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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.dx.dex.code;
     18 
     19 import com.android.dx.rop.code.RegisterSpec;
     20 import com.android.dx.rop.code.RegisterSpecList;
     21 import com.android.dx.rop.code.SourcePosition;
     22 
     23 /**
     24  * Pseudo-instruction which is used to introduce a new local variable. That
     25  * is, an instance of this class in an instruction stream indicates that
     26  * starting with the subsequent instruction, the indicated variable
     27  * is bound.
     28  */
     29 public final class LocalStart extends ZeroSizeInsn {
     30     /**
     31      * {@code non-null;} register spec representing the local variable introduced
     32      * by this instance
     33      */
     34     private final RegisterSpec local;
     35 
     36     /**
     37      * Returns the local variable listing string for a single register spec.
     38      *
     39      * @param spec {@code non-null;} the spec to convert
     40      * @return {@code non-null;} the string form
     41      */
     42     public static String localString(RegisterSpec spec) {
     43         return spec.regString() + ' ' + spec.getLocalItem().toString() + ": " +
     44             spec.getTypeBearer().toHuman();
     45     }
     46 
     47     /**
     48      * Constructs an instance. The output address of this instance is initially
     49      * unknown ({@code -1}).
     50      *
     51      * @param position {@code non-null;} source position
     52      * @param local {@code non-null;} register spec representing the local
     53      * variable introduced by this instance
     54      */
     55     public LocalStart(SourcePosition position, RegisterSpec local) {
     56         super(position);
     57 
     58         if (local == null) {
     59             throw new NullPointerException("local == null");
     60         }
     61 
     62         this.local = local;
     63     }
     64 
     65     /** {@inheritDoc} */
     66     @Override
     67     public DalvInsn withRegisterOffset(int delta) {
     68         return new LocalStart(getPosition(), local.withOffset(delta));
     69     }
     70 
     71     /** {@inheritDoc} */
     72     @Override
     73     public DalvInsn withRegisters(RegisterSpecList registers) {
     74         return new LocalStart(getPosition(), local);
     75     }
     76 
     77     /**
     78      * Gets the register spec representing the local variable introduced
     79      * by this instance.
     80      *
     81      * @return {@code non-null;} the register spec
     82      */
     83     public RegisterSpec getLocal() {
     84         return local;
     85     }
     86 
     87     /** {@inheritDoc} */
     88     @Override
     89     protected String argString() {
     90         return local.toString();
     91     }
     92 
     93     /** {@inheritDoc} */
     94     @Override
     95     protected String listingString0(boolean noteIndices) {
     96         return "local-start " + localString(local);
     97     }
     98 }
     99