🚛 first commit

privateip.go

@@ -0,0 +1,65 @@
+package snowflake
+
+import (
+	"errors"
+	"net"
+)
+
+// PrivateIPToMachineID convert private ip to machine id.
+// From https://github.com/sony/sonyflake/blob/master/sonyflake.go
+func PrivateIPToMachineID() uint16 {
+	ip, err := lower16BitPrivateIP()
+	if err != nil {
+		return 0
+	}
+
+	return ip
+}
+
+//--------------------------------------------------------------------
+// private function defined.
+//--------------------------------------------------------------------
+
+func privateIPv4() (net.IP, error) {
+	as, err := net.InterfaceAddrs()
+	if err != nil {
+		return nil, err
+	}
+
+	for _, a := range as {
+		ipnet, ok := a.(*net.IPNet)
+		if !ok || ipnet.IP.IsLoopback() {
+			continue
+		}
+
+		ip := ipnet.IP.To4()
+		if isPrivateIPv4(ip) {
+			return ip, nil
+		}
+	}
+
+	return nil, errors.New("no private ip address")
+}
+
+func isPrivateIPv4(ip net.IP) bool {
+	return ip != nil &&
+		(ip[0] == 10 || ip[0] == 172 && (ip[1] >= 16 && ip[1] < 32) || ip[0] == 192 && ip[1] == 168)
+}
+
+func lower16BitPrivateIP() (uint16, error) {
+	ip, err := privateIPv4()
+	if err != nil {
+		return 0, err
+	}
+
+	// Snowflake macnineID max length is 10, max value is 1023
+	// If ip[2] > 3, return ip[2] + ip[3], but:
+	// 10.21.5.211 => return 5 + 211 = 216
+	// 10.21.4.212 => return 4 + 212 = 216
+	// need help if you can do this.
+	if ip[2] > 3 {
+		return uint16(ip[2] + ip[3]), nil
+	}
+
+	return uint16(ip[2])<<8 + uint16(ip[3]), nil
+}