fix IP range to CIDR parser

Author: Athlon1600

src/global.php

@@ -2,6 +2,18 @@
 
 use ProxyNova\RangeOptimizer\CIDR;
 
+if (!function_exists('cidr_mask_length')) {
+
+    // Formula: # of IP addresses = 2^(32 - CIDR suffix)
+    function cidr_mask_length(int $start, int $end): int
+    {
+        $prefix = 32 - log($end - $start + 1, 2);
+        $prefix = (int)ceil($prefix);
+
+        return min(32, $prefix);
+    }
+}
+
 /**
  * can return multiple ranges
  *
@@ -12,22 +24,26 @@
 function range_to_cidr(int $start, int $end): array
 {
     $ranges = [];
-    $maxSize = 32;
 
     // until no ranges left
     while ($start <= $end) {
 
-        $prefix = long2ip($start);
-        $diff = $end - $start;
+        $address = long2ip($start);
+
+        // from: https://github.com/allaboutjst/airbnb/blob/master/src/main/java/ip_range_to_cidr/IPRangetoCIDR.java#L41
+        // Find the location of the first 1 bit
+        $locOfFirstOne = $start & (-$start);
+
+        // Calculate the corresponding mask
+        $curMask = 32 - (int)(log($locOfFirstOne) / log(2));
 
-        $bits = 32 - log($diff + 1, 2);
+        $maxLen = cidr_mask_length($start, $end);
+        $prefixLength = max($curMask, $maxLen);
 
-        // larger length => smaller range
-        $bits = min($maxSize, ceil($bits));
-        $ranges[] = new CIDR($prefix . '/' . $bits);
+        $ranges[] = new CIDR($address . '/' . $prefixLength);
 
         // how many IPs was that?
-        $ipCount = pow(2, 32 - $bits);
+        $ipCount = pow(2, 32 - $prefixLength);
 
         $start += $ipCount;
     }

tests/CIDRTest.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace ProxyNova\RangeOptimizer\Tests;
+
+use PHPUnit\Framework\TestCase;
+use ProxyNova\RangeOptimizer\CIDR;
+
+class CIDRTest extends TestCase
+{
+    public function test_parse()
+    {
+        // CIDR => [expected network, expected broadcast]
+        $data = [
+            "172.233.173.111/8" => ["172.0.0.0", "172.255.255.255"],
+            "74.207.237.201/14" => ["74.204.0.0", "74.207.255.255"],
+            "45.33.60.45/7" => ["44.0.0.0", "45.255.255.255"]
+        ];
+
+        foreach ($data as $input => $outputs) {
+            $temp = new CIDR($input);
+
+            $this->assertEquals($outputs[0], $temp->getFirstAddress());
+            $this->assertEquals($outputs[1], $temp->getLastAddress());
+        }
+    }
+
+    public function test_range_to_cidr()
+    {
+        // start IP, end IP, CIDRs
+        $ranges = [
+            ["13.49.126.128", "13.49.126.191", ["13.49.126.128/26"]],
+            ["18.139.204.176", "18.139.204.223", ["18.139.204.176/28", "18.139.204.192/27"]],
+            ["3.25.37.128", "3.25.40.255", ["3.25.37.128/25", "3.25.38.0/23", "3.25.40.0/24"]],
+            ["35.80.36.208", "35.80.36.239", ["35.80.36.208/28", "35.80.36.224/28"]]
+        ];
+
+        foreach ($ranges as $range) {
+
+            $cidrArray = range_to_cidr(ip2long($range[0]), ip2long($range[1]));
+            $expected = $range[2];
+
+            $this->assertEquals(count($expected), count($cidrArray));
+
+            foreach ($expected as $index => $value) {
+                $str = strval($cidrArray[$index]);
+                $this->assertEquals($value, $str);
+            }
+        }
+    }
+}