Save bloom filters for premium list entries

This is the first step in the migration to remove the need to load all of
the premium list entries every time the cache expires (which causes slow-
downs). Once this is deployed, we can re-save all premium lists, creating
the bloom filters, and then the next step will be to read from them to
more efficiently determine if a label might be premium.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=147525017

java/google/registry/model/translators/BloomFilterOfStringTranslatorFactory.java

@@ -0,0 +1,90 @@
+// Copyright 2017 The Nomulus Authors. 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 google.registry.model.translators;
+
+import static com.google.common.hash.Funnels.unencodedCharsFunnel;
+import static com.googlecode.objectify.repackaged.gentyref.GenericTypeReflector.erase;
+import static com.googlecode.objectify.repackaged.gentyref.GenericTypeReflector.getTypeParameter;
+
+import com.google.appengine.api.datastore.Blob;
+import com.google.common.hash.BloomFilter;
+import com.google.common.hash.Funnel;
+import com.google.common.reflect.TypeToken;
+import com.googlecode.objectify.impl.Path;
+import com.googlecode.objectify.impl.Property;
+import com.googlecode.objectify.impl.translate.CreateContext;
+import com.googlecode.objectify.impl.translate.LoadContext;
+import com.googlecode.objectify.impl.translate.SaveContext;
+import com.googlecode.objectify.impl.translate.Translator;
+import com.googlecode.objectify.impl.translate.TranslatorFactory;
+import com.googlecode.objectify.impl.translate.ValueTranslator;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.lang.reflect.Type;
+import javax.annotation.Nullable;
+
+/** Stores CharSequence {@link BloomFilter}s as blobs. */
+public class BloomFilterOfStringTranslatorFactory
+    implements TranslatorFactory<BloomFilter<String>> {
+
+  @Override
+  public Translator<BloomFilter<String>> create(
+      Path path, Property property, Type type, CreateContext ctx) {
+    if (!BloomFilter.class.equals(erase(type))) {
+      return null;  // Skip me and try to find another matching translator
+    }
+    Type fieldBloomFilterType = getTypeParameter(type, BloomFilter.class.getTypeParameters()[0]);
+    if (fieldBloomFilterType == null) {
+      return null;  // No type information is available
+    }
+    if (!TypeToken.of(String.class).getType().equals(fieldBloomFilterType)) {
+      return null;  // We can only handle BloomFilters of CharSequences
+    }
+
+    return new ValueTranslator<BloomFilter<String>, Blob>(path, Blob.class) {
+
+      @Override
+      @Nullable
+      protected BloomFilter<String> loadValue(Blob value, LoadContext ctx) {
+        if (value == null) {
+          return null;
+        }
+        try {
+          @SuppressWarnings("unchecked")
+          Funnel<String> castedFunnel = (Funnel<String>) (Funnel<?>) unencodedCharsFunnel();
+          return BloomFilter.readFrom(new ByteArrayInputStream(value.getBytes()), castedFunnel);
+        } catch (IOException e) {
+          throw new IllegalStateException("Error loading bloom filter data", e);
+        }
+      }
+
+      @Override
+      @Nullable
+      protected Blob saveValue(BloomFilter<String> value, SaveContext ctx) {
+        if (value == null) {
+          return null;
+        }
+        ByteArrayOutputStream bos = new ByteArrayOutputStream();
+        try {
+          value.writeTo(bos);
+        } catch (IOException e) {
+          throw new IllegalStateException("Error saving bloom filter data", e);
+        }
+        return new Blob(bos.toByteArray());
+      }
+    };
+  }
+}