iplist: Double performance of parsing line

iplist/iplist.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"fmt"
 	"net"
-	"regexp"
 	"sort"
 	"strings"
 )
@@ -50,24 +49,19 @@ func (me *IPList) Lookup(ip net.IP) (r *Range) {
 	return
 }
 
-var p2pBlocklistLineRe = regexp.MustCompile(`(.*):([\d.]+)-([\d.]+)`)
-
 // Parse a line of the PeerGuardian Text Lists (P2P) Format. Returns !ok but
 // no error if a line doesn't contain a range but isn't erroneous, such as
 // comment and blank lines.
 func ParseBlocklistP2PLine(l string) (r Range, ok bool, err error) {
 	l = strings.TrimSpace(l)
-	if l == "" || strings.HasPrefix(l, "#") {
+	if len(l) == 0 || strings.HasPrefix(l, "#") {
 		return
 	}
-	sms := p2pBlocklistLineRe.FindStringSubmatch(l)
-	if sms == nil {
-		err = fmt.Errorf("error parsing %q", l)
-		return
-	}
-	r.Description = sms[1]
-	r.First = net.ParseIP(sms[2])
-	r.Last = net.ParseIP(sms[3])
+	colon := strings.IndexByte(l, ':')
+	hyphen := strings.IndexByte(l[colon+1:], '-') + colon + 1
+	r.Description = l[:colon]
+	r.First = net.ParseIP(l[colon+1 : hyphen])
+	r.Last = net.ParseIP(l[hyphen+1:])
 	if r.First == nil || r.Last == nil {
 		return
 	}