001/*
002 * Copyright (C) 2011 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.hash;
016
017import com.google.common.annotations.Beta;
018import com.google.errorprone.annotations.DoNotMock;
019import java.io.Serializable;
020import org.checkerframework.checker.nullness.qual.Nullable;
021
022/**
023 * An object which can send data from an object of type {@code T} into a {@code PrimitiveSink}.
024 * Implementations for common types can be found in {@link Funnels}.
025 *
026 * <p>Note that serialization of {@linkplain BloomFilter bloom filters} requires the proper
027 * serialization of funnels. When possible, it is recommended that funnels be implemented as a
028 * single-element enum to maintain serialization guarantees. See Effective Java (2nd Edition), Item
029 * 3: "Enforce the singleton property with a private constructor or an enum type". For example:
030 *
031 * <pre>{@code
032 * public enum PersonFunnel implements Funnel<Person> {
033 *   INSTANCE;
034 *   public void funnel(Person person, PrimitiveSink into) {
035 *     into.putUnencodedChars(person.getFirstName())
036 *         .putUnencodedChars(person.getLastName())
037 *         .putInt(person.getAge());
038 *   }
039 * }
040 * }</pre>
041 *
042 * @author Dimitris Andreou
043 * @since 11.0
044 */
045@Beta
046@DoNotMock("Implement with a lambda")
047@ElementTypesAreNonnullByDefault
048public interface Funnel<T extends @Nullable Object> extends Serializable {
049
050  /**
051   * Sends a stream of data from the {@code from} object into the sink {@code into}. There is no
052   * requirement that this data be complete enough to fully reconstitute the object later.
053   *
054   * @since 12.0 (in Guava 11.0, {@code PrimitiveSink} was named {@code Sink})
055   */
056  void funnel(@ParametricNullness T from, PrimitiveSink into);
057}