Add DomainsUtils class to encode/decode domain names.

Both encode and deocde methods support message compression which is
described in RFC1035 section 4.1.4. We can leverage both methods in
a follow-up CL to parse DHCPv4 option 119 and DNSSL RA option.

This cl also adds maxLabelCount argument for DnsRecordParser#parseName
to prevent the potential recursion from overflowing the stack.

Bug: 189865016
Test: atest NetworkStaticLibTests
Change-Id: I90101ecda64bfecb0233e80ea93c91c204fbf176
diff --git a/staticlibs/device/com/android/net/module/util/DomainUtils.java b/staticlibs/device/com/android/net/module/util/DomainUtils.java
index 80e0b64..b327fd0 100644
--- a/staticlibs/device/com/android/net/module/util/DomainUtils.java
+++ b/staticlibs/device/com/android/net/module/util/DomainUtils.java
@@ -123,7 +123,7 @@
      * @return domain name(s) string array with space separated, or empty string if decode fails.
      */
     @NonNull
-    public static String[] decode(@NonNull final ByteBuffer buffer, boolean compression) {
+    public static ArrayList<String> decode(@NonNull final ByteBuffer buffer, boolean compression) {
         final ArrayList<String> domainList = new ArrayList<>();
         while (buffer.remaining() > 0) {
             try {
@@ -138,6 +138,6 @@
                 break;
             }
         }
-        return domainList.toArray(new String[0]);
+        return domainList;
     }
 }
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/DomainUtilsTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/DomainUtilsTest.java
index 606ed5f..5eaf2ad 100644
--- a/staticlibs/tests/unit/src/com/android/net/module/util/DomainUtilsTest.java
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/DomainUtilsTest.java
@@ -30,6 +30,9 @@
 import org.junit.runner.RunWith;
 
 import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.ArrayList;
+import java.util.List;
 
 @RunWith(AndroidJUnit4.class)
 @SmallTest
@@ -168,39 +171,40 @@
 
     @Test
     public void testDecodeDomainNames() {
+        ArrayList<String> suffixStringList;
         String suffixes = "06676F6F676C6503636F6D00" // google.com
                 + "076578616D706C6503636F6D00"       // example.com
                 + "06676F6F676C6500";                // google
-        String[] expected = new String[] {"google.com", "example.com"};
+        List<String> expected = Arrays.asList("google.com", "example.com");
         ByteBuffer buffer = ByteBuffer.wrap(HexEncoding.decode(suffixes));
-        String[] suffixString = DomainUtils.decode(buffer, false /* compression */);
-        assertArrayEquals(expected, suffixString);
+        suffixStringList = DomainUtils.decode(buffer, false /* compression */);
+        assertEquals(expected, suffixStringList);
 
         // include suffix with invalid length: 64
         suffixes = "06676F6F676C6503636F6D00"        // google.com
                 + "406578616D706C6503636F6D00"       // example.com(length=64)
                 + "06676F6F676C6500";                // google
-        expected = new String[] {"google.com"};
+        expected = Arrays.asList("google.com");
         buffer = ByteBuffer.wrap(HexEncoding.decode(suffixes));
-        suffixString = DomainUtils.decode(buffer, false /* compression */);
-        assertArrayEquals(expected, suffixString);
+        suffixStringList = DomainUtils.decode(buffer, false /* compression */);
+        assertEquals(expected, suffixStringList);
 
         // include suffix with invalid length: 0
         suffixes = "06676F6F676C6503636F6D00"         // google.com
                 + "076578616D706C6503636F6D00"        // example.com
                 + "00676F6F676C6500";                 // google(length=0)
-        expected = new String[] {"google.com", "example.com"};
+        expected = Arrays.asList("google.com", "example.com");
         buffer = ByteBuffer.wrap(HexEncoding.decode(suffixes));
-        suffixString = DomainUtils.decode(buffer, false /* compression */);
-        assertArrayEquals(expected, suffixString);
+        suffixStringList = DomainUtils.decode(buffer, false /* compression */);
+        assertEquals(expected, suffixStringList);
 
         suffixes =
                 "076578616D706C6504636F727006676F6F676C6503636F6D00"  // example.corp.google.com
                 + "C008"                                              // corp.google.com
                 + "C00D";                                             // google.com
-        expected = new String[] {"example.corp.google.com", "corp.google.com", "google.com"};
+        expected = Arrays.asList("example.corp.google.com", "corp.google.com", "google.com");
         buffer = ByteBuffer.wrap(HexEncoding.decode(suffixes));
-        suffixString = DomainUtils.decode(buffer, true /* compression */);
-        assertArrayEquals(expected, suffixString);
+        suffixStringList = DomainUtils.decode(buffer, true /* compression */);
+        assertEquals(expected, suffixStringList);
     }
 }