PriorityQueueSerializer.java

/*
Copyright 2012 Twitter, 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.twitter.chill.java;

import com.twitter.chill.IKryoRegistrar;
import com.twitter.chill.SingleRegistrar;

import com.esotericsoftware.kryo.Kryo;
import com.esotericsoftware.kryo.Serializer;
import com.esotericsoftware.kryo.io.Input;
import com.esotericsoftware.kryo.io.Output;

import java.lang.reflect.Field;
import java.util.PriorityQueue;
import java.util.Comparator;

class PriorityQueueSerializer extends Serializer<PriorityQueue<?>> {
  private Field compField;

  static public IKryoRegistrar registrar() {
      return new SingleRegistrar(PriorityQueue.class, new PriorityQueueSerializer());
  }

  public PriorityQueueSerializer() {
    try {
      compField = PriorityQueue.class.getDeclaredField("comparator");
      compField.setAccessible(true);
    }
    catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  public Comparator<?> getComparator(PriorityQueue<?> q) {
    try {
      return (Comparator<?>)compField.get(q);
    }
    catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  public void write(Kryo k, Output o, PriorityQueue<?> q) {
    k.writeClassAndObject(o, getComparator(q));
    o.writeInt(q.size(), true);
    for(Object a : q) {
      k.writeClassAndObject(o, a);
      o.flush();
    }
  }
  public PriorityQueue<?> read(Kryo k, Input i, Class<PriorityQueue<?>> c) {
    Comparator<Object> comp = (Comparator<Object>)k.readClassAndObject(i);
    int sz = i.readInt(true);
    // can't create with size 0:
    PriorityQueue<Object> result;
    if (sz == 0) {
      result = new PriorityQueue<Object>(1, comp);
    }
    else {
      result = new PriorityQueue<Object>(sz, comp);
    }
    int idx = 0;
    while(idx < sz) {
      result.add(k.readClassAndObject(i));
      idx += 1;
    }
    return result;
  }
}