slice shrink

main.go

package main

import (
	"fmt"
)

func main() {
	array := make([]int, 0, 0)
	for i := 0; i < 1000; i++ {
		array = append(array, i)
		if i%100 == 0 {
			fmt.Printf("ptr=%p len=%-3d cap=%d\n", &array[0], len(array), cap(array))
		}
	}
	array = array[:0]
	fmt.Println("-------")
	for i := 0; i < 1000; i++ {
		array = append(array, i)
		if i%100 == 0 {
			fmt.Printf("ptr=%p len=%-3d cap=%d\n", &array[0], len(array), cap(array))
		}
	}
}

Execution Result:

>slice-shrink.exe
ptr=0xc042050058 len=1   cap=1
ptr=0xc042088000 len=101 cap=128
ptr=0xc04208c000 len=201 cap=256
ptr=0xc04208e000 len=301 cap=512
ptr=0xc04208e000 len=401 cap=512
ptr=0xc04208e000 len=501 cap=512
ptr=0xc042090000 len=601 cap=1024
ptr=0xc042090000 len=701 cap=1024
ptr=0xc042090000 len=801 cap=1024
ptr=0xc042090000 len=901 cap=1024
-------
ptr=0xc042090000 len=1   cap=1024
ptr=0xc042090000 len=101 cap=1024
ptr=0xc042090000 len=201 cap=1024
ptr=0xc042090000 len=301 cap=1024
ptr=0xc042090000 len=401 cap=1024
ptr=0xc042090000 len=501 cap=1024
ptr=0xc042090000 len=601 cap=1024
ptr=0xc042090000 len=701 cap=1024
ptr=0xc042090000 len=801 cap=1024
ptr=0xc042090000 len=901 cap=1024