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package com.github.ibole.infrastructure.common.utils;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.NetworkInterface;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.security.SecureRandom;
import java.util.Enumeration;

/*********************************************************************************************
 * .
 * 
 * 
 * 
 * Copyright 2016, iBole Inc. All rights reserved.
 * 
 * 

 * 
 *********************************************************************************************/

/**
 * Get the machine identifier from mac address.
 * 
 *
 */
public class MachineUtil {
  private static final Logger logger = LoggerFactory.getLogger(MachineUtil.class.getName());
  private static final int MACHINE_IDENTIFIER = createMachineIdentifier();

  public static int getMachineIdentifier() {
    return MACHINE_IDENTIFIER;
  }

  /**
   * Get the machine identifier from mac address
   *
   * @see ObjectId.java
   */
  private static int createMachineIdentifier() {
    // build a 2-byte machine piece based on NICs info
    int machinePiece;
    try {
      StringBuilder sb = new StringBuilder();
      Enumeration e = NetworkInterface.getNetworkInterfaces();

      if (e != null) {
        while (e.hasMoreElements()) {
          NetworkInterface ni = e.nextElement();
          sb.append(ni.toString());
          byte[] mac = ni.getHardwareAddress();
          if (mac != null) {
            ByteBuffer bb = ByteBuffer.wrap(mac);
            try {
              sb.append(bb.getChar());
              sb.append(bb.getChar());
              sb.append(bb.getChar());
            } catch (BufferUnderflowException shortHardwareAddressException) { // NOPMD
              // mac with less than 6 bytes. continue
            }
          }
        }
      }

      machinePiece = sb.toString().hashCode();
    } catch (Throwable ex) {
      // exception sometimes happens with IBM JVM, use random
      machinePiece = (new SecureRandom().nextInt());
      logger.warn(
          "Failed to get machine identifier from network interface, using random number instead",
          ex);
    }
    return machinePiece;
  }
}