Fixed wrong value returned by CIDRToIPv6 function

see: ip2location/ip2location-java@6ff27d6

README.md

@@ -30,7 +30,7 @@ Or download the zip file in the warehouse and decompress it by yourself.
 <dependency>
     <groupId>net.renfei</groupId>
     <artifactId>ip2location</artifactId>
-    <version>1.2.0</version>
+    <version>1.2.1</version>
 </dependency>
 ```
 

README_zh.md

@@ -30,7 +30,7 @@
 <dependency>
     <groupId>net.renfei</groupId>
     <artifactId>ip2location</artifactId>
-    <version>1.2.0</version>
+    <version>1.2.1</version>
 </dependency>
 ```
 

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>net.renfei</groupId>
     <artifactId>ip2location</artifactId>
-    <version>1.2.0</version>
+    <version>1.2.1</version>
     <name>ip2location</name>
     <url>http://www.renfei.net</url>
     <description>IP2Location Java Component enables applications to get info from IP address such as the visitor’s country, region, city, latitude, longitude, ZIP code, ISP name, domain name, time zone, connection speed, IDD code, area code, weather station code, weather station name, MCC, MNC, mobile brand name, elevation and usage type.</description>
@@ -57,6 +57,14 @@
         <maven.compiler.target>8</maven.compiler.target>
     </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.13.0</version>
+        </dependency>
+    </dependencies>
+
     <build>
         <plugins>
             <plugin>

src/main/java/net/renfei/ip2location/IPTools.java

@@ -1,5 +1,7 @@
 package net.renfei.ip2location;
 
+import org.apache.commons.lang3.StringUtils;
+
 import java.math.BigInteger;
 import java.net.InetAddress;
 import java.net.Inet4Address;
@@ -388,8 +390,7 @@ public List<String> IPv6ToCIDR(String IPFrom, String IPTo) throws UnknownHostExc
 
         } while (ipFromBin.compareTo(ipToBin) < 0);
 
-        for (Map.Entry<String, Integer>
-                entry : networks.entrySet()) {
+        for (Map.Entry<String, Integer> entry : networks.entrySet()) {
             result.add(CompressIPv6(BinaryToIP(entry.getKey())) + "/" + entry.getValue());
         }
 
@@ -464,33 +465,26 @@ public String[] CIDRToIPv6(String CIDR) throws UnknownHostException {
         ip = arr[0];
         prefix = Integer.parseInt(arr[1]);
 
-        String hexStartAddress = ExpandIPv6(ip).replaceAll(":", "");
-        String hexEndAddress = hexStartAddress;
+        String[] parts = ExpandIPv6(ip).split("\\:");
 
-        int bits = 128 - prefix;
-        int x;
-        String y;
-        int pos = 31;
-        List<Integer> values;
-        char[] tmp;
-        while (bits > 0) {
-            values = Arrays.asList(4, bits);
-            x = Integer.parseInt(String.valueOf(hexEndAddress.charAt(pos)), 16);
-            y = String.format("%x", (x | (int) (Math.pow(2, Collections.min(values)) - 1))); // single hex char
-
-            // replace char
-            tmp = hexEndAddress.toCharArray();
-            tmp[pos] = y.charAt(0);
-            hexEndAddress = String.valueOf(tmp);
-
-            bits -= 4;
-            pos -= 1;
+        String bitStart = StringUtils.repeat('1', prefix) + StringUtils.repeat('0', 128 - prefix);
+        String bitEnd = StringUtils.repeat('0', prefix) + StringUtils.repeat('1', 128 - prefix);
+
+        int chunkSize = 16;
+
+        String[] floors = bitStart.split("(?<=\\G.{" + chunkSize + "})");
+        String[] ceilings = bitEnd.split("(?<=\\G.{" + chunkSize + "})");
+
+        List<String> startIP = new ArrayList(8);
+        List<String> endIP = new ArrayList(8);
+
+        for (int x = 0; x < 8; x++) {
+            startIP.add(Integer.toHexString(Integer.parseInt(parts[x], 16) & Integer.parseInt(floors[x], 2)));
+            endIP.add(Integer.toHexString(Integer.parseInt(parts[x], 16) | Integer.parseInt(ceilings[x], 2)));
         }
 
-        hexStartAddress = hexStartAddress.replaceAll("(.{4})", "$1:");
-        hexStartAddress = hexStartAddress.substring(0, hexStartAddress.length() - 1);
-        hexEndAddress = hexEndAddress.replaceAll("(.{4})", "$1:");
-        hexEndAddress = hexEndAddress.substring(0, hexEndAddress.length() - 1);
+        String hexStartAddress = ExpandIPv6(StringUtils.join(startIP, ":"));
+        String hexEndAddress = ExpandIPv6(StringUtils.join(endIP, ":"));
 
         return new String[]{hexStartAddress, hexEndAddress};
     }