almost done ackshually

netsplit/funcs_vlsmsplitter.go

@@ -0,0 +1,97 @@
+package netsplit
+
+import (
+	"go4.org/netipx"
+	"net/netip"
+	"sort"
+)
+
+// Split splits the network defined in a VLSMSplitter alongside its configuration and performs the subnetting.
+func (v *VLSMSplitter) Split() (nets []*netip.Prefix, remaining *netipx.IPSet, err error) {
+
+	var ok bool
+	var pfxLen int
+	var pfxLen8 uint8
+	var base netip.Prefix
+	var sub netip.Prefix
+	var subPtr *netip.Prefix
+	var ipsb *netipx.IPSetBuilder = new(netipx.IPSetBuilder)
+
+	if err = ValidateSizes(v.network, v.PrefixLengths...); err != nil {
+		return
+	}
+
+	/*
+		I thought about using the following:
+
+			* https://pkg.go.dev/net/netip
+			* https://pkg.go.dev/github.com/sacloud/packages-go/cidr
+			* https://pkg.go.dev/github.com/projectdiscovery/mapcidr
+			* https://pkg.go.dev/github.com/EvilSuperstars/go-cidrman
+
+		But, as I expected, netipx ftw again.
+	*/
+
+	if v == nil || v.PrefixLengths == nil || len(v.PrefixLengths) == 0 || v.BaseSplitter == nil || v.network == nil {
+		return
+	}
+
+	sort.SliceStable(
+		v.PrefixLengths,
+		func(i, j int) (isBefore bool) { // We use a reverse sorting by default so we get larger prefixes at the beginning.
+			if v.Ascending {
+				isBefore = v.PrefixLengths[i] > v.PrefixLengths[j]
+			} else {
+				isBefore = v.PrefixLengths[i] < v.PrefixLengths[j]
+			}
+			return
+		},
+	)
+
+	pfxLen, _ = v.network.Mask.Size()
+	pfxLen8 = uint8(pfxLen)
+
+	if base, ok = netipx.FromStdIPNet(v.network); !ok {
+		err = ErrBadBoundary
+		return
+	}
+	if !base.IsValid() {
+		err = ErrBadBoundary
+		return
+	}
+
+	ipsb.AddPrefix(base)
+	if remaining, err = ipsb.IPSet(); err != nil {
+		return
+	}
+
+	for _, size := range v.PrefixLengths {
+		if size < pfxLen8 {
+			err = &SplitErr{
+				Wrapped:            ErrBigPrefix,
+				Nets:               nets,
+				Remaining:          remaining,
+				LastSubnet:         &sub,
+				RequestedPrefixLen: size,
+			}
+			return
+		}
+
+		if sub, remaining, ok = remaining.RemoveFreePrefix(size); !ok {
+			err = &SplitErr{
+				Wrapped:            ErrNoNetSpace,
+				Nets:               nets,
+				Remaining:          remaining,
+				LastSubnet:         &sub,
+				RequestedPrefixLen: size,
+			}
+			return
+		}
+
+		subPtr = new(netip.Prefix)
+		*subPtr = sub
+		nets = append(nets, subPtr)
+	}
+
+	return
+}