Import code from internal repository to git

java/com/google/domain/registry/util/DomainNameUtils.java

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+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// 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 com.google.domain.registry.util;
+
+import com.google.common.base.Ascii;
+import com.google.common.net.InternetDomainName;
+
+/** Utility methods related to domain names. */
+public final class DomainNameUtils {
+
+  /** Prefix for unicode domain name parts. */
+  public static final String ACE_PREFIX = "xn--";
+  public static final String ACE_PREFIX_REGEX = "^xn--";
+
+  /** Checks whether "name" is a strict subdomain of "potentialParent". */
+  public static boolean isUnder(InternetDomainName name, InternetDomainName potentialParent) {
+    int numNameParts = name.parts().size();
+    int numParentParts = potentialParent.parts().size();
+    return numNameParts > numParentParts
+        && name.parts().subList(numNameParts - numParentParts, numNameParts)
+            .equals(potentialParent.parts());
+  }
+
+  /** Canonicalizes a domain name by lowercasing and converting unicode to punycode. */
+  public static String canonicalizeDomainName(String label) {
+    return Idn.toASCII(Ascii.toLowerCase(label));
+  }
+
+  private DomainNameUtils() {}
+}