    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
    021import org.apache.commons.compress.harmony.unpack200.bytecode.ByteCode;
    022import org.apache.commons.compress.harmony.unpack200.bytecode.CodeAttribute;
    023import org.apache.commons.compress.harmony.unpack200.bytecode.OperandManager;
    024
    025/**
    026 * This class implements the byte code form for those bytecodes which have label references (and only label references).
    027 */
    028public class LabelForm extends ByteCodeForm {
    029
    030    protected boolean widened;
    031
    032    /**
    033     * Constructs a new instance with the specified opcode, name, operandType and rewrite.
    034     *
    035     * @param opcode  index corresponding to the opcode's value.
    036     * @param name    String printable name of the opcode.
    037     * @param rewrite Operand positions (which will later be rewritten in ByteCodes) are indicated by -1.
    038     */
    039    public LabelForm(final int opcode, final String name, final int[] rewrite) {
    040        super(opcode, name, rewrite);
    041    }
    042
    043    /**
    044     * Constructs a new instance with the specified opcode, name, operandType and rewrite.
    045     *
    046     * @param opcode  index corresponding to the opcode's value.
    047     * @param name    String printable name of the opcode.
    048     * @param rewrite Operand positions (which will later be rewritten in ByteCodes) are indicated by -1.
    049     * @param widened TODO.
    050     */
    051    public LabelForm(final int opcode, final String name, final int[] rewrite, final boolean widened) {
    052        this(opcode, name, rewrite);
    053        this.widened = widened;
    054    }
    055
    056    /*
    057     * (non-Javadoc)
    058     *
    059     * @see org.apache.commons.compress.harmony.unpack200.bytecode.forms.ByteCodeForm#fixUpByteCodeTarget(org.apache.commons.
    060     * compress.harmony.unpack200.bytecode.ByteCode, org.apache.commons.compress.harmony.unpack200.bytecode.CodeAttribute)
    061     */
    062    @Override
    063    public void fixUpByteCodeTargets(final ByteCode byteCode, final CodeAttribute codeAttribute) {
    064        // LabelForms need to fix up the target of label operations
    065        final int originalTarget = byteCode.getByteCodeTargets()[0];
    066        final int sourceIndex = byteCode.getByteCodeIndex();
    067        final int absoluteInstructionTargetIndex = sourceIndex + originalTarget;
    068        final int targetValue = codeAttribute.byteCodeOffsets.get(absoluteInstructionTargetIndex).intValue();
    069        final int sourceValue = codeAttribute.byteCodeOffsets.get(sourceIndex).intValue();
    070        // The operand is the difference between the source instruction
    071        // and the destination instruction.
    072        byteCode.setOperandSigned2Bytes(targetValue - sourceValue, 0);
    073        if (widened) {
    074            byteCode.setNestedPositions(new int[][] { { 0, 4 } });
    075        } else {
    076            byteCode.setNestedPositions(new int[][] { { 0, 2 } });
    077        }
    078    }
    079
    080    /*
    081     * (non-Javadoc)
    082     *
    083     * @see org.apache.commons.compress.harmony.unpack200.bytecode.forms.ByteCodeForm#setByteCodeOperands(org.apache.commons.
    084     * compress.harmony.unpack200.bytecode.ByteCode, org.apache.commons.compress.harmony.unpack200.bytecode.OperandTable,
    085     * org.apache.commons.compress.harmony.unpack200.SegmentConstantPool)
    086     */
    087    @Override
    088    public void setByteCodeOperands(final ByteCode byteCode, final OperandManager operandManager, final int codeLength) {
    089        byteCode.setByteCodeTargets(new int[] { operandManager.nextLabel() });
    090        // The byte code operands actually get set later -
    091        // once we have all the bytecodes - in fixUpByteCodeTarget().
    092    }
    093}