ConsensusMessage.java

/**
Copyright (c) 2007-2013 Alysson Bessani, Eduardo Alchieri, Paulo Sousa, and the authors indicated in the @author tags

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 bftsmart.consensus.messages;

import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import bftsmart.communication.SystemMessage;



/**
 * This class represents a message used in a epoch of a consensus instance.
 */
public class ConsensusMessage extends SystemMessage {

    private int number; //consensus ID for this message
    private int epoch; // Epoch to which this message belongs to
    private int paxosType; // Message type
    private byte[] value = null; // Value used when message type is PROPOSE
    private Object proof; // Proof used when message type is COLLECT
                              // Can be either a MAC vector or a RSA signature

    /**
     * Creates a consensus message. Not used. TODO: How about making it private?
     */
    public ConsensusMessage(){}

    /**
     * Creates a consensus message. Used by the message factory to create a COLLECT or PROPOSE message
     * TODO: How about removing the modifier, to make it visible just within the package?
     * @param paxosType This should be MessageFactory.COLLECT or MessageFactory.PROPOSE
     * @param id Consensus's ID
     * @param epoch Epoch timestamp
     * @param from This should be this process ID
     * @param value This should be null if its a COLLECT message, or the proposed value if it is a PROPOSE message
     */
    public ConsensusMessage(int paxosType, int id,int epoch,int from, byte[] value){

        super(from);

        this.paxosType = paxosType;
        this.number = id;
        this.epoch = epoch;
        this.value = value;
        //this.macVector = proof;

    }


    /**
     * Creates a consensus message. Used by the message factory to create a FREEZE message
     * TODO: How about removing the modifier, to make it visible just within the package?
     * @param type This should be MessageFactory.FREEZE
     * @param id Consensus's consensus ID
     * @param epoch Epoch timestamp
     * @param from This should be this process ID
     */
    public ConsensusMessage(int type, int id,int epoch, int from) {

        this(type, id, epoch, from, null);

    }

    // Implemented method of the Externalizable interface
    @Override
    public void writeExternal(ObjectOutput out) throws IOException {

        super.writeExternal(out);

        out.writeInt(number);
        out.writeInt(epoch);
        out.writeInt(paxosType);

        if(value == null) {

            out.writeInt(-1);

        } else {

            out.writeInt(value.length);
            out.write(value);

        }

        if(this.proof != null) {

            out.writeBoolean(true);
            out.writeObject(proof);

        }
        
        else {
            out.writeBoolean(false);
        }

    }

    // Implemented method of the Externalizable interface
    @Override
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {

        super.readExternal(in);

        number = in.readInt();
        epoch = in.readInt();
        paxosType = in.readInt();

        int toRead = in.readInt();

        if(toRead != -1) {

            value = new byte[toRead];

            do{

                toRead -= in.read(value, value.length-toRead, toRead);

            } while(toRead > 0);

        }

        boolean asProof = in.readBoolean();
        if (asProof) {
            
            proof = in.readObject();
        }
        
    }

    /**
     * Retrieves the epoch number to which this message belongs
     * @return Epoch to which this message belongs
     */
    public int getEpoch() {

        return epoch;

    }
    
    /**
     * Retrieves the value contained in the message.
     * @return The value
     */
    public byte[] getValue() {

        return value;

    }

    public void setProof(Object proof) {
        
        this.proof = proof;
    }
    
    /**
     * Returns the proof associated with a PROPOSE or COLLECT message
     * @return The proof
     */
    public Object getProof() {

        return proof;

    }

    /**
     * Returns the consensus ID of this message
     * @return Consensus ID of this message
     */
    public int getNumber() {

        return number;

    }

    /**
     * Returns this message type
     * @return This message type
     */
    public int getType() {

        return paxosType;

    }

    /**
     * Returns this message type as a verbose string
     * @return Message type
     */
    public String getPaxosVerboseType() {
        if (paxosType==MessageFactory.PROPOSE)
            return "PROPOSE";
        else if (paxosType==MessageFactory.ACCEPT)
            return "ACCEPT";
        else if (paxosType==MessageFactory.WRITE)
            return "WRITE";
        else
            return "";
    }

    @Override
    public String toString() {
        return "type="+getPaxosVerboseType()+", number="+getNumber()+", epoch="+
                getEpoch()+", from="+getSender();
    }

}