caliper/src/main/java/com/google/caliper/model/Host.java

/*
 * Copyright (C) 2012 Google Inc.
 *
 * 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.caliper.model;

import static com.google.caliper.model.PersistentHashing.getPersistentHashFunction;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.MoreObjects;
import com.google.common.collect.ImmutableSortedMap;
import com.google.common.collect.Maps;
import com.google.common.hash.Funnel;
import com.google.common.hash.HashFunction;
import com.google.common.hash.PrimitiveSink;

import java.util.Map;
import java.util.SortedMap;
import java.util.logging.Logger;

/**
 * The performance-informing properties of the host on which a benchmark is run.
 *
 * @author gak@google.com (Gregory Kick)
 */
public final class Host {
  static final Host DEFAULT = new Host();
  private static final Logger logger = Logger.getLogger(Host.class.getName());

  @ExcludeFromJson private int id;
  private SortedMap<String, String> properties;
  @ExcludeFromJson private int hash;

  private Host() {
    this.properties = Maps.newTreeMap();
  }

  private Host(Builder builder) {
    this.properties = Maps.newTreeMap(builder.properties);
    // eagerly initialize hash to allow for the test-only hash function
    initHash(builder.hashFunction);
  }

  public ImmutableSortedMap<String, String> properties() {
    return ImmutableSortedMap.copyOf(properties);
  }

  @Override public boolean equals(Object obj) {
    if (obj == this) {
      return true;
    } else if (obj instanceof Host) {
      Host that = (Host) obj;
      return this.properties.equals(that.properties);
    } else {
      return false;
    }
  }

  private void initHash(HashFunction hashFunction) {
    if (hash == 0) {
      this.hash = hashFunction.hashObject(this, HostFunnel.INSTANCE).asInt();
    }
  }

  private void initHash() {
    initHash(getPersistentHashFunction());
  }

  @Override public int hashCode() {
    initHash();
    return hash;
  }

  @Override public String toString() {
    return MoreObjects.toStringHelper(this)
        .add("properties", properties)
        .toString();
  }

  enum HostFunnel implements Funnel<Host> {
    INSTANCE;

    @Override public void funnel(Host from, PrimitiveSink into) {
      StringMapFunnel.INSTANCE.funnel(from.properties, into);
    }
  }

  public static final class Builder {
    private final SortedMap<String, String> properties = Maps.newTreeMap();
    private HashFunction hashFunction = getPersistentHashFunction();

    public Builder addProperty(String key, String value) {
      properties.put(key, value);
      return this;
    }

    public Builder addAllProperies(Map<String, String> properties) {
      this.properties.putAll(properties);
      return this;
    }

    /**
     * This only exists for tests to induce hash collisions. Only use this in test code as changing
     * the hash function will break persisted objects.
     */
    @VisibleForTesting public Builder hashFunctionForTesting(HashFunction hashFunction) {
      logger.warning("somebody is setting the hash function. this should only be used in tests");
      this.hashFunction = checkNotNull(hashFunction);
      return this;
    }

    public Host build() {
      return new Host(this);
    }
  }
}