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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.dex.code.form;
     18 
     19 import com.android.dexgen.dex.code.DalvInsn;
     20 import com.android.dexgen.dex.code.InsnFormat;
     21 import com.android.dexgen.dex.code.TargetInsn;
     22 import com.android.dexgen.rop.code.RegisterSpecList;
     23 import com.android.dexgen.util.AnnotatedOutput;
     24 
     25 /**
     26  * Instruction format {@code 21t}. See the instruction format spec
     27  * for details.
     28  */
     29 public final class Form21t extends InsnFormat {
     30     /** {@code non-null;} unique instance of this class */
     31     public static final InsnFormat THE_ONE = new Form21t();
     32 
     33     /**
     34      * Constructs an instance. This class is not publicly
     35      * instantiable. Use {@link #THE_ONE}.
     36      */
     37     private Form21t() {
     38         // This space intentionally left blank.
     39     }
     40 
     41     /** {@inheritDoc} */
     42     @Override
     43     public String insnArgString(DalvInsn insn) {
     44         RegisterSpecList regs = insn.getRegisters();
     45         return regs.get(0).regString() + ", " + branchString(insn);
     46     }
     47 
     48     /** {@inheritDoc} */
     49     @Override
     50     public String insnCommentString(DalvInsn insn, boolean noteIndices) {
     51         return branchComment(insn);
     52     }
     53 
     54     /** {@inheritDoc} */
     55     @Override
     56     public int codeSize() {
     57         return 2;
     58     }
     59 
     60     /** {@inheritDoc} */
     61     @Override
     62     public boolean isCompatible(DalvInsn insn) {
     63         RegisterSpecList regs = insn.getRegisters();
     64 
     65         if (!((insn instanceof TargetInsn) &&
     66               (regs.size() == 1) &&
     67               unsignedFitsInByte(regs.get(0).getReg()))) {
     68             return false;
     69         }
     70 
     71         TargetInsn ti = (TargetInsn) insn;
     72         return ti.hasTargetOffset() ? branchFits(ti) : true;
     73     }
     74 
     75     /** {@inheritDoc} */
     76     @Override
     77     public boolean branchFits(TargetInsn insn) {
     78         int offset = insn.getTargetOffset();
     79 
     80         // Note: A zero offset would fit, but it is prohibited by the spec.
     81         return (offset != 0) && signedFitsInShort(offset);
     82     }
     83 
     84     /** {@inheritDoc} */
     85     @Override
     86     public InsnFormat nextUp() {
     87         return Form31t.THE_ONE;
     88     }
     89 
     90     /** {@inheritDoc} */
     91     @Override
     92     public void writeTo(AnnotatedOutput out, DalvInsn insn) {
     93         RegisterSpecList regs = insn.getRegisters();
     94         int offset = ((TargetInsn) insn).getTargetOffset();
     95 
     96         write(out,
     97               opcodeUnit(insn, regs.get(0).getReg()),
     98               (short) offset);
     99     }
    100 }
    101