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 17package com.android.dexgen.dex.code; 18 19import com.android.dexgen.rop.code.RegisterSpecList; 20import com.android.dexgen.rop.code.SourcePosition; 21import com.android.dexgen.util.AnnotatedOutput; 22 23/** 24 * Pseudo-instruction which either turns into a {@code nop} or 25 * nothingness, in order to make the subsequent instruction have an 26 * even address. This is used to align (subsequent) instructions that 27 * require it. 28 */ 29public final class OddSpacer extends VariableSizeInsn { 30 /** 31 * Constructs an instance. The output address of this instance is initially 32 * unknown ({@code -1}). 33 * 34 * @param position {@code non-null;} source position 35 */ 36 public OddSpacer(SourcePosition position) { 37 super(position, RegisterSpecList.EMPTY); 38 } 39 40 /** {@inheritDoc} */ 41 @Override 42 public int codeSize() { 43 return (getAddress() & 1); 44 } 45 46 /** {@inheritDoc} */ 47 @Override 48 public void writeTo(AnnotatedOutput out) { 49 if (codeSize() != 0) { 50 out.writeShort(InsnFormat.codeUnit(DalvOps.NOP, 0)); 51 } 52 } 53 54 /** {@inheritDoc} */ 55 @Override 56 public DalvInsn withRegisters(RegisterSpecList registers) { 57 return new OddSpacer(getPosition()); 58 } 59 60 /** {@inheritDoc} */ 61 @Override 62 protected String argString() { 63 return null; 64 } 65 66 /** {@inheritDoc} */ 67 @Override 68 protected String listingString0(boolean noteIndices) { 69 if (codeSize() == 0) { 70 return null; 71 } 72 73 return "nop // spacer"; 74 } 75} 76