org.eclipse.linuxtools.ctf.core/src/org/eclipse/linuxtools/ctf/core/trace/Utils.java

   1 /*******************************************************************************
   2  * Copyright (c) 2011, 2013 Ericsson, Ecole Polytechnique de Montreal and others
   3  *
   4  * All rights reserved. This program and the accompanying materials are made
   5  * available under the terms of the Eclipse Public License v1.0 which
   6  * accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors: Matthew Khouzam - Initial API and implementation
  10  * Contributors: Simon Marchi - Initial API and implementation
  11  *******************************************************************************/
  12
  13 package org.eclipse.linuxtools.ctf.core.trace;
  14
  15 import java.util.UUID;
  16
  17 /**
  18  * Various utilities.
  19  *
  20  * @version 1.0
  21  * @author Matthew Khouzam
  22  * @author Simon Marchi
  23  */
  24 public class Utils {
  25
  26     private Utils() {}
  27
  28     // ------------------------------------------------------------------------
  29     // Constants
  30     // ------------------------------------------------------------------------
  31
  32     /**
  33      * CTF magic number. (sort of looks like CTF CTF CT)
  34      */
  35     public static final int CTF_MAGIC = 0xC1FC1FC1;
  36
  37     /**
  38      * TSDL magic number. (sort of looks like TSDL LSDT)
  39      */
  40     public static final int TSDL_MAGIC = 0x75D11D57;
  41
  42     /**
  43      * TSDL magic number length in bytes.
  44      */
  45     public static final int TSDL_MAGIC_LEN = 4;
  46
  47     /**
  48      * Directory separator on the current platform.
  49      */
  50     public static final String SEPARATOR = System.getProperty("file.separator"); //$NON-NLS-1$
  51
  52     /**
  53      * Length in bytes of a UUID value.
  54      */
  55     public static final int UUID_LEN = 16;
  56
  57     // ------------------------------------------------------------------------
  58     // Operations
  59     // ------------------------------------------------------------------------
  60
  61     /**
  62      * Performs an unsigned long comparison on two unsigned long numbers.
  63      *
  64      * <strong> As Java does not support unsigned types and arithmetic, parameters
  65      *       are received encoded as a signed long (two-complement) but the
  66      *       operation is an unsigned comparator.</strong>
  67      *
  68      * @param left
  69      *            Left operand of the comparator.
  70      * @param right
  71      *            Right operand of the comparator.
  72      * @return -1 if left &lt; right, 1 if left &gt; right, 0 if left == right.
  73      */
  74     public static int unsignedCompare(long left, long right) {
  75         /*
  76          * This method assumes that the arithmetic overflow on signed
  77          * integer wrap on a circular domain (modulo arithmetic in
  78          * two-complement), which is the defined behavior in Java.
  79          *
  80          * This idea is to rotate the domain by the length of the negative
  81          * space, and then use the signed operator.
  82          */
  83         final long a = left + Long.MIN_VALUE;
  84         final long b = right + Long.MIN_VALUE;
  85         if (a < b) {
  86             return -1;
  87         } else if (a > b) {
  88             return 1;
  89         }
  90         return 0;
  91     }
  92
  93     /**
  94      * Creates a UUID object from an array of 16 bytes.
  95      *
  96      * @param bytes
  97      *            Array of 16 bytes.
  98      * @return A UUID object.
  99      */
 100     public static UUID makeUUID(byte bytes[]) {
 101         long high = 0;
 102         long low = 0;
 103
 104         assert (bytes.length == Utils.UUID_LEN);
 105
 106         for (int i = 0; i < 8; i++) {
 107             low = (low << 8) | (bytes[i + 8] & 0xFF);
 108             high = (high << 8) | (bytes[i] & 0xFF);
 109         }
 110
 111         UUID uuid = new UUID(high, low);
 112
 113         return uuid;
 114     }
 115
 116 }