsafe.Pointer(people)) + unsafe.Offsetof(people.name))
*((*string)(name)) = "小明"
fmt.Println(people)

package main
import (
    "fmt"
    "unsafe"
)
func main() {
    // 假设我们有一个字节切片，并且我们知道它是由浮点数表示的
    byteSlice := []byte{0, 0, 0, 0, 0, 0, 240, 63} // 1.0 的 IEEE-754 表示
    // 使用 unsafe 把字节切片转换为浮点数切片
    floatSlice := (*[1]float64)(unsafe.Pointer(&byteSlice[0]))
    fmt.Println(floatSlice)
}