39 lines
878 B
Go
39 lines
878 B
Go
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package cidr
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import (
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"fmt"
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"math/big"
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"net"
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)
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func ipToInt(ip net.IP) (*big.Int, int) {
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val := &big.Int{}
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val.SetBytes([]byte(ip))
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if len(ip) == net.IPv4len {
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return val, 32
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} else if len(ip) == net.IPv6len {
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return val, 128
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} else {
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panic(fmt.Errorf("Unsupported address length %d", len(ip)))
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}
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}
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func intToIP(ipInt *big.Int, bits int) net.IP {
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ipBytes := ipInt.Bytes()
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ret := make([]byte, bits/8)
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// Pack our IP bytes into the end of the return array,
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// since big.Int.Bytes() removes front zero padding.
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for i := 1; i <= len(ipBytes); i++ {
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ret[len(ret)-i] = ipBytes[len(ipBytes)-i]
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}
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return net.IP(ret)
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}
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func insertNumIntoIP(ip net.IP, num int, prefixLen int) net.IP {
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ipInt, totalBits := ipToInt(ip)
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bigNum := big.NewInt(int64(num))
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bigNum.Lsh(bigNum, uint(totalBits-prefixLen))
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ipInt.Or(ipInt, bigNum)
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return intToIP(ipInt, totalBits)
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}
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