Golang: what's a slice?

README.md

What's In a Slice?

Running this script:

$ go run main.go
As slice: [147 801]
As intSlice: {start:0xc000014260 len:2 cap:4}
s[0] = 147
s[1] = 801
s[2] = 0
s[3] = 0
s[4] = 7805710596722160449

main.go

package main

import (
	"fmt"
	"unsafe"
)

type intSlice struct {
	start *int
	len   int
	cap   int
}

func main() {
	s := make([]int, 0, 4)
	s = append(s, 147, 801)
	fmt.Printf("As slice: %+v\n", s)

	p := unsafe.Pointer(&s)
	t := (*intSlice)(p)
	fmt.Printf("As intSlice: %+v\n", *t)

	curr := t.start
	sz := unsafe.Sizeof(s[0])

	maxIndex := 4
	for i := 0; i < maxIndex; i++ {
		fmt.Printf("s[%d] = %+v\n", i, *curr)
		curr = (*int)(unsafe.Pointer(uintptr(unsafe.Pointer(curr)) + sz))
	}
	fmt.Printf("s[%d] = %+v\n", maxIndex, *curr)
}