골롱 절편 메커니즘을 깊이 이해하다

package main

import (
    "fmt"
    "unsafe"
)

type Slice struct {
    ptr unsafe.Pointer // Array pointer
    len int            // slice length
    cap int            // slice capacity
}

//         ，      int   
// 32  int length = 4
// 64  int length = 8
var intLen = int(unsafe.Sizeof(int(0)))

func main() {
    s := make([]int, 10, 20)

    //        slice memory    
    if intLen == 4 { // 32 
        m := *(*[4 + 4*2]byte)(unsafe.Pointer(&s))
        fmt.Println("slice memory:", m)
    } else { // 64  
        m := *(*[8 + 8*2]byte)(unsafe.Pointer(&s))
        fmt.Println("slice memory:", m)
    }

    //  slice        Slice struct
    slice := (*Slice)(unsafe.Pointer(&s))
    fmt.Println("slice struct:", slice)
    fmt.Printf("ptr:%v len:%v cap:%v 
", slice.ptr, slice.len, slice.cap)
    fmt.Printf("golang slice len:%v cap:%v 
", len(s), cap(s))

    s[0] = 0
    s[1] = 1
    s[2] = 2

    //       
    arr := *(*[3]int)(unsafe.Pointer(slice.ptr))
    fmt.Println("array values:", arr)

    //    slice   len
    slice.len = 15
    fmt.Println("Slice len: ", slice.len)  
    fmt.Println("golang slice len: ", len(s))  
}

//   cap  ，  array ptr      
s := make([]int, 1)

fmt.Printf("len:%d cap: %d array ptr: %v 
", len(s), cap(s), *(*unsafe.Pointer)(unsafe.Pointer(&s)))

for i := 0; i < 5; i++ {
    s = append(s, i)
    fmt.Printf("len:%d cap: %d array ptr: %v 
", len(s), cap(s), *(*unsafe.Pointer)(unsafe.Pointer(&s)))
}

fmt.Println("Array:", s)