001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 * 017 */ 018package org.apache.bcel.generic; 019 020/** 021 * BranchHandle is returned by specialized InstructionList.append() whenever a 022 * BranchInstruction is appended. This is useful when the target of this 023 * instruction is not known at time of creation and must be set later 024 * via setTarget(). 025 * 026 * @see InstructionHandle 027 * @see Instruction 028 * @see InstructionList 029 */ 030public final class BranchHandle extends InstructionHandle { 031 032 // This is also a cache in case the InstructionHandle#swapInstruction() method is used 033 // See BCEL-273 034 private BranchInstruction bi; // An alias in fact, but saves lots of casts 035 036 037 private BranchHandle(final BranchInstruction i) { 038 super(i); 039 bi = i; 040 } 041 042 /** Factory method. 043 */ 044 static BranchHandle getBranchHandle( final BranchInstruction i ) { 045 return new BranchHandle(i); 046 } 047 048 049 /* Override InstructionHandle methods: delegate to branch instruction. 050 * Through this overriding all access to the private i_position field should 051 * be prevented. 052 */ 053 @Override 054 public int getPosition() { 055 return bi.getPosition(); 056 } 057 058 059 @Override 060 void setPosition( final int pos ) { 061 // Original code: i_position = bi.position = pos; 062 bi.setPosition(pos); 063 super.setPosition(pos); 064 } 065 066 067 @Override 068 protected int updatePosition( final int offset, final int max_offset ) { 069 final int x = bi.updatePosition(offset, max_offset); 070 super.setPosition(bi.getPosition()); 071 return x; 072 } 073 074 075 /** 076 * Pass new target to instruction. 077 */ 078 public void setTarget( final InstructionHandle ih ) { 079 bi.setTarget(ih); 080 } 081 082 083 /** 084 * Update target of instruction. 085 */ 086 public void updateTarget( final InstructionHandle old_ih, final InstructionHandle new_ih ) { 087 bi.updateTarget(old_ih, new_ih); 088 } 089 090 091 /** 092 * @return target of instruction. 093 */ 094 public InstructionHandle getTarget() { 095 return bi.getTarget(); 096 } 097 098 099 /** 100 * Set new contents. Old instruction is disposed and may not be used anymore. 101 */ 102 @Override // This is only done in order to apply the additional type check; could be merged with super impl. 103 public void setInstruction( final Instruction i ) { // TODO could be package-protected? 104 super.setInstruction(i); 105 if (!(i instanceof BranchInstruction)) { 106 throw new ClassGenException("Assigning " + i 107 + " to branch handle which is not a branch instruction"); 108 } 109 bi = (BranchInstruction) i; 110 } 111}