Minor changes to LinkAddress.

1. Simplify the parceling code. Since the InetAddress inside a
   LinkAddress can never be null, we don't need to special-case
   the case where it is.
2. Add / update method documentation.
3. Write a unit test.

Change-Id: Iba0a8cecc683d55d736419965e72ee33dd66dc22

core/java/android/net/LinkAddress.java

@@ -25,7 +25,7 @@ import java.net.InterfaceAddress;
 import java.net.UnknownHostException;
 
 /**
- * Identifies an address of a network link
+ * Identifies an IP address on a network link.
  * @hide
  */
 public class LinkAddress implements Parcelable {
@@ -35,7 +35,7 @@ public class LinkAddress implements Parcelable {
     private InetAddress address;
 
     /**
-     * Network prefix length
+     * Prefix length.
      */
     private int prefixLength;
 
@@ -50,10 +50,19 @@ public class LinkAddress implements Parcelable {
         this.prefixLength = prefixLength;
     }
 
+    /**
+     * Constructs a new {@code LinkAddress} from an {@code InetAddress} and a prefix length.
+     * @param address The IP address.
+     * @param prefixLength The prefix length.
+     */
     public LinkAddress(InetAddress address, int prefixLength) {
         init(address, prefixLength);
     }
 
+    /**
+     * Constructs a new {@code LinkAddress} from an {@code InterfaceAddress}.
+     * @param interfaceAddress The interface address.
+     */
     public LinkAddress(InterfaceAddress interfaceAddress) {
         init(interfaceAddress.getAddress(),
              interfaceAddress.getNetworkPrefixLength());
@@ -86,13 +95,13 @@ public class LinkAddress implements Parcelable {
 
     @Override
     public String toString() {
-        return (address == null ? "" : (address.getHostAddress() + "/" + prefixLength));
+        return address.getHostAddress() + "/" + prefixLength;
     }
 
     /**
      * Compares this {@code LinkAddress} instance against the specified address
      * in {@code obj}. Two addresses are equal if their InetAddress and prefixLength
-     * are equal
+     * are equal.
      *
      * @param obj the object to be tested for equality.
      * @return {@code true} if both objects are equal, {@code false} otherwise.
@@ -107,30 +116,30 @@ public class LinkAddress implements Parcelable {
             this.prefixLength == linkAddress.prefixLength;
     }
 
-    @Override
+    /**
-    /*
+     * Returns a hashcode for this address.
-     * generate hashcode based on significant fields
      */
+    @Override
     public int hashCode() {
-        return ((null == address) ? 0 : address.hashCode()) + prefixLength;
+        return address.hashCode() + 11 * prefixLength;
     }
 
     /**
-     * Returns the InetAddress for this address.
+     * Returns the InetAddress of this address.
      */
     public InetAddress getAddress() {
         return address;
     }
 
     /**
-     * Get network prefix length
+     * Returns the prefix length of this address.
      */
     public int getNetworkPrefixLength() {
         return prefixLength;
     }
 
     /**
-     * Implement the Parcelable interface
+     * Implement the Parcelable interface.
      * @hide
      */
     public int describeContents() {
@@ -142,13 +151,8 @@ public class LinkAddress implements Parcelable {
      * @hide
      */
     public void writeToParcel(Parcel dest, int flags) {
-        if (address != null) {
+        dest.writeByteArray(address.getAddress());
-            dest.writeByte((byte)1);
+        dest.writeInt(prefixLength);
-            dest.writeByteArray(address.getAddress());
-            dest.writeInt(prefixLength);
-        } else {
-            dest.writeByte((byte)0);
-        }
     }
 
