001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * https://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019package org.apache.commons.compress.harmony.unpack200.bytecode.forms; 020 021/** 022 * This abstract class implements the common code for instructions which have variable lengths. This is currently the *switch instructions and some wide (_w) 023 * instructions. 024 */ 025public abstract class VariableInstructionForm extends ByteCodeForm { 026 027 /** 028 * Constructs a new instance with the specified opcode, name, operandType and rewrite. 029 * 030 * @param opcode index corresponding to the opcode's value. 031 * @param name String printable name of the opcode. 032 */ 033 public VariableInstructionForm(final int opcode, final String name) { 034 super(opcode, name); 035 } 036 037 /** 038 * This method writes operand directly into the rewrite array at index position specified. 039 * 040 * @param operand value to write 041 * @param absPosition position in array to write. Note that this is absolute position in the array, so one can overwrite the bytecode if one isn't careful. 042 * @param rewrite array to write into 043 */ 044 public void setRewrite2Bytes(final int operand, final int absPosition, final int[] rewrite) { 045 if (absPosition < 0) { 046 throw new Error("Trying to rewrite " + this + " but there is no room for 4 bytes"); 047 } 048 049 final int byteCodeRewriteLength = rewrite.length; 050 051 if (absPosition + 1 > byteCodeRewriteLength) { 052 throw new Error("Trying to rewrite " + this + " with an int at position " + absPosition + " but this won't fit in the rewrite array"); 053 } 054 055 rewrite[absPosition] = (0xFF00 & operand) >> 8; 056 rewrite[absPosition + 1] = 0x00FF & operand; 057 } 058 059 /** 060 * This method writes operand directly into the rewrite array at index position specified. 061 * 062 * @param operand value to write 063 * @param absPosition position in array to write. Note that this is absolute position in the array, so one can overwrite the bytecode if one isn't careful. 064 * @param rewrite array to write into 065 */ 066 public void setRewrite4Bytes(final int operand, final int absPosition, final int[] rewrite) { 067 if (absPosition < 0) { 068 throw new Error("Trying to rewrite " + this + " but there is no room for 4 bytes"); 069 } 070 071 final int byteCodeRewriteLength = rewrite.length; 072 073 if (absPosition + 3 > byteCodeRewriteLength) { 074 throw new Error("Trying to rewrite " + this + " with an int at position " + absPosition + " but this won't fit in the rewrite array"); 075 } 076 077 rewrite[absPosition] = (0xFF000000 & operand) >> 24; 078 rewrite[absPosition + 1] = (0x00FF0000 & operand) >> 16; 079 rewrite[absPosition + 2] = (0x0000FF00 & operand) >> 8; 080 rewrite[absPosition + 3] = 0x000000FF & operand; 081 } 082 083 /** 084 * Given an int operand, set the rewrite bytes for the next available operand position and the three immediately following it to a highest-byte, mid-high, 085 * mid-low, low-byte encoding of the operand. 086 * 087 * Note that unlike the ByteCode setOperand* operations, this starts with an actual bytecode rewrite array (rather than a ByteCodeForm prototype rewrite 088 * array). Also, this method overwrites -1 values in the rewrite array - so if you start with an array that looks like: {100, -1, -1, -1, -1, 200, -1, -1, 089 * -1, -1} then calling setRewrite4Bytes(0, rewrite) the first time will convert it to: {100, 0, 0, 0, 0, 200, -1, -1, -1, -1} Calling setRewrite4Bytes(0, 090 * rewrite) a second time will convert it to: {100, 0, 0, 0, 0, 200, 0, 0, 0, 0} 091 * 092 * @param operand int to set the rewrite bytes to 093 * @param rewrite int[] bytes to rewrite 094 */ 095 public void setRewrite4Bytes(final int operand, final int[] rewrite) { 096 int firstOperandPosition = -1; 097 098 // Find the first -1 in the rewrite array 099 for (int index = 0; index < rewrite.length - 3; index++) { 100 if (rewrite[index] == -1 && rewrite[index + 1] == -1 && rewrite[index + 2] == -1 && rewrite[index + 3] == -1) { 101 firstOperandPosition = index; 102 break; 103 } 104 } 105 setRewrite4Bytes(operand, firstOperandPosition, rewrite); 106 } 107}