ntpv3impl.java

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package org.apache.commons.net.ntp;
/*
 * Copyright 2001-2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import java.net.DatagramPacket;

/***
 * Implementation of NtpV3Packet with methods converting Java objects to/from
 * the Network Time Protocol (NTP) data message header format described in RFC-1305.
 *
 * @author Naz Irizarry, MITRE Corp
 * @author Jason Mathews, MITRE Corp
 *
 * @version $Revision: 165675 $ $Date: 2005-05-02 15:09:55 -0500 (Mon, 02 May 2005) $
 */
public class NtpV3Impl implements NtpV3Packet
{

    private static final int MODE_INDEX = 0;
    private static final int MODE_SHIFT = 0;

    private static final int VERSION_INDEX = 0;
    private static final int VERSION_SHIFT = 3;

    private static final int LI_INDEX = 0;
    private static final int LI_SHIFT = 6;

    private static final int STRATUM_INDEX = 1;
    private static final int POLL_INDEX = 2;
    private static final int PRECISION_INDEX = 3;

    private static final int ROOT_DELAY_INDEX = 4;
    private static final int ROOT_DISPERSION_INDEX = 8;
    private static final int REFERENCE_ID_INDEX = 12;

    private static final int REFERENCE_TIMESTAMP_INDEX = 16;
    private static final int ORIGINATE_TIMESTAMP_INDEX = 24;
    private static final int RECEIVE_TIMESTAMP_INDEX = 32;
    private static final int TRANSMIT_TIMESTAMP_INDEX = 40;

    private static final int KEY_IDENTIFIER_INDEX = 48;
    private static final int MESSAGE_DIGEST = 54; /* len 16 bytes */

    private byte[] buf = new byte[48];

    private DatagramPacket dp;

    /** Creates a new instance of NtpV3Impl */
    public NtpV3Impl()
    {
    }

    /***
     * Returns mode as defined in RFC-1305 which is a 3-bit integer
     * whose value is indicated by the MODE_xxx parameters.
     *
     * @return mode as defined in RFC-1305.
     */
    public int getMode()
    {
        return (ui(buf[MODE_INDEX]) >> MODE_SHIFT) & 0x7;
    }

    /***
     * Return human-readable name of message mode type as described in
     * RFC 1305.
     * @return mode name as string.
     */
    public String getModeName()
    {
        return NtpUtils.getModeName(getMode());
    }

    /***
     * Set mode as defined in RFC-1305.
     * @param mode
     */
    public void setMode(int mode)
    {
        buf[MODE_INDEX] = (byte) (buf[MODE_INDEX] & 0xF8 | mode & 0x7);
    }

    /***
     * Returns leap indicator as defined in RFC-1305 which is a two-bit code:
     *	0=no warning
     *	1=last minute has 61 seconds
     *	2=last minute has 59 seconds
     *	3=alarm condition (clock not synchronized)
     *
     * @return leap indicator as defined in RFC-1305.
     */
    public int getLeapIndicator()
    {
        return (ui(buf[LI_INDEX]) >> LI_SHIFT) & 0x3;
    }

    /***
     * Set leap indicator as defined in RFC-1305.
     * @param li leap indicator.
     */
    public void setLeapIndicator(int li)
    {
        buf[LI_INDEX] = (byte) (buf[LI_INDEX] & 0x3F | ((li & 0x3) << LI_SHIFT));
    }

    /***
     * Returns poll interval as defined in RFC-1305, which is an eight-bit
     * signed integer indicating the maximum interval between successive
     * messages, in seconds to the nearest power of two (e.g. value of six
     * indicates an interval of 64 seconds. The values that can appear in
     * this field range from NTP_MINPOLL to NTP_MAXPOLL inclusive.
     *
     * @return poll interval as defined in RFC-1305.
     */
    public int getPoll()
    {
        return (int) (buf[POLL_INDEX]);
    }

    /***
     * Set poll interval as defined in RFC-1305.
     *
     * @param poll poll interval.
     */
    public void setPoll(int poll)
    {
        buf[POLL_INDEX] = (byte) (poll & 0xFF);
    }

