范围/ CIDR中的其余IP

Question

I would like to find the remaining IPs in a range (CIDR). For example:

prefixLen, bits := n.Mask.Size()
return 1 << (uint64(bits) - uint64(prefixLen)), nil

This return the # of IPs in the range where n is *net.IPNet. But say if I have few addresses that are already given out and want to know how many are left 'starting' from some IP addresses, how can I do it?

Answer 1

Here's something you could do

package main

import (
    "fmt"
    "net"

)
func inet_aton(ip string) uint32 {
var rv uint32
b := net.ParseIP(ip).To4()
rv=uint32(b[0]) << 24
rv=rv+uint32(b[1]) << 16
rv=rv+uint32(b[2]) << 8
rv=rv+uint32(b[3])
return rv
}

func main() {
    start := inet_aton("192.168.0.1")   //192.168.2.0/20 start
    fin := inet_aton("192.168.15.255")  //ditto end
    here := inet_aton("192.168.15.248") //current allocation

    fmt.Printf("you have %d remaining
",(fin-start) - (here-start))
}