idbytes.java

JXTA&#8482 is a set of open, generalized peer-to-peer (P2P) protocols that allow any networked devi

/*
 * Copyright (c) 2001-2007 Sun Microsystems, Inc.  All rights reserved.
 *  
 *  The Sun Project JXTA(TM) Software License
 *  
 *  Redistribution and use in source and binary forms, with or without 
 *  modification, are permitted provided that the following conditions are met:
 *  
 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *  
 *  2. Redistributions in binary form must reproduce the above copyright notice, 
 *     this list of conditions and the following disclaimer in the documentation 
 *     and/or other materials provided with the distribution.
 *  
 *  3. The end-user documentation included with the redistribution, if any, must 
 *     include the following acknowledgment: "This product includes software 
 *     developed by Sun Microsystems, Inc. for JXTA(TM) technology." 
 *     Alternately, this acknowledgment may appear in the software itself, if 
 *     and wherever such third-party acknowledgments normally appear.
 *  
 *  4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must 
 *     not be used to endorse or promote products derived from this software 
 *     without prior written permission. For written permission, please contact 
 *     Project JXTA at http://www.jxta.org.
 *  
 *  5. Products derived from this software may not be called "JXTA", nor may 
 *     "JXTA" appear in their name, without prior written permission of Sun.
 *  
 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
 *  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 
 *  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SUN 
 *  MICROSYSTEMS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
 *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
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 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 
 *  EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *  
 *  JXTA is a registered trademark of Sun Microsystems, Inc. in the United 
 *  States and other countries.
 *  
 *  Please see the license information page at :
 *  <http://www.jxta.org/project/www/license.html> for instructions on use of 
 *  the license in source files.
 *  
 *  ====================================================================
 *  
 *  This software consists of voluntary contributions made by many individuals 
 *  on behalf of Project JXTA. For more information on Project JXTA, please see 
 *  http://www.jxta.org.
 *  
 *  This license is based on the BSD license adopted by the Apache Foundation. 
 */

package net.jxta.impl.id.UUID;


import java.io.Serializable;
import java.util.Arrays;
import java.util.zip.Checksum;
import java.util.zip.CRC32;


/**
 * Maintains the internal representation of a 'uuid' JXTA ID.
 *
 * @see net.jxta.id.IDFactory
 * @see net.jxta.impl.id.UUID.IDFormat
 * @see <a href="https://jxta-spec.dev.java.net/nonav/JXTAProtocols.html#refimpls-ids-jiuft" target="_blank">JXTA Protocols Specification : UUID ID Format</a>
 */
public final class IDBytes implements Serializable {
    
    /**
     *  The bytes.
     */
    public final byte[] bytes;
    
    /**
     *  The cached hash value for this object
     */
    protected transient int cachedHash = 0;
    
    /**
     *  Constructs a new byte representation. This constructor initializes only
     *  the flag fields of the ID.
     *
     */
    public IDBytes() {
        this.bytes = new byte[ IDFormat.IdByteArraySize ];
    }
    
    /**
     *  Constructs a new byte representation. This constructor initializes only
     *  the flag fields of the ID.
     */
    public IDBytes(byte type) {
        this();
        this.bytes[IDFormat.flagsOffset + IDFormat.flagsIdTypeOffset] = type;
    }
    
    /**
     * {@inheritDoc}
     */
    @Override
    public boolean equals(Object target) {
        if (this == target) {
            return true;
        }
        
        if (target instanceof IDBytes) {
            IDBytes asIDBytes = (IDBytes) target;

            return Arrays.equals(bytes, asIDBytes.bytes);
        } else {
            return false;
        }
    }
    
    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode() {
        int result = cachedHash;
        
        if (0 == result) {
            // There is a very small chance that this
            Checksum crc = new CRC32();

            crc.update(bytes, 0, bytes.length);

            cachedHash = (int) crc.getValue();           
            cachedHash = (0 == cachedHash) ? 1 : cachedHash;
            
            result = cachedHash;
        }
        
        return result;
    }
    
    /**
     * Returns a string representation of the ID bytes. The bytes are encoded
     * in hex ASCII format with two characters per byte. The pad bytes between
     * the primary id portion and the flags field are omitted.
     *
     * @return	String containing the unique value of this ID.
     */
    @Override
    public String toString() {
        return getUniqueValue().toString();
    }
    
    /**
     *  Private replacement for toHexString since we need the leading 0 digits.
     *  Returns a char array containing byte value encoded as 2 hex chars.
     *
     *  @param  theByte a byte containing the value to be encoded.
     *  @return	char[] containing byte value encoded as 2 hex characters.
     */
    private static char[] toHexDigits(byte theByte) {
        final char[] HEXDIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
        char result[] = new char[2];
                
        result[0] = HEXDIGITS[(theByte >>> 4) & 15];
        result[1] = HEXDIGITS[theByte & 15];
                
        return result;
    }
    
    /**
     *  Return an object containing the unique value of the ID. This object must
     *  provide implementations of toString() and hashCode() that are canonical
     *  and consistent from run-to-run given the same input values. Beyond
     *  this nothing should be assumed about the nature of this object. For some
     *  implementations the object returned may be the same as provided.
     *
     *  @return	Object which can provide canonical representations of the ID.
     */
    public Object getUniqueValue() {
        StringBuilder encoded = new StringBuilder(144);
        int lastIndex;

        // find the last non-zero index.
        for (lastIndex = IDFormat.flagsOffset - 1; lastIndex > 0; lastIndex--) {
            if (0 != bytes[lastIndex]) {
                break;
            }
        }
        
        // build the string.
        for (int eachByte = 0; eachByte <= lastIndex; eachByte++) {
            char[] asHex = toHexDigits(bytes[eachByte]);

            encoded.append(asHex);
        }
        
        // append the flags field        
        for (int eachFlagByte = IDFormat.flagsOffset; eachFlagByte < IDFormat.IdByteArraySize; eachFlagByte++) {
            char asHex[] = toHexDigits(bytes[eachFlagByte]);
            
            encoded.append(asHex);
        }

        return encoded.toString();
    }
    
    /**
     *  Insert a long value into the byte array. The long is stored in
     *  big-endian order into the byte array beginning at the specified index.
     *
     *  @param offset location within the byte array to insert.
     *  @param value value to be inserted.
     */
    public void longIntoBytes(int offset, long value) {
        if ((offset < 0) || ((offset + 8) > IDFormat.IdByteArraySize)) {
            throw new IndexOutOfBoundsException("Bad offset");
        }
        
        for (int eachByte = 0; eachByte < 8; eachByte++) {
            bytes[eachByte + offset] = (byte) (value >> ((7 - eachByte) * 8L));
        }
        
        cachedHash = 0;
    }
    
    /**
     *  Return the long value of a portion of the byte array. The long is
     *  retrieved in big-endian order from the byte array at the specified
     *  offset.
     *
     *  @param offset location within the byte array to extract.
     *  @return long value extracted from the byte array.
     */
    public long bytesIntoLong(int offset) {
        if ((offset < 0) || ((offset + 8) > IDFormat.IdByteArraySize)) {
            throw new IndexOutOfBoundsException("Bad offset");
        }
        
        long result = 0L;
        
        for (int eachByte = 0; eachByte < 8; eachByte++) {
            result |= ((long) (bytes[eachByte + offset] & 0xff)) << ((7 - eachByte) * 8L);
        }
        
        return result;
    }
}