Added IP.isLoopback

src/dorkbox/netUtil/IPv4.kt

@@ -90,6 +90,7 @@ object IPv4 {
     private val private10 = toInt("10.0.0.0")
     private val private172 = toInt("172.16.0.0")
     private val private192 = toInt("192.168.0.0")
+    private val loopback172 = toInt("127.0.0.0")
 
     /**
      * Determines if this IP address is a private address or not.
@@ -116,6 +117,22 @@ object IPv4 {
         return isInRange(ipAsInt, private192, 16) || isInRange(ipAsInt, private172, 12) || isInRange(ipAsInt, private10, 8)
     }
 
+    /**
+     * A loopback address is defined as
+     *  127.0.0.0/8
+     */
+    fun isLoopback(ipAsString: String): Boolean {
+        return isInRange(toInt(ipAsString), loopback172, 8)
+    }
+
+    /**
+     * A loopback address is defined as
+     *  127.0.0.0/8
+     */
+    fun isLoopback(ipAsInt: Int): Boolean {
+        return isInRange(ipAsInt, loopback172, 8)
+    }
+
     /**
      * Determine whether a given string is a valid CIDR IP address. Accepts only 1.2.3.4/24
      *

src/dorkbox/netUtil/IPv6.kt

@@ -250,8 +250,6 @@ object IPv6 {
         } catch (e: UnknownHostException) {
             throw RuntimeException(e) // Should never happen
         }
-
-//        return NetUtil.getByName(ip, ipv4Mapped)
     }
 
     /**
@@ -688,4 +686,36 @@ object IPv6 {
     private fun inRangeEndExclusive(value: Int, start: Int, end: Int): Boolean {
         return value >= start && value < end
     }
+
+
+    /**
+     * IPv6 address reserved for loopback use is 0000:0000:0000:0000:0000:0000:0000:0001/128.
+     *
+     * This loopback address is so lengthy and can be further simplified as ::1/128, or just ::1
+     *
+     * /128 means EXACTLY this address
+     */
+    fun isLoopback(ipAsString: String): Boolean {
+        var oneCount = 0
+        // can only be with one "1", and nothing else
+        ipAsString.forEach { char ->
+            when (char) {
+                ':' -> {
+                    // this is always ok
+                }
+                '1' -> {
+                    oneCount++
+                    if (oneCount > 1) {
+                        return false
+                    }
+                }
+                else -> {
+                    // not OK
+                    return false
+                }
+            }
+        }
+
+        return oneCount == 1
+    }
 }