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.io.Opcodes; 20 import com.android.dx.rop.code.RegisterSpecList; 21 import com.android.dx.rop.code.SourcePosition; 22 import com.android.dx.util.AnnotatedOutput; 23 24 /** 25 * Pseudo-instruction which either turns into a {@code nop} or 26 * nothingness, in order to make the subsequent instruction have an 27 * even address. This is used to align (subsequent) instructions that 28 * require it. 29 */ 30 public final class OddSpacer extends VariableSizeInsn { 31 /** 32 * Constructs an instance. The output address of this instance is initially 33 * unknown ({@code -1}). 34 * 35 * @param position {@code non-null;} source position 36 */ OddSpacer(SourcePosition position)37 public OddSpacer(SourcePosition position) { 38 super(position, RegisterSpecList.EMPTY); 39 } 40 41 /** {@inheritDoc} */ 42 @Override codeSize()43 public int codeSize() { 44 return (getAddress() & 1); 45 } 46 47 /** {@inheritDoc} */ 48 @Override writeTo(AnnotatedOutput out)49 public void writeTo(AnnotatedOutput out) { 50 if (codeSize() != 0) { 51 out.writeShort(InsnFormat.codeUnit(Opcodes.NOP, 0)); 52 } 53 } 54 55 /** {@inheritDoc} */ 56 @Override withRegisters(RegisterSpecList registers)57 public DalvInsn withRegisters(RegisterSpecList registers) { 58 return new OddSpacer(getPosition()); 59 } 60 61 /** {@inheritDoc} */ 62 @Override argString()63 protected String argString() { 64 return null; 65 } 66 67 /** {@inheritDoc} */ 68 @Override listingString0(boolean noteIndices)69 protected String listingString0(boolean noteIndices) { 70 if (codeSize() == 0) { 71 return null; 72 } 73 74 return "nop // spacer"; 75 } 76 } 77