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Apache Commons Compress software defines an API for working with
compression and archive formats. These include: bzip2, gzip, pack200,
lzma, xz, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4,
Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.compress.harmony.unpack200.bytecode.forms;
/**
* This abstract class implements the common code for instructions which have variable lengths. This is currently the
* *switch instructions and some wide (_w) instructions.
*/
public abstract class VariableInstructionForm extends ByteCodeForm {
public VariableInstructionForm(final int opcode, final String name) {
super(opcode, name);
}
/**
* 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, mid-low, low-byte encoding of the operand.
*
* Note that unlike the ByteCode setOperand* operations, this starts with an actual bytecode rewrite array (rather
* than a ByteCodeForm prototype rewrite 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, -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, rewrite) a second time will convert it to: {100, 0, 0, 0, 0, 200, 0, 0, 0, 0}
*
* @param operand int to set the rewrite bytes to
* @param rewrite int[] bytes to rewrite
*/
public void setRewrite4Bytes(final int operand, final int[] rewrite) {
int firstOperandPosition = -1;
// Find the first -1 in the rewrite array
for (int index = 0; index < rewrite.length - 3; index++) {
if ((rewrite[index] == -1) && (rewrite[index + 1] == -1) && (rewrite[index + 2] == -1)
&& (rewrite[index + 3] == -1)) {
firstOperandPosition = index;
break;
}
}
setRewrite4Bytes(operand, firstOperandPosition, rewrite);
}
/**
* This method writes operand directly into the rewrite array at index position specified.
*
* @param operand value to write
* @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.
* @param rewrite array to write into
*/
public void setRewrite4Bytes(final int operand, final int absPosition, final int[] rewrite) {
if (absPosition < 0) {
throw new Error("Trying to rewrite " + this + " but there is no room for 4 bytes");
}
final int byteCodeRewriteLength = rewrite.length;
if (absPosition + 3 > byteCodeRewriteLength) {
throw new Error("Trying to rewrite " + this + " with an int at position " + absPosition
+ " but this won't fit in the rewrite array");
}
rewrite[absPosition] = ((0xFF000000) & operand) >> 24;
rewrite[absPosition + 1] = ((0x00FF0000) & operand) >> 16;
rewrite[absPosition + 2] = ((0x0000FF00) & operand) >> 8;
rewrite[absPosition + 3] = ((0x000000FF) & operand);
}
/**
* This method writes operand directly into the rewrite array at index position specified.
*
* @param operand value to write
* @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.
* @param rewrite array to write into
*/
public void setRewrite2Bytes(final int operand, final int absPosition, final int[] rewrite) {
if (absPosition < 0) {
throw new Error("Trying to rewrite " + this + " but there is no room for 4 bytes");
}
final int byteCodeRewriteLength = rewrite.length;
if (absPosition + 1 > byteCodeRewriteLength) {
throw new Error("Trying to rewrite " + this + " with an int at position " + absPosition
+ " but this won't fit in the rewrite array");
}
rewrite[absPosition] = ((0xFF00) & operand) >> 8;
rewrite[absPosition + 1] = ((0x00FF) & operand);
}
}