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

   1 /*******************************************************************************
   2  * Copyright (c) 2013, 2014 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.tracecompass.internal.ctf.core.event;
  14
  15 import java.util.Comparator;
  16
  17 import org.eclipse.tracecompass.ctf.core.event.CTFCallsite;
  18
  19 /**
  20  * Comparator for CTFCallsite
  21  *
  22  * @author Simon Delisle
  23  */
  24 public class CTFCallsiteComparator implements Comparator<CTFCallsite> {
  25
  26     private static final long MASK32 = 0x00000000ffffffffL;
  27
  28     /*
  29      * The callsites will be sorted by calling addresses. To do this we take IPs
  30      * (instruction pointers) and compare them. Java only supports signed
  31      * operation and since memory addresses are unsigned, we will convert the
  32      * longs into integers that contain the high and low bytes and compare them.
  33      */
  34     @Override
  35     public int compare(CTFCallsite o1, CTFCallsite o2) {
  36         /*
  37          * mask32 is 32 zeros followed by 32 ones, when we bitwise and this it
  38          * will return the lower 32 bits
  39          */
  40
  41         long other = o2.getIp();
  42         /*
  43          * To get a high int: we downshift by 32 and bitwise and with the mask
  44          * to get rid of the sign
  45          *
  46          * To get the low int: we bitwise and with the mask.
  47          */
  48         long otherHigh = (other >> 32) & MASK32;
  49         long otherLow = other & MASK32;
  50         long ownHigh = (o1.getIp() >> 32) & MASK32;
  51         long ownLow = o1.getIp() & MASK32;
  52         /* are the high values different, if so ignore the lower values */
  53         if (ownHigh > otherHigh) {
  54             return 1;
  55         }
  56         if (ownHigh < otherHigh ) {
  57             return -1;
  58         }
  59         /* the high values are the same, compare the lower values */
  60         if (ownLow > otherLow) {
  61             return 1;
  62         }
  63         if (ownLow < otherLow) {
  64             return -1;
  65         }
  66         /* the values are identical */
  67         return 0;
  68     }
  69
  70 }