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 * Table switch instruction form.
028 */
029public class TableSwitchForm 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 TableSwitchForm(final int opcode, final String name) {
038        super(opcode, name);
039    }
040
041    /*
042     * (non-Javadoc)
043     *
044     * @see org.apache.commons.compress.harmony.unpack200.bytecode.forms.SwitchForm#setByteCodeOperands(org.apache.commons.
045     * compress.harmony.unpack200.bytecode.ByteCode, org.apache.commons.compress.harmony.unpack200.bytecode.OperandManager, int)
046     */
047    @Override
048    public void setByteCodeOperands(final ByteCode byteCode, final OperandManager operandManager, final int codeLength) {
049        final int caseCount = operandManager.nextCaseCount();
050        final int defaultPc = operandManager.nextLabel();
051        int caseValue = -1;
052        caseValue = operandManager.nextCaseValues();
053
054        final int[] casePcs = new int[caseCount];
055        Arrays.setAll(casePcs, i -> operandManager.nextLabel());
056
057        final int[] labelsArray = new int[caseCount + 1];
058        labelsArray[0] = defaultPc;
059        System.arraycopy(casePcs, 0, labelsArray, 1, caseCount + 1 - 1);
060        byteCode.setByteCodeTargets(labelsArray);
061
062        final int lowValue = caseValue;
063        final int highValue = lowValue + caseCount - 1;
064        // All this gets dumped into the rewrite bytes of the
065        // poor bytecode.
066
067        // Unlike most byte codes, the TableSwitch is a
068        // variable-sized bytecode. Because of this, the
069        // rewrite array has to be defined here individually
070        // for each bytecode, rather than in the ByteCodeForm
071        // class.
072
073        // First, there's the bytecode. Then there are 0-3
074        // bytes of padding so that the first (default)
075        // label is on a 4-byte offset.
076        final int padLength = 3 - codeLength % 4;
077        final int rewriteSize = 1 + padLength + 4 // defaultbytes
078                + 4 // lowbyte
079                + 4 // highbyte
080                + 4 * casePcs.length;
081
082        final int[] newRewrite = new int[rewriteSize];
083        int rewriteIndex = 0;
084
085        // Fill in what we can now
086        // opcode
087        newRewrite[rewriteIndex++] = byteCode.getOpcode();
088
089        // padding
090        for (int index = 0; index < padLength; index++) {
091            newRewrite[rewriteIndex++] = 0;
092        }
093
094        // defaultbyte
095        // This gets overwritten by fixUpByteCodeTargets
096        newRewrite[rewriteIndex++] = -1;
097        newRewrite[rewriteIndex++] = -1;
098        newRewrite[rewriteIndex++] = -1;
099        newRewrite[rewriteIndex++] = -1;
100
101        // lowbyte
102        final int lowbyteIndex = rewriteIndex;
103        setRewrite4Bytes(lowValue, lowbyteIndex, newRewrite);
104        rewriteIndex += 4;
105
106        // highbyte
107        final int highbyteIndex = rewriteIndex;
108        setRewrite4Bytes(highValue, highbyteIndex, newRewrite);
109        rewriteIndex += 4;
110
111        // jump offsets
112        // The case_pcs will get overwritten by fixUpByteCodeTargets
113        for (int index = 0; index < caseCount; index++) {
114            // offset
115            newRewrite[rewriteIndex++] = -1;
116            newRewrite[rewriteIndex++] = -1;
117            newRewrite[rewriteIndex++] = -1;
118            newRewrite[rewriteIndex++] = -1;
119        }
120        byteCode.setRewrite(newRewrite);
121    }
122}