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      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.dexgen.rop.cst;
     18 
     19 import com.android.dexgen.rop.type.Type;
     20 
     21 /**
     22  * Constant type to represent a known-{@code null} value.
     23  */
     24 public final class CstKnownNull extends CstLiteralBits {
     25     /** {@code non-null;} unique instance of this class */
     26     public static final CstKnownNull THE_ONE = new CstKnownNull();
     27 
     28     /**
     29      * Constructs an instance. This class is not publicly instantiable. Use
     30      * {@link #THE_ONE}.
     31      */
     32     private CstKnownNull() {
     33         // This space intentionally left blank.
     34     }
     35 
     36     /** {@inheritDoc} */
     37     @Override
     38     public boolean equals(Object other) {
     39         return (other instanceof CstKnownNull);
     40     }
     41 
     42     /** {@inheritDoc} */
     43     @Override
     44     public int hashCode() {
     45         return 0x4466757a;
     46     }
     47 
     48     /** {@inheritDoc} */
     49     @Override
     50     protected int compareTo0(Constant other) {
     51         return 0;
     52     }
     53 
     54     /** {@inheritDoc} */
     55     @Override
     56     public String toString() {
     57         return "known-null";
     58     }
     59 
     60     /** {@inheritDoc} */
     61     public Type getType() {
     62         return Type.KNOWN_NULL;
     63     }
     64 
     65     /** {@inheritDoc} */
     66     @Override
     67     public String typeName() {
     68         return "known-null";
     69     }
     70 
     71     /** {@inheritDoc} */
     72     @Override
     73     public boolean isCategory2() {
     74         return false;
     75     }
     76 
     77     /** {@inheritDoc} */
     78     public String toHuman() {
     79         return "null";
     80     }
     81 
     82     /** {@inheritDoc} */
     83     @Override
     84     public boolean fitsInInt() {
     85         // See comment in getIntBits().
     86         return true;
     87     }
     88 
     89     /**
     90      * {@inheritDoc}
     91      *
     92      * As "literal bits," a known-null is always represented as the
     93      * number zero.
     94      */
     95     @Override
     96     public int getIntBits() {
     97         return 0;
     98     }
     99 
    100     /**
    101      * {@inheritDoc}
    102      *
    103      * As "literal bits," a known-null is always represented as the
    104      * number zero.
    105      */
    106     @Override
    107     public long getLongBits() {
    108         return 0;
    109     }
    110 }
    111