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The core module of Pcap4J.
There is a newer version: 2.0.0-alpha.6
/*_##########################################################################
  _##
  _##  Copyright (C) 2014  Pcap4J.org
  _##
  _##########################################################################
*/

package org.pcap4j.packet;

import java.io.ObjectStreamException;
import org.pcap4j.packet.TcpPacket.TcpOption;
import org.pcap4j.packet.namednumber.TcpOptionKind;
import org.pcap4j.util.ByteArrays;

/**
 * @author Kaito Yamada
 * @since pcap4j 1.2.0
 */
public final class TcpSackPermittedOption implements TcpOption {

  /*
   * http://tools.ietf.org/html/rfc2018
   *
   *   +---------+---------+
   *   | Kind=4  | Length=2|
   *   +---------+---------+
   */

  /** */
  private static final long serialVersionUID = -5364948716212977767L;

  private static final TcpSackPermittedOption INSTANCE = new TcpSackPermittedOption();

  private static final TcpOptionKind kind = TcpOptionKind.SACK_PERMITTED;
  private static final byte length = 2;

  private TcpSackPermittedOption() {}

  /** @return the singleton instance of TcpSackPermittedOption. */
  public static TcpSackPermittedOption getInstance() {
    return INSTANCE;
  }

  /**
   * A static factory method. This method validates the arguments by {@link
   * ByteArrays#validateBounds(byte[], int, int)}, which may throw exceptions undocumented here.
   *
   * @param rawData rawData
   * @param offset offset
   * @param length length
   * @return the singleton instance of TcpSackPermittedOption.
   * @throws IllegalRawDataException if parsing the raw data fails.
   */
  public static TcpSackPermittedOption newInstance(byte[] rawData, int offset, int length)
      throws IllegalRawDataException {
    ByteArrays.validateBounds(rawData, offset, length);

    if (length < 2) {
      StringBuilder sb = new StringBuilder(50);
      sb.append("The raw data length must be more than 1. rawData: ")
          .append(ByteArrays.toHexString(rawData, " "))
          .append(", offset: ")
          .append(offset)
          .append(", length: ")
          .append(length);
      throw new IllegalRawDataException(sb.toString());
    }
    if (rawData[offset] != kind.value()) {
      StringBuilder sb = new StringBuilder(100);
      sb.append("The kind must be: ")
          .append(kind.valueAsString())
          .append(" rawData: ")
          .append(ByteArrays.toHexString(rawData, " "))
          .append(", offset: ")
          .append(offset)
          .append(", length: ")
          .append(length);
      throw new IllegalRawDataException(sb.toString());
    }
    if (rawData[1 + offset] != 2) {
      throw new IllegalRawDataException(
          "The value of length field must be 2 but: " + rawData[1 + offset]);
    }
    return INSTANCE;
  }

  @Override
  public TcpOptionKind getKind() {
    return kind;
  }

  /** @return length */
  public byte getLength() {
    return length;
  }

  /** @return length */
  public int getLengthAsInt() {
    return 0xFF & length;
  }

  @Override
  public int length() {
    return 2;
  }

  @Override
  public byte[] getRawData() {
    byte[] rawData = new byte[length()];
    rawData[0] = kind.value();
    rawData[1] = length;
    return rawData;
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("[Kind: ").append(kind);
    sb.append("] [Length: ").append(getLengthAsInt()).append(" bytes]");
    return sb.toString();
  }

  // Override deserializer to keep singleton
  @SuppressWarnings("static-method")
  private Object readResolve() throws ObjectStreamException {
    return INSTANCE;
  }
}