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 */ 017package org.apache.commons.compress.harmony.unpack200.bytecode.forms; 018 019/** 020 * This abstract class implements the common code for instructions which have variable lengths. This is currently the *switch instructions and some wide (_w) 021 * instructions. 022 */ 023public abstract class VariableInstructionForm extends ByteCodeForm { 024 025 public VariableInstructionForm(final int opcode, final String name) { 026 super(opcode, name); 027 } 028 029 /** 030 * This method writes operand directly into the rewrite array at index position specified. 031 * 032 * @param operand value to write 033 * @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. 034 * @param rewrite array to write into 035 */ 036 public void setRewrite2Bytes(final int operand, final int absPosition, final int[] rewrite) { 037 if (absPosition < 0) { 038 throw new Error("Trying to rewrite " + this + " but there is no room for 4 bytes"); 039 } 040 041 final int byteCodeRewriteLength = rewrite.length; 042 043 if (absPosition + 1 > byteCodeRewriteLength) { 044 throw new Error("Trying to rewrite " + this + " with an int at position " + absPosition + " but this won't fit in the rewrite array"); 045 } 046 047 rewrite[absPosition] = (0xFF00 & operand) >> 8; 048 rewrite[absPosition + 1] = 0x00FF & operand; 049 } 050 051 /** 052 * This method writes operand directly into the rewrite array at index position specified. 053 * 054 * @param operand value to write 055 * @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. 056 * @param rewrite array to write into 057 */ 058 public void setRewrite4Bytes(final int operand, final int absPosition, final int[] rewrite) { 059 if (absPosition < 0) { 060 throw new Error("Trying to rewrite " + this + " but there is no room for 4 bytes"); 061 } 062 063 final int byteCodeRewriteLength = rewrite.length; 064 065 if (absPosition + 3 > byteCodeRewriteLength) { 066 throw new Error("Trying to rewrite " + this + " with an int at position " + absPosition + " but this won't fit in the rewrite array"); 067 } 068 069 rewrite[absPosition] = (0xFF000000 & operand) >> 24; 070 rewrite[absPosition + 1] = (0x00FF0000 & operand) >> 16; 071 rewrite[absPosition + 2] = (0x0000FF00 & operand) >> 8; 072 rewrite[absPosition + 3] = 0x000000FF & operand; 073 } 074 075 /** 076 * 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, 077 * mid-low, low-byte encoding of the operand. 078 * 079 * Note that unlike the ByteCode setOperand* operations, this starts with an actual bytecode rewrite array (rather than a ByteCodeForm prototype rewrite 080 * 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, 081 * -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, 082 * rewrite) a second time will convert it to: {100, 0, 0, 0, 0, 200, 0, 0, 0, 0} 083 * 084 * @param operand int to set the rewrite bytes to 085 * @param rewrite int[] bytes to rewrite 086 */ 087 public void setRewrite4Bytes(final int operand, final int[] rewrite) { 088 int firstOperandPosition = -1; 089 090 // Find the first -1 in the rewrite array 091 for (int index = 0; index < rewrite.length - 3; index++) { 092 if (rewrite[index] == -1 && rewrite[index + 1] == -1 && rewrite[index + 2] == -1 && rewrite[index + 3] == -1) { 093 firstOperandPosition = index; 094 break; 095 } 096 } 097 setRewrite4Bytes(operand, firstOperandPosition, rewrite); 098 } 099}