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JGroups RAFT implementation
There is a newer version: 1.0.13.Final
package org.jgroups.protocols.raft;

import org.jgroups.Global;
import org.jgroups.util.Bits;
import org.jgroups.util.SizeStreamable;
import org.jgroups.util.Util;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

/**
 * An element in a log. Captures the term and command to be applied to the state machine
 * @author Bela Ban
 * @since  0.1
 */
public class LogEntry implements SizeStreamable {
    protected long    term;     // the term of this entry
    protected byte[]  command;  // the command (interpreted by the state machine)
    protected int     offset;   // may get removed (always 0)
    protected int     length;   // may get removed (always command.length)
    protected boolean internal; // if true, the contents of the buffer are an InternalCommand


    public LogEntry() {}

    public LogEntry(long term, byte[] command) {
        this(term, command, 0, command != null? command.length : 0);
    }

    public LogEntry(long term, byte[] command, int offset, int length) {
        this(term, command, offset, length, false);
    }


    public LogEntry(long term, byte[] command, int offset, int length, boolean internal) {
        this.term=term;
        this.command=command;
        this.offset=offset;
        this.length=length;
        this.internal=internal;
    }

    public long     term()              {return term;}
    public LogEntry term(long t)        {term=t; return this;}
    public byte[]   command()           {return command;}
    public int      offset()            {return offset;}
    public int      length()            {return length;}
    public boolean  internal()          {return internal;}
    public LogEntry internal(boolean b) {internal=b; return this;}

    public int serializedSize() {
        int retval=Bits.size(term) + Global.BYTE_SIZE*2;
        if(command != null)
            retval+=Global.INT_SIZE + length();
        return retval;
    }

    public void writeTo(DataOutput out) throws IOException {
        Bits.writeLongCompressed(term, out);
        Util.writeByteBuffer(command, offset, length, out);
        out.writeBoolean(internal);
    }

    public void readFrom(DataInput in) throws IOException {
        term=Bits.readLongCompressed(in);
        command=Util.readByteBuffer(in);
        offset=0;
        length=command != null? command.length : 0;
        internal=in.readBoolean();
    }

    public String toString() {
        StringBuilder str = new StringBuilder();
        str.append("term=").append(term).append(" (").append(command != null? command.length : 0).append(" bytes)");
        if(internal) str.append(" [internal]");
        return str.toString();
    }


}