1 /*
   2  * Copyright (c) 2015, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package org.graalvm.word;
  26 
  27 /**
  28  * Utility methods on Pointers.
  29  */
  30 public final class PointerUtils {
  31 
  32     private PointerUtils() {
  33         // This is a class of static methods, so no need for any instances.
  34     }
  35 
  36     /**
  37      * The value of a null Pointer.
  38      *
  39      * @return A null Pointer value.
  40      */
  41     @SuppressWarnings("unchecked")
  42     public static <T extends PointerBase> T nullPointer() {
  43         return (T) WordFactory.zero();
  44     }
  45 
  46     /**
  47      * Predicate to check for the null Pointer value.
  48      *
  49      * @return Whether that Pointer is the null Pointer.
  50      */
  51     public static boolean isNull(ComparableWord that) {
  52         return that.equal(nullPointer());
  53     }
  54 
  55     /**
  56      * Predicate to check for a non-null Pointer value.
  57      *
  58      * @return Whether that Pointer is not the null Pointer.
  59      */
  60     public static boolean isNonNull(ComparableWord that) {
  61         return that.notEqual(nullPointer());
  62     }
  63 
  64     /**
  65      * Round a Pointer down to the nearest smaller multiple.
  66      *
  67      * @param that The Pointer to be rounded up.
  68      * @param multiple The multiple to which that Pointer should be decreased.
  69      * @return That Pointer, but rounded down.
  70      */
  71     public static Pointer roundDown(PointerBase that, Unsigned multiple) {
  72         return (Pointer) UnsignedUtils.roundDown((Unsigned) that, multiple);
  73     }
  74 
  75     /**
  76      * Round a Pointer up to the nearest larger multiple.
  77      *
  78      * @param that The Pointer to be rounded up.
  79      * @param multiple The multiple to which that Pointer should be increased.
  80      * @return That Pointer, but rounded up.
  81      */
  82     public static Pointer roundUp(PointerBase that, Unsigned multiple) {
  83         return (Pointer) UnsignedUtils.roundUp((Unsigned) that, multiple);
  84     }
  85 
  86     /**
  87      * Check that a Pointer is an even multiple.
  88      *
  89      * @param that The Pointer to be verified as a multiple.
  90      * @param multiple The multiple against which the Pointer should be verified.
  91      * @return true if that Pointer is a multiple, false otherwise.
  92      */
  93     public static boolean isAMultiple(PointerBase that, Unsigned multiple) {
  94         return that.equal(PointerUtils.roundDown(that, multiple));
  95     }
  96 
  97     /**
  98      * Return the distance between two Pointers.
  99      *
 100      * @param pointer1 A first Pointer.
 101      * @param pointer2 A second Pointer.
 102      * @return The distance in bytes between the two Pointers.
 103      */
 104     public static Unsigned absoluteDifference(PointerBase pointer1, PointerBase pointer2) {
 105         Pointer p1 = (Pointer) pointer1;
 106         Pointer p2 = (Pointer) pointer2;
 107         final Unsigned result;
 108         if (p1.aboveOrEqual(p2)) {
 109             result = p1.subtract(p2);
 110         } else {
 111             result = p2.subtract(p1);
 112         }
 113         return result;
 114     }
 115 
 116     /**
 117      * The minimum of two Pointers.
 118      *
 119      * @param x A Pointer.
 120      * @param y Another Pointer.
 121      * @return The whichever Pointer is smaller.
 122      */
 123     public static <T extends PointerBase> T min(T x, T y) {
 124         return (((Pointer) x).belowOrEqual((Pointer) y)) ? x : y;
 125     }
 126 
 127     /**
 128      * The maximum of two Pointers.
 129      *
 130      * @param x A Pointer.
 131      * @param y Another Pointer.
 132      * @return The whichever Pointer is larger.
 133      */
 134     public static <T extends PointerBase> T max(T x, T y) {
 135         return (((Pointer) x).aboveOrEqual((Pointer) y)) ? x : y;
 136     }
 137 }