FtpCmdPort.java

/*
 * ------------------------------------------------------------------------------
 * Hermes FTP Server
 * Copyright (c) 2005-2014 Lars Behnke
 * ------------------------------------------------------------------------------
 * 
 * This file is part of Hermes FTP Server.
 * 
 * Hermes FTP Server is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * Hermes FTP Server is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with Hermes FTP Server; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * ------------------------------------------------------------------------------
 */

package com.apporiented.hermesftp.cmd.impl;

import com.apporiented.hermesftp.cmd.AbstractFtpCmdPort;

/**
 * <b>DATA PORT (PORT)</b>
 * <p>
 * The argument is a HOST-PORT specification for the data port to be used in data connection. There
 * are defaults for both the user and server data ports, and under normal circumstances this command
 * and its reply are not needed. If this command is used, the argument is the concatenation of a
 * 32-bit internet host address and a 16-bit TCP port address. This address information is broken
 * into 8-bit fields and the value of each field is transmitted as a decimal number (in character
 * string representation). The fields are separated by commas. A port command would be: PORT
 * h1,h2,h3,h4,p1,p2 where h1 is the high order 8 bits of the internet host address.
 * <p>
 * <i>[Excerpt from RFC-959, Postel and Reynolds]</i>
 * </p>
 * 
 * @author Lars Behnke
 */
public class FtpCmdPort extends AbstractFtpCmdPort {

    private static final String DOT = ".";

    private int                 port;

    private String              addr;

    private String              lastArgs;

    /**
     * {@inheritDoc}
     */
    public String getHelp() {
        return "Sets port for active transfer.";
    }

    /**
     * {@inheritDoc}
     */
    protected String doReadIPAddr(String args) {
        if (!paramsParsed(args)) {
            parseParams(args);
        }
        return addr;
    }

    /**
     * {@inheritDoc}
     */
    protected int doReadPort(String args) {
        if (!paramsParsed(args)) {
            parseParams(args);
        }
        return port;
    }

    /**
     * {@inheritDoc}
     */
    protected int doReadProtocolIdx(String args) {
        return 1;
    }

    @SuppressWarnings("BooleanMethodIsAlwaysInverted")
    private boolean paramsParsed(String args) {
        return lastArgs != null && lastArgs.equals(args);
    }

    private void parseParams(String args) {
        try {
            lastArgs = args;
            String[] argParts = getArguments().split(",");
            int idx = 0;
            addr = argParts[idx++].trim() + DOT + argParts[idx++].trim() + DOT + argParts[idx++].trim() + DOT
                    + argParts[idx++].trim();
            int p1 = Integer.parseInt(argParts[idx++].trim()) & BYTE_MASK;
            int p2 = Integer.parseInt(argParts[idx++].trim()) & BYTE_MASK;
            port = (p1 << BYTE_LENGTH) + p2;
        } catch (Exception e) {
            throw new IllegalArgumentException("Invalid arguments: " + args);
        }
    }

}