    /***
     * Returns precision as defined in RFC-1305 encoded as an 8-bit signed
     * integer (seconds to nearest power of two).
     * Values normally range from -6 to -20.
     *
     * @return precision as defined in RFC-1305.
     */
    public int getPrecision()
    {
        return (int) buf[PRECISION_INDEX];
    }

    /***
     * Set precision as defined in RFC-1305.
     * @param precision
     */
    public void setPrecision(int precision)
    {
        buf[PRECISION_INDEX] = (byte) (precision & 0xFF);
    }

    /***
     * Returns NTP version number as defined in RFC-1305.
     *
     * @return NTP version number.
     */
    public int getVersion()
    {
        return (ui(buf[VERSION_INDEX]) >> VERSION_SHIFT) & 0x7;
    }

    /***
     * Set NTP version as defined in RFC-1305.
     *
     * @param version NTP version.
     */
    public void setVersion(int version)
    {
        buf[VERSION_INDEX] = (byte) (buf[VERSION_INDEX] & 0xC7 | ((version & 0x7) << VERSION_SHIFT));
    }

    /***
     * Returns Stratum as defined in RFC-1305, which indicates the stratum level
     * of the local clock, with values defined as follows: 0=unspecified,
     * 1=primary ref clock, and all others a secondary reference (via NTP).
     *
     * @return Stratum level as defined in RFC-1305.
     */
    public int getStratum()
    {
        return ui(buf[STRATUM_INDEX]);
    }

    /***
     * Set stratum level as defined in RFC-1305.
     *
     * @param stratum stratum level.
     */
    public void setStratum(int stratum)
    {
        buf[STRATUM_INDEX] = (byte) (stratum & 0xFF);
    }

    /***
     * Return root delay as defined in RFC-1305, which is the total roundtrip delay
     * to the primary reference source, in seconds. Values can take positive and
     * negative values, depending on clock precision and skew.
     *
     * @return root delay as defined in RFC-1305.
     */
    public int getRootDelay()
    {
        return getInt(ROOT_DELAY_INDEX);
    }

    /***
     * Return root delay as defined in RFC-1305 in milliseconds, which is
     * the total roundtrip delay to the primary reference source, in
     * seconds. Values can take positive and negative values, depending
     * on clock precision and skew.
     *
     * @return root delay in milliseconds
     */
    public double getRootDelayInMillisDouble()
    {
        double l = getRootDelay();
        return l / 65.536;
    }

    /***
     * Returns root dispersion as defined in RFC-1305.
     * @return root dispersion.
     */
    public int getRootDispersion()
    {
        return getInt(ROOT_DISPERSION_INDEX);
    }

    /***
     * Returns root dispersion (as defined in RFC-1305) in milliseconds.
     *
     * @return root dispersion in milliseconds
     */
    public long getRootDispersionInMillis()
    {
        long l = getRootDispersion();
        return (l * 1000) / 65536L;
    }

    /***
     * Returns root dispersion (as defined in RFC-1305) in milliseconds
     * as double precision value.
     *
     * @return root dispersion in milliseconds
     */
    public double getRootDispersionInMillisDouble()
    {
        double l = getRootDispersion();
        return l / 65.536;
    }

    /***
     * Set reference clock identifier field with 32-bit unsigned integer value.
     * See RFC-1305 for description.
     *
     * @param refId reference clock identifier.
     */
    public void setReferenceId(int refId)
    {
        for (int i = 3; i >= 0; i--) {
            buf[REFERENCE_ID_INDEX + i] = (byte) (refId & 0xff);
            refId >>>= 8; // shift right one-byte
        }
    }

    /***
     * Returns the reference id as defined in RFC-1305, which is
     * a 32-bit integer whose value is dependent on several criteria.
     *
     * @return the reference id as defined in RFC-1305.
     */
    public int getReferenceId()
    {
        return getInt(REFERENCE_ID_INDEX);
    }

    /***
     * Returns the reference id string. String cannot be null but
     * value is dependent on the version of the NTP spec supported
     * and stratum level. Value can be an empty string, clock type string,
     * IP address, or a hex string.