Caldavsync Sources: src/net/fortuna/ical4j/util/UidGenerator.java@fb9019fb1bf7

Import initial revisions of existing project AndroidCaldavSyncAdapater,
forked from upstream repository at 27e8a0f8495c92e0780d450bdf0c7cec77a03a55.

     1 /**

     2  * Copyright (c) 2012, Ben Fortuna

     3  * All rights reserved.

     4  *

     5  * Redistribution and use in source and binary forms, with or without

     6  * modification, are permitted provided that the following conditions

     7  * are met:

     8  *

     9  *  o Redistributions of source code must retain the above copyright

    10  * notice, this list of conditions and the following disclaimer.

    11  *

    12  *  o Redistributions in binary form must reproduce the above copyright

    13  * notice, this list of conditions and the following disclaimer in the

    14  * documentation and/or other materials provided with the distribution.

    15  *

    16  *  o Neither the name of Ben Fortuna nor the names of any other contributors

    17  * may be used to endorse or promote products derived from this software

    18  * without specific prior written permission.

    19  *

    20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

    21  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

    22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

    23  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR

    24  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

    25  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

    26  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

    27  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

    28  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

    29  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

    30  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    31  */

    32 package net.fortuna.ical4j.util;

    34 import java.net.SocketException;

    36 import net.fortuna.ical4j.model.DateTime;

    37 import net.fortuna.ical4j.model.property.Uid;

    39 /**

    40  * $Id$

    41  *

    42  * Created on 11/03/2007

    43  *

    44  * Generates {@link Uid} properties in a similar fashion to that recommended in section 4.8.4.7 of the specification.

    45  * @author Ben Fortuna

    46  */

    47 public class UidGenerator {

    49     private final String pid;

    51     private final HostInfo hostInfo;

    53     private static long lastMillis;

    55     /**

    56      * @param pid a unique process identifier for the host machine

    57      * @throws SocketException where host information cannot be retrieved

    58      */

    59     public UidGenerator(String pid) throws SocketException {

    60         this(new InetAddressHostInfo(), pid);

    61     }

    63     /**

    64      * @param hostInfo custom host information

    65      * @param pid a unique process identifier for the host machine

    66      */

    67     public UidGenerator(HostInfo hostInfo, String pid) {

    68         this.hostInfo = hostInfo;

    69         this.pid = pid;

    70     }

    72     /**

    73      * @return a unique component identifier

    74      */

    75     public Uid generateUid() {

    76         final StringBuffer b = new StringBuffer();

    77         b.append(uniqueTimestamp());

    78         b.append('-');

    79         b.append(pid);

    80         if (hostInfo != null) {

    81             b.append('@');

    82             b.append(hostInfo.getHostName());

    83         }

    84         return new Uid(b.toString());

    85     }

    87     /**

    88      * Generates a timestamp guaranteed to be unique for the current JVM instance.

    89      * @return a {@link DateTime} instance representing a unique timestamp

    90      */

    91     private static DateTime uniqueTimestamp() {

    92         long currentMillis;

    93         synchronized (UidGenerator.class) {

    94             currentMillis = System.currentTimeMillis();

    95             // guarantee uniqueness by ensuring timestamp is always greater

    96             // than the previous..

    97             if (currentMillis < lastMillis) {

    98                 currentMillis = lastMillis;

    99             }

   100             if (currentMillis - lastMillis < Dates.MILLIS_PER_SECOND) {

   101                 currentMillis += Dates.MILLIS_PER_SECOND;

   102             }

   103             lastMillis = currentMillis;

   104         }

   105         final DateTime timestamp = new DateTime(currentMillis);

   106         timestamp.setUtc(true);

   107         return timestamp;

   108     }

   109 }

Caldavsync Sources / file revision