vendor/github.com/apparentlymart/go-cidr/cidr/wrangling.go

   1 package cidr
   2
   3 import (
   4         "fmt"
   5         "math/big"
   6         "net"
   7 )
   8
   9 func ipToInt(ip net.IP) (*big.Int, int) {
  10         val := &big.Int{}
  11         val.SetBytes([]byte(ip))
  12         if len(ip) == net.IPv4len {
  13                 return val, 32
  14         } else if len(ip) == net.IPv6len {
  15                 return val, 128
  16         } else {
  17                 panic(fmt.Errorf("Unsupported address length %d", len(ip)))
  18         }
  19 }
  20
  21 func intToIP(ipInt *big.Int, bits int) net.IP {
  22         ipBytes := ipInt.Bytes()
  23         ret := make([]byte, bits/8)
  24         // Pack our IP bytes into the end of the return array,
  25         // since big.Int.Bytes() removes front zero padding.
  26         for i := 1; i <= len(ipBytes); i++ {
  27                 ret[len(ret)-i] = ipBytes[len(ipBytes)-i]
  28         }
  29         return net.IP(ret)
  30 }
  31
  32 func insertNumIntoIP(ip net.IP, num int, prefixLen int) net.IP {
  33         ipInt, totalBits := ipToInt(ip)
  34         bigNum := big.NewInt(int64(num))
  35         bigNum.Lsh(bigNum, uint(totalBits-prefixLen))
  36         ipInt.Or(ipInt, bigNum)
  37         return intToIP(ipInt, totalBits)
  38 }