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 BranchInstruction is appended. This is 022 * useful when the target of this instruction is not known at time of creation and must be set later via setTarget(). 023 * 024 * @see InstructionHandle 025 * @see Instruction 026 * @see InstructionList 027 */ 028public final class BranchHandle extends InstructionHandle { 029 030 /** 031 * Factory method. 032 */ 033 static BranchHandle getBranchHandle(final BranchInstruction i) { 034 return new BranchHandle(i); 035 } 036 037 // This is also a cache in case the InstructionHandle#swapInstruction() method is used 038 // See BCEL-273 039 private BranchInstruction bi; // An alias in fact, but saves lots of casts 040 041 private BranchHandle(final BranchInstruction i) { 042 super(i); 043 bi = i; 044 } 045 046 /* 047 * Override InstructionHandle methods: delegate to branch instruction. Through this overriding all access to the private 048 * i_position field should be prevented. 049 */ 050 @Override 051 public int getPosition() { 052 return bi.getPosition(); 053 } 054 055 /** 056 * @return target of instruction. 057 */ 058 public InstructionHandle getTarget() { 059 return bi.getTarget(); 060 } 061 062 /** 063 * Set new contents. Old instruction is disposed and may not be used anymore. 064 */ 065 @Override // This is only done in order to apply the additional type check; could be merged with super impl. 066 public void setInstruction(final Instruction i) { // TODO could be package-protected? 067 super.setInstruction(i); 068 if (!(i instanceof BranchInstruction)) { 069 throw new ClassGenException("Assigning " + i + " to branch handle which is not a branch instruction"); 070 } 071 bi = (BranchInstruction) i; 072 } 073 074 @Override 075 void setPosition(final int pos) { 076 // Original code: i_position = bi.position = pos; 077 bi.setPosition(pos); 078 super.setPosition(pos); 079 } 080 081 /** 082 * Pass new target to instruction. 083 */ 084 public void setTarget(final InstructionHandle ih) { 085 bi.setTarget(ih); 086 } 087 088 @Override 089 protected int updatePosition(final int offset, final int max_offset) { 090 final int x = bi.updatePosition(offset, max_offset); 091 super.setPosition(bi.getPosition()); 092 return x; 093 } 094 095 /** 096 * Update target of instruction. 097 */ 098 public void updateTarget(final InstructionHandle old_ih, final InstructionHandle new_ih) { 099 bi.updateTarget(old_ih, new_ih); 100 } 101}