     /**
@@ -159,13 +163,14 @@ public class LinkAddress implements Parcelable {
         new Creator<LinkAddress>() {
             public LinkAddress createFromParcel(Parcel in) {
                 InetAddress address = null;
-                int prefixLength = 0;
+                try {
-                if (in.readByte() == 1) {
+                    address = InetAddress.getByAddress(in.createByteArray());
-                    try {
+                } catch (UnknownHostException e) {
-                        address = InetAddress.getByAddress(in.createByteArray());
+                    // Nothing we can do here. When we call the constructor, we'll throw an
-                        prefixLength = in.readInt();
+                    // IllegalArgumentException, because a LinkAddress can't have a null
-                    } catch (UnknownHostException e) { }
+                    // InetAddress.
                 }
+                int prefixLength = in.readInt();
                 return new LinkAddress(address, prefixLength);
             }
 

core/tests/coretests/src/android/net/LinkAddressTest.java

@@ -0,0 +1,213 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.net;
+
+import java.net.Inet4Address;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.net.InterfaceAddress;
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+import android.net.LinkAddress;
+import android.os.Parcel;
+import android.test.AndroidTestCase;
+import android.test.suitebuilder.annotation.SmallTest;
+
+/**
+ * Tests for {@link LinkAddress}.
+ */
+public class LinkAddressTest extends AndroidTestCase {
+
+    private static final String V4 = "192.0.2.1";
+    private static final String V6 = "2001:db8::1";
+    private static final InetAddress V4_ADDRESS = NetworkUtils.numericToInetAddress(V4);
+    private static final InetAddress V6_ADDRESS = NetworkUtils.numericToInetAddress(V6);
+
+    public void testConstructors() throws SocketException {
+        LinkAddress address;
+
+        // Valid addresses work as expected.
+        address = new LinkAddress(V4_ADDRESS, 25);
+        assertEquals(V4_ADDRESS, address.getAddress());
+        assertEquals(25, address.getNetworkPrefixLength());
+
+        address = new LinkAddress(V6_ADDRESS, 127);
+        assertEquals(V6_ADDRESS, address.getAddress());
+        assertEquals(127, address.getNetworkPrefixLength());
+
+        address = new LinkAddress(V6 + "/64");
+        assertEquals(V6_ADDRESS, address.getAddress());
+        assertEquals(64, address.getNetworkPrefixLength());
+
+        address = new LinkAddress(V4 + "/23");
+        assertEquals(V4_ADDRESS, address.getAddress());
+        assertEquals(23, address.getNetworkPrefixLength());
+
+        // InterfaceAddress doesn't have a constructor. Fetch some from an interface.
+        List<InterfaceAddress> addrs = NetworkInterface.getByName("lo").getInterfaceAddresses();
+
+        // We expect to find 127.0.0.1/8 and ::1/128, in any order.
+        LinkAddress ipv4Loopback, ipv6Loopback;
+        assertEquals(2, addrs.size());
+        if (addrs.get(0).getAddress() instanceof Inet4Address) {
+            ipv4Loopback = new LinkAddress(addrs.get(0));
+            ipv6Loopback = new LinkAddress(addrs.get(1));
+        } else {
+            ipv4Loopback = new LinkAddress(addrs.get(1));
+            ipv6Loopback = new LinkAddress(addrs.get(0));
+        }
+
+        assertEquals(NetworkUtils.numericToInetAddress("127.0.0.1"), ipv4Loopback.getAddress());
+        assertEquals(8, ipv4Loopback.getNetworkPrefixLength());
+
+        assertEquals(NetworkUtils.numericToInetAddress("::1"), ipv6Loopback.getAddress());
+        assertEquals(128, ipv6Loopback.getNetworkPrefixLength());
+
+        // Null addresses are rejected.
+        try {
+            address = new LinkAddress(null, 24);
+            fail("Null InetAddress should cause IllegalArgumentException");
+        } catch(IllegalArgumentException expected) {}
+
+        try {
+            address = new LinkAddress((String) null);
+            fail("Null string should cause IllegalArgumentException");
+        } catch(IllegalArgumentException expected) {}
+
+        try {
