server: Sort ips based on their last octet value. (#2198)

host-to-ip.go

@@ -0,0 +1,47 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package main
+
+import (
+	"net"
+	"sort"
+)
+
+// byLastOctet implements sort.Interface used in sorting a list
+// of ip address by their last octet value.
+type byLastOctet []net.IP
+
+func (n byLastOctet) Len() int      { return len(n) }
+func (n byLastOctet) Swap(i, j int) { n[i], n[j] = n[j], n[i] }
+func (n byLastOctet) Less(i, j int) bool {
+	return []byte(n[i].To4())[3] < []byte(n[j].To4())[3]
+}
+
+// getIPsFromHosts - returns a reverse sorted list of ips based on the last octet value.
+func getIPsFromHosts(hosts []string) (ips []net.IP) {
+	for _, host := range hosts {
+		ips = append(ips, net.ParseIP(host))
+	}
+	// Reverse sort ips by their last octet.
+	sort.Sort(sort.Reverse(byLastOctet(ips)))
+	return ips
+}
+
+// getHostToIP - parses a host string into net.IP value.
+func getHostToIP(host string) net.IP {
+	return net.ParseIP(host)
+}