From b95d9dff5c02b234efdd1b93403b3353c12ee6b2 Mon Sep 17 00:00:00 2001
From: RenFei <i@renfei.net>
Date: Thu, 16 Nov 2023 09:38:22 +0800
Subject: [PATCH] Fixed wrong value returned by CIDRToIPv6 function

see: https://github.com/ip2location/ip2location-java/commit/6ff27d6972c3a7a8a9cbff08472ec377959c5157
---
 README.md                                     |  2 +-
 README_zh.md                                  |  2 +-
 pom.xml                                       | 10 +++-
 .../java/net/renfei/ip2location/IPTools.java  | 46 ++++++++-----------
 4 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/README.md b/README.md
index 61bbbf9..57429dc 100644
--- a/README.md
+++ b/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>
 ```
 
diff --git a/README_zh.md b/README_zh.md
index 67b1ec6..ca489ee 100644
--- a/README_zh.md
+++ b/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>
 ```
 
diff --git a/pom.xml b/pom.xml
index 284b30e..d4ef1ba 100644
--- a/pom.xml
+++ b/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>
diff --git a/src/main/java/net/renfei/ip2location/IPTools.java b/src/main/java/net/renfei/ip2location/IPTools.java
index 953e46c..7481c03 100644
--- a/src/main/java/net/renfei/ip2location/IPTools.java
+++ b/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};
     }