+            address = new LinkAddress((InterfaceAddress) null);
+            fail("Null string should cause NullPointerException");
+        } catch(NullPointerException expected) {}
+
+        // Invalid prefix lengths are rejected.
+        try {
+            address = new LinkAddress(V4 + "/-1");
+            fail("Negative IPv4 prefix length should cause IllegalArgumentException");
+        } catch(IllegalArgumentException expected) {}
+
+        try {
+            address = new LinkAddress(V6 + "/-1");
+            fail("Negative IPv6 prefix length should cause IllegalArgumentException");
+        } catch(IllegalArgumentException expected) {}
+
+        try {
+            address = new LinkAddress(V4 + "/33");
+            fail("/35 IPv4 prefix length should cause IllegalArgumentException");
+        } catch(IllegalArgumentException expected) {}
+
+        try {
+            address = new LinkAddress(V6 + "/129");
+            fail("/129 IPv6 prefix length should cause IllegalArgumentException");
+        } catch(IllegalArgumentException expected) {}
+    }
+
+    private void assertLinkAddressesEqual(LinkAddress l1, LinkAddress l2) {
+        assertTrue(l1 + " unexpectedly not equal to " + l2, l1.equals(l2));
+        assertTrue(l2 + " unexpectedly not equal to " + l1, l2.equals(l1));
+        assertEquals(l1.hashCode(), l2.hashCode());
+    }
+
+    private void assertLinkAddressesNotEqual(LinkAddress l1, LinkAddress l2) {
+        assertFalse(l1 + " unexpectedly equal to " + l2, l1.equals(l2));
+        assertFalse(l2 + " unexpectedly equal to " + l1, l2.equals(l1));
+    }
+
+    public void testEquals() {
+        LinkAddress l1, l2;
+
+        l1 = new LinkAddress("2001:db8::1/64");
+        l2 = new LinkAddress("2001:db8::1/64");
+        assertLinkAddressesEqual(l1, l2);
+
+        l2 = new LinkAddress("2001:db8::1/65");
+        assertLinkAddressesNotEqual(l1, l2);
+        l2 = new LinkAddress("2001:db8::2/64");
+        assertLinkAddressesNotEqual(l1, l2);
+
+        l1 = new LinkAddress("192.0.2.1/24");
+        l2 = new LinkAddress("192.0.2.1/24");
+        assertLinkAddressesEqual(l1, l2);
+
+        l2 = new LinkAddress("192.0.2.1/23");
+        assertLinkAddressesNotEqual(l1, l2);
+        l2 = new LinkAddress("192.0.2.2/24");
+        assertLinkAddressesNotEqual(l1, l2);
+
+        // Addresses with the same start or end bytes aren't equal between families.
+        l1 = new LinkAddress("255.255.255.255/24");
+        l2 = new LinkAddress("ffff:ffff::/24");
+        assertLinkAddressesNotEqual(l1, l2);
+        l2 = new LinkAddress("::ffff:ffff/24");
+        assertLinkAddressesNotEqual(l1, l2);
+
+        // Because we use InetAddress, an IPv4 address is equal to its IPv4-mapped address.
+        // TODO: Investigate fixing this.
+        String addressString = V4 + "/24";
+        l1 = new LinkAddress(addressString);
+        l2 = new LinkAddress("::ffff:" + addressString);
+        assertLinkAddressesEqual(l1, l2);
+    }
+
+    public void testHashCode() {
+        LinkAddress l;
+
+        l = new LinkAddress(V4_ADDRESS, 23);
+        assertEquals(-982787, l.hashCode());
+
+        l = new LinkAddress(V4_ADDRESS, 27);
+        assertEquals(-982743, l.hashCode());
+
+        l = new LinkAddress(V6_ADDRESS, 64);
+        assertEquals(1076522926, l.hashCode());
+
+        l = new LinkAddress(V6_ADDRESS, 128);
+        assertEquals(1076523630, l.hashCode());
+    }
+
+    private LinkAddress passThroughParcel(LinkAddress l) {
+        Parcel p = Parcel.obtain();
+        LinkAddress l2 = null;
+        try {
+            l.writeToParcel(p, 0);
+            p.setDataPosition(0);
+            l2 = LinkAddress.CREATOR.createFromParcel(p);
+        } finally {
+            p.recycle();
+        }
+        assertNotNull(l2);
+        return l2;
+    }
+
+    private void assertParcelingIsLossless(LinkAddress l) {
+      LinkAddress l2 = passThroughParcel(l);
+      assertEquals(l, l2);
+    }
+
+    public void testParceling() {
+        LinkAddress l;
+
+        l = new LinkAddress(V6_ADDRESS, 64);
+        assertParcelingIsLossless(l);
+
+        l = new LinkAddress(V4 + "/28");
+        assertParcelingIsLossless(l);
+    }
+}