org.eclipse.linuxtools.ctf.core/src/org/eclipse/linuxtools/internal/ctf/core/event/CTFCallsiteComparator.java

   1 /*******************************************************************************
   2  * Copyright (c) 2013 Ericsson
   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:
  10  *  Simon Delisle - Initial implementation
  11  *******************************************************************************/
  12
  13 package org.eclipse.linuxtools.internal.ctf.core.event;
  14
  15 import java.util.Comparator;
  16
  17 import org.eclipse.linuxtools.ctf.core.event.CTFCallsite;
  18
  19 /**
  20  * Comparator for CTFCallsite
  21  *
  22  * @author Simon Delisle
  23  * @since 3.0
  24  *
  25  */
  26 public class CTFCallsiteComparator implements Comparator<CTFCallsite> {
  27
  28     private static final long MASK32 = 0x00000000ffffffffL;
  29
  30     /*
  31      * The callsites will be sorted by calling addresses. To do this we take IPs
  32      * (instruction pointers) and compare them. Java only supports signed
  33      * operation and since memory addresses are unsigned, we will convert the
  34      * longs into integers that contain the high and low bytes and compare them.
  35      */
  36     @Override
  37     public int compare(CTFCallsite o1, CTFCallsite o2) {
  38         /*
  39          * mask32 is 32 zeros followed by 32 ones, when we bitwise and this it
  40          * will return the lower 32 bits
  41          */
  42
  43         long other = o2.getIp();
  44         /*
  45          * To get a high int: we downshift by 32 and bitwise and with the mask
  46          * to get rid of the sign
  47          *
  48          * To get the low int: we bitwise and with the mask.
  49          */
  50         long otherHigh = (other >> 32) & MASK32;
  51         long otherLow = other & MASK32;
  52         long ownHigh = (o1.getIp() >> 32) & MASK32;
  53         long ownLow = o1.getIp() & MASK32;
  54         /* are the high values different, if so ignore the lower values */
  55         if (ownHigh > otherHigh) {
  56             return 1;
  57         }
  58         if (ownHigh < otherHigh ) {
  59             return -1;
  60         }
  61         /* the high values are the same, compare the lower values */
  62         if (ownLow > otherLow) {
  63             return 1;
  64         }
  65         if (ownLow < otherLow) {
  66             return -1;
  67         }
  68         /* the values are identical */
  69         return 0;
  70     }
  71
  72 }