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package cidr
import (
"fmt"
"net"
"github.com/apparentlymart/go-cidr/cidr"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/function"
"github.com/zclconf/go-cty/cty/gocty"
)
// SubnetFunc is a function that calculates a subnet address within a given
// IP network address prefix.
var SubnetFunc = function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "prefix",
Type: cty.String,
},
{
Name: "newbits",
Type: cty.Number,
},
{
Name: "netnum",
Type: cty.Number,
},
},
Type: function.StaticReturnType(cty.String),
Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
var newbits int
if err := gocty.FromCtyValue(args[1], &newbits); err != nil {
return cty.UnknownVal(cty.String), err
}
var netnum int
if err := gocty.FromCtyValue(args[2], &netnum); err != nil {
return cty.UnknownVal(cty.String), err
}
_, network, err := net.ParseCIDR(args[0].AsString())
if err != nil {
return cty.UnknownVal(cty.String), fmt.Errorf("invalid CIDR expression: %s", err)
}
// For portability with 32-bit systems where the subnet number will be
// a 32-bit int, we only allow extension of 32 bits in one call even if
// we're running on a 64-bit machine. (Of course, this is significant
// only for IPv6.)
if newbits > 32 {
return cty.UnknownVal(cty.String), fmt.Errorf("may not extend prefix by more than 32 bits")
}
newNetwork, err := cidr.Subnet(network, newbits, netnum)
if err != nil {
return cty.UnknownVal(cty.String), err
}
return cty.StringVal(newNetwork.String()), nil
},
})
// Subnet calculates a subnet address within a given IP network address prefix.
func Subnet(prefix, newbits, netnum cty.Value) (cty.Value, error) {
return SubnetFunc.Call([]cty.Value{prefix, newbits, netnum})
}
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