this is cool and all but the tables don't render properly

netsplit/funcs_subnetsplitter.go

@@ -1,14 +1,106 @@
 package netsplit
 
 import (
-	"go4.org/netipx"
+	`net`
 	"net/netip"
+
+	`github.com/projectdiscovery/mapcidr`
+	"go4.org/netipx"
 )
 
-// Split splits the network defined in a SubnetSplitter alongside its configuration and performs the subnetting.
+/*
+	Split splits the network defined in a SubnetSplitter alongside its configuration and performs the subnetting.
+	This strategy allows for splitting a network into exactly evenly sized specified number of subnets.
+
+	remaining may or may not be nil depending on if the specified number of subnets fit cleanly into the network boundaries.
+
+	An ErrNoNetSpace error will be returned if subnetting size exhaustion occurs before the specified number of subnets is reached
+	(but nets will be populated and remaining will contain any left over subnets).
+*/
 func (s *SubnetSplitter) Split() (nets []*netip.Prefix, remaining *netipx.IPSet, err error) {
 
-	// TODO
+	var ok bool
+	var pfxLen int
+	var base netip.Prefix
+	var sub netip.Prefix
+	var subPtr *netip.Prefix
+	var split []*net.IPNet
+	var ipsb *netipx.IPSetBuilder = new(netipx.IPSetBuilder)
+
+	if s == nil || s.BaseSplitter == nil || s.network == nil || s.NumberSubnets == 0 {
+		return
+	}
+
+	if base, ok = netipx.FromStdIPNet(s.network); !ok {
+		err = ErrBadBoundary
+		return
+	}
+	if !base.IsValid() {
+		err = ErrBadBoundary
+		return
+	}
+
+	if split, err = mapcidr.SplitIPNetIntoN(s.network, int(s.NumberSubnets)); err != nil {
+		return
+	}
+
+	for _, n := range split {
+		if sub, ok = netipx.FromStdIPNet(n); !ok {
+			// We bail early on this error.
+			err = &SplitErr{
+				Wrapped:            ErrBadBoundary,
+				Nets:               nets,
+				Remaining:          remaining,
+				LastSubnet:         subPtr,
+				RequestedPrefixLen: 0,
+			}
+			err = ErrBadBoundary
+			return
+		}
+		if sub.String() == base.String() {
+			continue
+		}
+		if pfxLen == 0 {
+			pfxLen = sub.Bits()
+			if nets == nil {
+				nets = make([]*netip.Prefix, 0)
+			}
+			subPtr = new(netip.Prefix)
+			*subPtr = sub
+			nets = append(nets, subPtr)
+		} else {
+			if sub.Bits() != pfxLen {
+				if err == nil {
+					// Return this err but don't return early; wait for the populate.
+					err = &SplitErr{
+						Wrapped:            ErrNoNetSpace,
+						Nets:               nets,
+						Remaining:          remaining,
+						LastSubnet:         subPtr,
+						RequestedPrefixLen: uint8(pfxLen),
+					}
+				}
+				ipsb.AddPrefix(sub)
+			} else {
+				subPtr = new(netip.Prefix)
+				*subPtr = sub
+				nets = append(nets, subPtr)
+			}
+		}
+	}
+
+	if remaining, err = ipsb.IPSet(); err != nil {
+		return
+	}
+
+	if len(nets) < int(s.NumberSubnets) {
+		err = &SplitErr{
+			Wrapped:   ErrNoNetSpace,
+			Nets:      nets,
+			Remaining: remaining,
+		}
+		return
+	}
 
 	return
 }