Simplest Integer Encoder Example

Encoder.java

import org.apache.log4j.Logger;
import org.apache.mahout.math.Varint;

import java.io.*;

/**
 * @author Bohdan Mushkevych
 * Description: module presents tuple of two int values: alpha and beta
 */
class Tuple2I {
    protected int alpha;
    protected int beta;

    public Tuple2I(int alpha, int beta) {
        this.alpha = alpha;
        this.beta = beta;
    }

    /**
     * @return int presenting alpha
     */
    public int getAlpha() {
        return alpha;
    }

    /**
     * @return int presenting beta
     */
    public int getBeta() {
        return beta;
    }
}


/**
 * @author Bohdan Mushkevych
 * Description: module contains logic for VarInt integer encoding: conversion to and from the byte array
 */
public class Encoder {

    protected ByteArrayOutputStream baos = new ByteArrayOutputStream();
    protected DataOutputStream dos = new DataOutputStream(baos);
    private Logger log = Logger.getRootLogger();

    public Encoder() {
    }

    /**
     * Method generates byte[] for varargs of integers
     * @param args varargs of Integer type
     * @return generated value
     */
    protected byte[] getByteArray(int... args) {
        byte[] result = null;
        try {
            baos.reset();
            for (int i : args) {
                Varint.writeSignedVarInt(i, dos);
            }
            result = baos.toByteArray();
        } catch (IOException e) {
            log.error("Exception on Integer encoding", e);
        }
        return result;
    }

    /**
     * method decodes tuple from byte array
     * @param value encoded tuple
     * @return formed tuple instance
     */
    public Tuple2I decode(byte[] value) {
        ByteArrayInputStream bais = new ByteArrayInputStream(value);
        DataInputStream dis = new DataInputStream(bais);

        Tuple2I tuple = null;
        try {
            int alpha = Varint.readSignedVarInt(dis);
            int beta = Varint.readSignedVarInt(dis);
            tuple = new Tuple2I(alpha, beta);
        } catch (IOException e) {
            log.error("Exception on Integer decoding", e);
        }
        return tuple;
    }
}