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 java.util.Arrays;
022
023import org.apache.commons.compress.harmony.unpack200.bytecode.ByteCode;
024import org.apache.commons.compress.harmony.unpack200.bytecode.OperandManager;
025
026/**
027 * Lookup switch instruction form.
028 */
029public class LookupSwitchForm extends SwitchForm {
030
031    /**
032     * Constructs a new instance with the specified opcode, name, operandType and rewrite.
033     *
034     * @param opcode  index corresponding to the opcode's value.
035     * @param name    String printable name of the opcode.
036     */
037    public LookupSwitchForm(final int opcode, final String name) {
038        super(opcode, name);
039    }
040
041    @Override
042    public void setByteCodeOperands(final ByteCode byteCode, final OperandManager operandManager, final int codeLength) {
043        final int caseCount = operandManager.nextCaseCount();
044        final int defaultPc = operandManager.nextLabel();
045        final int[] caseValues = new int[caseCount];
046        Arrays.setAll(caseValues, i -> operandManager.nextCaseValues());
047        final int[] casePcs = new int[caseCount];
048        Arrays.setAll(casePcs, i -> operandManager.nextLabel());
049
050        final int[] labelsArray = new int[caseCount + 1];
051        labelsArray[0] = defaultPc;
052        System.arraycopy(casePcs, 0, labelsArray, 1, caseCount + 1 - 1);
053        byteCode.setByteCodeTargets(labelsArray);
054
055        // All this gets dumped into the rewrite bytes of the
056        // poor bytecode.
057
058        // Unlike most byte codes, the LookupSwitch is a
059        // variable-sized bytecode. Because of this, the
060        // rewrite array has to be defined here individually
061        // for each bytecode, rather than in the ByteCodeForm
062        // class.
063
064        // First, there's the bytecode. Then there are 0-3
065        // bytes of padding so that the first (default)
066        // label is on a 4-byte offset.
067        final int padLength = 3 - codeLength % 4;
068        final int rewriteSize = 1 + padLength + 4 // defaultbytes
069                + 4 // npairs
070                + 4 * caseValues.length + 4 * casePcs.length;
071
072        final int[] newRewrite = new int[rewriteSize];
073        int rewriteIndex = 0;
074
075        // Fill in what we can now
076        // opcode
077        newRewrite[rewriteIndex++] = byteCode.getOpcode();
078
079        // padding
080        for (int index = 0; index < padLength; index++) {
081            newRewrite[rewriteIndex++] = 0;
082        }
083
084        // defaultbyte
085        // This gets overwritten by fixUpByteCodeTargets
086        newRewrite[rewriteIndex++] = -1;
087        newRewrite[rewriteIndex++] = -1;
088        newRewrite[rewriteIndex++] = -1;
089        newRewrite[rewriteIndex++] = -1;
090
091        // npairs
092        final int npairsIndex = rewriteIndex;
093        setRewrite4Bytes(caseValues.length, npairsIndex, newRewrite);
094        rewriteIndex += 4;
095
096        // match-offset pairs
097        // The caseValues aren't overwritten, but the
098        // casePcs will get overwritten by fixUpByteCodeTargets
099        for (final int caseValue : caseValues) {
100            // match
101            setRewrite4Bytes(caseValue, rewriteIndex, newRewrite);
102            rewriteIndex += 4;
103            // offset
104            newRewrite[rewriteIndex++] = -1;
105            newRewrite[rewriteIndex++] = -1;
106            newRewrite[rewriteIndex++] = -1;
107            newRewrite[rewriteIndex++] = -1;
108        }
109        byteCode.setRewrite(newRewrite);
110    }
111}