golang: slice append and cap

slice-append-cap.go

package main

import "fmt"


func main() {

	slice := []int{1}
	
	fmt.Printf("%v , len: %v , cap: %v\n", &slice[0], len(slice), cap(slice))
	
	oldCap := cap(slice)
	
	for i := 0; i<10000; i++ {
		slice = append(slice, i)
		if cap(slice) > oldCap {
			fmt.Printf("%v , len: %v , cap: %v\n", &slice[0], len(slice), cap(slice))
			oldCap = cap(slice)
		}
	}
}

output

0xc420016080 , len: 1 , cap: 1
0xc4200160b0 , len: 2 , cap: 2
0xc420018260 , len: 3 , cap: 4
0xc420012100 , len: 5 , cap: 8
0xc42008e000 , len: 9 , cap: 16
0xc420090000 , len: 17 , cap: 32
0xc420092000 , len: 33 , cap: 64
0xc420094000 , len: 65 , cap: 128
0xc420096000 , len: 129 , cap: 256
0xc420098000 , len: 257 , cap: 512
0xc42009a000 , len: 513 , cap: 1024
0xc42009c000 , len: 1025 , cap: 1280
0xc4200a6000 , len: 1281 , cap: 1696
0xc4200b0000 , len: 1697 , cap: 2304
0xc4200c2000 , len: 2305 , cap: 3072
0xc4200c8000 , len: 3073 , cap: 4096
0xc4200d0000 , len: 4097 , cap: 5120
0xc4200da000 , len: 5121 , cap: 7168
0xc4200e8000 , len: 7169 , cap: 9216
0xc4200fa000 , len: 9217 , cap: 12288