Completed the IPv6 implementation for IpPrefix, and added

a new set of IpPrefix unit tests.

Also, fix few nits in IpAddress and IpAddressTest

@@ -30,7 +30,6 @@ import static com.google.common.base.Preconditions.checkState;
 
 /**
  * A class representing an IP address.
- * TODO: Add support for IPv6 as well.
  */
 public final class IpAddress implements Comparable<IpAddress> {
     // IP Versions

@@ -17,8 +17,6 @@ package org.onlab.packet;
 
 import java.util.Objects;
 
-// TODO: Add support for IPv6 as well.
-
 /**
  * A class representing an IP prefix. A prefix consists of an IP address and
  * a subnet mask.
@@ -40,26 +38,39 @@ public final class IpPrefix {
      *
      * @param address the IP address
      * @param prefixLength the prefix length
+     * @throws IllegalArgumentException if the prefix length value is invalid
      */
     private IpPrefix(IpAddress address, int prefixLength) {
-        checkPrefixLength(prefixLength);
+        checkPrefixLength(address.version(), prefixLength);
         this.address = IpAddress.makeMaskedAddress(address, prefixLength);
         this.prefixLength = (short) prefixLength;
     }
 
     /**
-     * Checks whether the prefix length is valid.
+     * Returns the IP version of the prefix.
      *
-     * @param prefixLength the prefix length value to check
-     * @throws IllegalArgumentException if the prefix length value is invalid
+     * @return the IP version of the prefix
      */
-    private static void checkPrefixLength(int prefixLength) {
-        if ((prefixLength < 0) || (prefixLength > MAX_INET_MASK_LENGTH)) {
-            String msg = "Invalid prefix length " + prefixLength + ". " +
-                "The value must be in the interval [0, " +
-                MAX_INET_MASK_LENGTH + "]";
-            throw new IllegalArgumentException(msg);
-        }
+    public IpAddress.Version version() {
+        return address.version();
+    }
+
+    /**
+     * Returns the IP address value of the prefix.
+     *
+     * @return the IP address value of the prefix
+     */
+    public IpAddress address() {
+        return address;
+    }
+
+    /**
+     * Returns the IP address prefix length.
+     *
+     * @return the IP address prefix length
+     */
+    public int prefixLength() {
+        return prefixLength;
     }
 
     /**
@@ -68,6 +79,7 @@ public final class IpPrefix {
      * @param address an integer representing the IPv4 address
      * @param prefixLength the prefix length
      * @return an IP prefix
+     * @throws IllegalArgumentException if the prefix length value is invalid
      */
     public static IpPrefix valueOf(int address, int prefixLength) {
         return new IpPrefix(IpAddress.valueOf(address), prefixLength);
@@ -80,11 +92,11 @@ public final class IpPrefix {
      * @param address the IP address value stored in network byte order
      * @param prefixLength the prefix length
      * @return an IP prefix
+     * @throws IllegalArgumentException if the prefix length value is invalid
      */
     public static IpPrefix valueOf(IpAddress.Version version, byte[] address,
                                    int prefixLength) {
-        return new IpPrefix(IpAddress.valueOf(version, address),
-                            prefixLength);
+        return new IpPrefix(IpAddress.valueOf(version, address), prefixLength);
     }
 
     /**
@@ -93,6 +105,7 @@ public final class IpPrefix {
      * @param address the IP address
      * @param prefixLength the prefix length
      * @return an IP prefix
+     * @throws IllegalArgumentException if the prefix length value is invalid
      */
     public static IpPrefix valueOf(IpAddress address, int prefixLength) {
         return new IpPrefix(address, prefixLength);
@@ -104,6 +117,7 @@ public final class IpPrefix {
      *
      * @param address an IP prefix in string form, e.g. "10.1.0.0/16"
      * @return an IP prefix
+     * @throws IllegalArgumentException if the arguments are invalid
      */
     public static IpPrefix valueOf(String address) {
         final String[] parts = address.split("/");
@@ -119,33 +133,6 @@ public final class IpPrefix {
     }
 
     /**
-     * Returns the IP version of the prefix.
-     *
-     * @return the IP version of the prefix
-     */
-    public IpAddress.Version version() {
-        return address.version();
-    }
-
-    /**
-     * Returns the IP address value of the prefix.
-     *
-     * @return the IP address value of the prefix
-     */
-    public IpAddress address() {
-        return address;
-    }
-
-    /**
-     * Returns the IP address prefix length.
-     *
-     * @return the IP address prefix length
-     */
-    public int prefixLength() {
-        return prefixLength;
-    }
-
-    /**
      * Determines whether a given IP prefix is contained within this prefix.
      *
      * @param other the IP prefix to test
@@ -217,4 +204,35 @@ public final class IpPrefix {
         builder.append(String.format("%d", prefixLength));
         return builder.toString();
     }
+
+    /**
+     * Checks whether the prefix length is valid.
+     *
+     * @param version the IP address version
+     * @param prefixLength the prefix length value to check
+     * @throws IllegalArgumentException if the prefix length value is invalid
+     */
+    private static void checkPrefixLength(IpAddress.Version version,
+                                          int prefixLength) {
+        int maxPrefixLen = 0;
+
+        switch (version) {
+        case INET:
+            maxPrefixLen = MAX_INET_MASK_LENGTH;
+            break;
+        case INET6:
+            maxPrefixLen = MAX_INET6_MASK_LENGTH;
+            break;
+        default:
+            String msg = "Invalid IP version " + version;
+            throw new IllegalArgumentException(msg);
+        }
+
+        if ((prefixLength < 0) || (prefixLength > maxPrefixLen)) {
+            String msg = "Invalid prefix length " + prefixLength + ". " +
+                "The value must be in the interval [0, " +
+                maxPrefixLen + "]";
+            throw new IllegalArgumentException(msg);
+        }
+    }
 }

@@ -135,7 +135,7 @@ public class IpAddressTest {
      * Tests returning an IPv4 address asn an integer.
      */
     @Test
-    public void testToint() {
+    public void testToInt() {
         IpAddress ipAddress;
 
         ipAddress = IpAddress.valueOf("1.2.3.4");
@@ -149,10 +149,10 @@ public class IpAddressTest {
     }
 
     /**
-     * Tests valueOf() converter for an integer value.
+     * Tests valueOf() converter for IPv4 integer value.
      */
     @Test
-    public void testValueOfForInteger() {
+    public void testValueOfForIntegerIPv4() {
         IpAddress ipAddress;
 
         ipAddress = IpAddress.valueOf(0x01020304);