增加configutils/ParseCIDR()函数

pkg/configutils/ip.go

@@ -25,6 +25,28 @@ func IP2Long(ip string) uint64 {
 	return uint64(binary.BigEndian.Uint32(s.To4()))
 }
 
+// ParseCIDR 计算CIDR最大值
+func ParseCIDR(cidr string) (ipFrom string, ipTo string, err error) {
+	_, ipNet, err := net.ParseCIDR(cidr)
+	if err != nil {
+		return "", "", err
+	}
+	ipFrom = ipNet.IP.String()
+Loop:
+	for i := len(ipNet.Mask) - 1; i >= 0; i-- {
+		for j := 7; j >= 0; j-- {
+			var m = ipNet.Mask[i] >> (7 - j) & 1 // 读取某位bit
+			if m == 0 {
+				ipNet.IP[i] |= 1 << j // 将此位置为1
+			} else {
+				break Loop
+			}
+		}
+	}
+	ipTo = ipNet.IP.String()
+	return
+}
+
 // QuoteIP 为IPv6加上括号
 func QuoteIP(ip string) string {
 	if len(ip) == 0 {

pkg/configutils/ip_test.go

@@ -0,0 +1,11 @@
+// Copyright 2021 Liuxiangchao iwind.liu@gmail.com. All rights reserved.
+
+package configutils
+
+import "testing"
+
+func TestParseCIDR(t *testing.T) {
+	t.Log(ParseCIDR("192.168.1.1/32"))
+	t.Log(ParseCIDR("192.168.1.1/24"))
+	t.Log(ParseCIDR("192.168.1.1/16"))
+}